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Occurrence, Fate, and Transport of Contaminants in Indoor Air and Atmosphere

Enhanced Organic Nitrate Formation from Peroxy Radicals in the Condensed Phase
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  • Victoria P. Barber*
    Victoria P. Barber
    Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
    *Email: [email protected]
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    Orcidhttps://orcid.org/0000-0003-4543-4657
  • Lexy N. LeMar
    Lexy N. LeMar
    Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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  • Yaowei Li
    Yaowei Li
    John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States
    More by Yaowei Li
    Orcidhttps://orcid.org/0000-0003-0725-6108
  • Jonathan W. Zheng
    Jonathan W. Zheng
    Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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  • Frank N. Keutsch
    Frank N. Keutsch
    John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States
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    Orcidhttps://orcid.org/0000-0002-1442-6200
  • Jesse H. Kroll*
    Jesse H. Kroll
    Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
    Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
    *Email: [email protected]
    More by Jesse H. Kroll
    Orcidhttps://orcid.org/0000-0002-6275-521X
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Environmental Science & Technology Letters

Cite this: Environ. Sci. Technol. Lett. 2024, 11, 9, 975–980
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https://doi.org/10.1021/acs.estlett.4c00473
Published August 13, 2024

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Abstract

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Organic alkoxy (RO) and peroxy (RO2) radicals are key intermediates in multiphase atmospheric oxidation chemistry, though most of the study of their chemistry has focused on the gas phase. To better understand how radical chemistry may vary across different phases, we examine the chemistry of a model system, the 1-pentoxy radical, in three phases: the aqueous phase, the condensed organic phase, and the gas phase. In each phase, we generate the 1-pentoxy radical from the photolysis of n-pentyl nitrite, run the chemistry under conditions in which RO2 radicals react with NO, and detect the products in real time using an ammonium chemical ionization mass spectrometer (NH4+ CIMS). The condensed-phase chemistry shows an increase in formation of organic nitrate (RONO2) from the downstream RO2+NO reaction, which is attributed to potential collisional and solvent-cage stabilization of the RO2–NO complex. We further observe an enhancement in the yield of carbonyl relative to hydroxy carbonyl products in the condensed phase, indicating changes to RO radical kinetics. The different branching ratios in the condensed phase impact the product volatility distribution as well as HOx-NOx chemistry, and may have implications for nitrate formation, aqueous aerosol formation, and radical cycling within atmospheric particles and droplets.

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1. Introduction

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The oxidation of organic species in the atmospheric condensed phase (aerosol particles and droplets) is a key chemical process with important implications for atmospheric composition. Multiphase oxidation alters the chemical composition and properties (hygroscopicity, optical properties, etc.) of particles, affects gas phase composition, (1) and can lead to the formation of secondary organic aerosol via reactions in cloud and aerosol water (aqueous organic aerosol (aqSOA)). (2−4) Such chemistry is thought to proceed via the same general mechanism as oxidation in the gas phase, in which the organic compound is attacked by an oxidant (e.g., the hydroxyl radical OH), leading to a sequence of reactions involving alkoxy (RO) and peroxy (RO2) radicals, and ultimately forming closed-shell organic products. (5−8) However, radical chemistry in the condensed phase is substantially more complicated than in the gas phase due to the presence of the solvent, which can affect radical reactivity via effects such as collisional stabilization, direct involvement of solvent molecules, and changes to reaction thermodynamics and kinetics due to solvent–solute interactions. (9−11) These effects may lead to product distributions that are fundamentally different from those in the gas phase, and so may impact the composition of both the gas and particle phases.
Much of our understanding of condensed-phase organic radical chemistry is based on off-line studies of liquid-phase oxidation reactions, such as pulsed radiolysis measurements of the reaction of OH radicals with organic species in the aqueous phase (12−14) and on a limited number of online studies of liquid-phase oxidation. (15) A difficulty in interpreting results from such studies is the substantial chemical complexity associated with organic oxidation processes, particularly for large molecules: a single reaction step can form different organic radicals, high oxidant levels can lead to multiple generations of oxidation, and products can have multiple functional groups, posing analytical challenges.
Here we take an alternative approach for studying the condensed-phase chemistry of organic radicals, involving radical generation via direct photolysis. In particular, we explore the multiphase chemistry of a single organic radical, 1-pentoxy (C5H9O), generated from photolysis of a n-pentyl nitrite (PN) precursor:
CH3(CH2)4ONO+hν→CH3(CH2)4O+NO
(R1)
Direct radical generation allows for the formation of a single radical isomer, which in comparison to traditional oxidant-initiated oxidation affords substantially simpler chemistry, and largely avoids unwanted secondary oxidation reactions. (16,17) We employ this approach in three different systems: the gas phase, the bulk organic condensed phase, and the bulk aqueous phase. Online detection of product species allows for the direct comparison of the chemistry of the 1-pentoxy radical (and its downstream intermediates, including RO2 radicals) among these three phases.

2. Methods and Materials

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Different reactor setups are used to probe radical chemistry in different phases (see Figure S5). Condensed-phase experiments are conducted in a 10 mL borosilicate volumetric flask equipped with a magnetic stir bar. Hexafluorobenzene (C6F6, Sigma-Aldrich, NMR grade, > 99.5%), a nonpolar, aprotic molecule, is used as the solvent for the organic phase experiments. For aqueous experiments, 0.05 M, pH 7 phosphate buffer is used as the solvent to minimize the effects of RONO hydrolysis (see SI). (18) 0.125 μL of acetonitrile (Sigma-Aldrich, 99.8%) is added to each solution as a flow tracer (5.0 ppmv). 6.25 μL of PN (Sigma-Aldrich, > 95%) is then added to each solution (250 ppmv). The solution is continually mixed using a stir bar, ensuring that organics are homogeneously distributed in the bulk solution prior to and during photolysis; this also avoids depletion of O2 within the solution. The solution is then photolyzed using a strip of UVA LEDs (λ = 365 nm, Waveform Lighting). Consistent with the product distributions (discussed below), the high concentration of RONO used in the experiments results in conditions in which the reactivity of RO2 radicals is dominated by RO2 + NO chemistry, with negligible contribution from other RO2 reactions. The solution is introduced into an atomizer (Brechtel Manufacturing) using a peristaltic pump (ESI MP2) at a flow rate of 12 μL/min. The solution is converted to a fine spray which rapidly vaporizes as it is diluted with ∼20 LPM of clean, dry air; analysis with a scanning mobility particle sizer (SMPS, TSI) shows no evidence of aerosol particles, indicating full vaporization. The diluted, vaporized effluent is sampled into the NH4+ CIMS for detection (see SI, including Figure S5). Several control experiments (see SI) indicate that tubing losses may contribute to a slight change in shape of the time traces, but this leads to negligible changes in product distributions. While the experiments are designed to probe bulk-phase chemistry, and observations are consistent with such chemistry, surface or bulk droplet-phase chemistry in the atomizer cannot be completely ruled out. Future experiments relying on liquid-phase analytical techniques could clarify the results further.
Gas-phase experiments are conducted in the MIT environmental chamber. (19) During experiments, a constant 5 LPM flow of zero air from a clean air generator (Aadco 737 Series) is introduced into the chamber to replenish the flow drawn by the instruments. To mimic the high NO concentrations accessed in the condensed-phase experiments, ∼ 200 ppb of NO, monitored by a chemiluminescence NO−NO2–NOx analyzer (Thermo Scientific, Model 42i), are added. As in the condensed-phase experiments, observed products suggest that RO2 reacts only with NO under these conditions; when no NO is added, the dominant products observed are consistent with RO2 + HO2 reactions (see SI). Acetonitrile is injected into the chamber as a dilution tracer. 45 ppb of the PN radical precursor are then injected into the chamber. The concentrations are allowed to stabilize for approximately 10 min, and then the UV-A lamps (centered at 340 nm) are switched on to initiate photolysis.
Reaction products generated in both setups are measured in real time using a time-of-flight NH4+ CIMS, (20) which is sensitive to a wide range of oxygenated VOCs. Given the uncertainty associated with calibration of the NH4+ CIMS, in this work we report CIMS measurements in terms of mass spectrometric signal (duty-cycle-corrected counts per second), normalized to the acetonitrile signal to correct for variations in flow. Because the CIMS sensitivity may vary from compound to compound, these values may not accurately reflect relative concentrations of the different species. We thus restrict our discussion to differences in concentrations between phases. The three experiments are performed using the same instrument under similar operating conditions; calibration factors for a given compound are the same and so signal intensities are directly comparable between experiments.

3. Results and Discussion

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Stacked plots depicting the time evolution of photochemical product ions observed in the three experiments (gas phase, organic condensed phase, and aqueous phase) are presented in Figure 1. Molecular formulas are detected as the analyte-NH4+ adduct unless otherwise noted, but are presented as the molecular formula of the analyte (omitting the NH4+). In all cases, products are consistent with the expected chemistry of the 1-pentoxy radical under RO2 + NO conditions, (21,22) shown in Figure 2. No evidence of second-generation oxidation chemistry (e.g., due to OH formed from HO2 + NO) is observed. The proposed mechanism accounts for all observed major products, though the presence of alternative pathways or minor products cannot be fully ruled out. The 1-pentoxy radical, formed from RONO photolysis, forms either a carbonyl (C5H10O) through reaction with O2 or a hydroxyperoxy (RO2) radical via isomerization. Under the conditions of these experiments, the RO2 reacts with NO; this is thought to form a peroxynitrite intermediate, which either rearranges to form the hydroxy nitrate (C5H11NO4) or dissociates to yield another RO radical, ultimately producing a hydroxycarbonyl (C5H10O2). As both of these products are the result of the reaction between RO2 and NO, the branching ratio between the two pathways is independent of NO concentration. Also observed in the gas-phase experiment is a species with formula C5H8O, consistent with the dehydration of the hydroxycarbonyl (see SI). One additional product, C5H12O, is observed in the aqueous phase only, and is likely the alcohol formed from the hydrolysis of the RONO precursor (see SI). (18)

Figure 1

Figure 1. : Time-resolved mass spectrometric signals for n-pentyl nitrite photolysis products, in three phases: (a) the gas phase, (b) the condensed organic phase, and (3) the aqueous phase. All measurements use the NH4+ CIMS, and formulas listed are those of the analytes (products are detected as the complexes with NH4+). Signals are smoothed over 15-s intervals and normalized to the dilution tracer, acetonitrile; t = 0 refers to the time at which UV lights are switched on.

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Figure 2

Figure 2. : Simplified reaction mechanism for the photolysis of n-pentyl nitrite. Detected closed-shell products are highlighted, with colors corresponding to the products shown in Figure 1.

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Substantial differences in product distributions are observed between the experiments in different phases, with the most pronounced differences being between the gas phase and the two condensed phases. This implies differences in rates and branching ratios among phases, which we quantified by fitting time-dependent product signals to a kinetic model (see SI). Key rate constants and branching ratios are given in Table 1. As discussed further in SI, the alkoxy radical branching ratio and the nitrate yield given in Table 1 are derived from uncalibrated CIMS measurements, and hence may contain as much as a factor of 2–3 absolute error for individual values based on differing sensitivities for different products. However, calibration factors are likely to be the same in different phases, so uncertainties cancel out for the ratios reported in Table 2.
Table 1. : Model Fitted Parameters for the Gas, Organic, and Aqueous Phase Photolysis of n-Pentyl Nitrite
 Photolysis rate constantHydrolysis rate constantAlkoxy radical branching ratioNitrate branching ratio from RO2 + NO
Phasej1 (s–1)k8 (s–1)k3[O2]/(k3[O2] + k2)X5a
Gas(2.9 ± 0.1) × 10–4N/A(6.6 ± 0.4) × 10–30.22 ± 0.001
Organic(4.3 ± 0.6) × 10–3N/A0.099 ± 0.0080.86 ± 0.04
Aqueous(7.0 ± 0.2) × 10–5(1.6 ± 0.7) × 10–30.31 ± 0.0070.79 ± 0.03
Table 2. Literature Values for X5a in the Gas and Aqueous Phases, and Enhancement Factor (Ratio of X5a Values) between the Two Phases
Peroxy RadicalX5a(g), 1 atm, 298 KX5a(aq), 298 KX5a(aq)/X5a(g)
Methyl Peroxy0.017 ± 0.0014 (25)0.23 ± 0.4 (24) 0.86 ± 0.02 (28)14, 51
Ethyl Peroxy0.033 ± 0.004 (29)0.67 ± 0.03 (24)20
Propyl Peroxy0.038 ± 0.002 (30),a 0.036 ± 0.005 (31),b0.71 ± 0.04 (24),b19
Tert-Butanol Peroxy0.044 (23)0.86 ± 0.02 (28)20
5-hydroxy-pentan-2-yl peroxy0.13 (23)0.24 (23)1.8 (23) 3.5c
a

All values are taken from measurements, apart from italicized items which are calculated from the structure–activity relationship presented by Jenkin et al. (23) Reported value for isopropyl peroxy radical only.

b

Reported value for a combination of n-propyl and isopropyl peroxy radicals.

c

This work.

The most obvious difference in product distribution in the different phases is the organic nitrate (C5H11NO4): this is a minor product in the gas-phase system (Figure 1a), as expected, (23) but is one of the most abundant products in the two condensed-phase systems (Figure 1b-c). This indicates a substantial difference in RO2 + NO branching (R5) in different phases: as shown in Table 1, values of X5a are a factor of 4 and 3.5 larger in the organic condensed phase and aqueous phase, respectively, than in the gas phase. To our knowledge, this enhanced nitrate formation has not previously been examined in the context of the atmospheric condensed phase (aerosol particles and droplets). However, earlier work examining RO2 chemistry in other aqueous systems (e.g., seawater) has found similar enhancements in the RONO2 yields from the RO2 + NO reaction in the aqueous phase for a number of small RO2 radicals. (24,25) Literature values for gas- and aqueous-phase RONO2 branching ratios, as well as the enhancement factor in the aqueous phase (X5a(aq)/X5a(g)) are summarized in Table 2. Interestingly, the enhancement factor observed in this study is substantially lower than those observed for small, unsubstituted RO2. One possible origin of this difference is the molecular structure of the RO2 radical itself; future studies exploring the influence of RO2 structure on the aqueous phase enhancement factor would provide further insight into this effect. By contrast, two previous studies on heterogeneous oxidation of liquid organic particles in the presence of gas-phase NO (26,27) observed no alkyl nitrate formation; this inconsistency may arise differences in experimental conditions (e.g., oxidation from the gas phase rather that from within the condensed phase) and/or analytical approaches used.
The difference between gas- and condensed-phase RONO2 branching ratios likely arises from differences in the dynamics of the ROONO intermediate, which can either rearrange to form RONO2 or dissociate to RO + NO2 (Figure 2). (32) The enhancement in RONO2 yield in the condensed phase is consistent with the well-established increase in RONO2 yields with pressure, which is likely due to collisional stabilization of the ROONO intermediate. (31−33) From the number concentration of water molecules, we can estimate an enhancement of X5a in the aqueous phase using known pressure-dependences. We predict an enhancement of 1.8, qualitatively consistent with (but lower than) the enhancement of 3.5 observed in this experiment.
Another possible contributing factor is the solvent cage effect, which keeps the reactive fragment species (RO and NO2) in close proximity, thereby increasing the potential for collisions and consequently the probability of recombination. (34) Previous work on a similar molecule, peroxynitrous acid (HOONO), has suggested that such an effect could play a role in preventing the decomposition to OH + NO2 (analogous to the decomposition of ROONO to RO + NO2). (35) Additional experimental and computational work is needed to better understand the roles of both collisional stabilization and the solvent cage effects on the phase-dependent RONO2 yields.
The other major difference between the gas- and condensed-phase product distributions is the enhanced yield of the carbonyl species (C5H10O) in the condensed phase. This suggests a difference in the chemistry of the RO radical. In particular, the relative rate of reaction with O2 and isomerization (i.e., k3[O2]/k2) is enhanced by a factor of ∼16 for the condensed organic phase compared to the gas phase, an enhancement that increases to ∼69 for the aqueous phase (Table 1). The difference is not a result of differences in O2 concentrations: from Henry’s Law constants, (36) the O2 concentrations in H2O and C6F6 are a factor of 31 and a factor of 2 lower than in the gas phase, respectively, which should result in a decreased condensed-phase yield, contrary to observation.
There are a number of possible processes which may contribute to the observed differences, including chemically activated reactions of the nascent, internally excited RO radical, (37) changes in the barriers to reactions R2 and R3 due to solvation, and the possibility of additional chemistry in the condensed phase (e.g., an 1,2 H atom shift, which has been previously observed for some RO radicals in protic solvents (38−44)). Future work, including theoretical calculations, are necessary to better understand the origin of the observed change, and evaluate the extent to which this observation is generalizable to other RO systems.

4. Conclusions and Atmospheric Relevance

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In this study, we have demonstrated the parallel analysis of gas- and condensed-phase products of RO and RO2 radicals using a consistent methodology, allowing for direct comparisons of branching ratios across phases. The most striking difference is the enhancement in nitrate formation in the condensed phase. This enhancement has been previously reported in smaller peroxy radicals (C1–C4) in seawater. (24) Here, we present, to our knowledge, the first observation of this effect for a large and/or functionalized RO2. Interestingly, the enhancement in X5a observed in this work in the aqueous phase is considerably smaller than in other smaller RO2 systems (Table 2), suggesting that size and/or functionality influences the RO2 fate. This discrepancy also points to the need for further investigation of other large RO/RO2 radicals, both through experiments and computational investigations.
The enhancement of nitrate yield from larger RO2 may have an effect on the composition of atmospheric aerosols or droplets, and in particular on the composition of aqSOA. Moreover, since organic nitrates can serve as reservoir species for NOx, this RONO2 enhancement could have implications for the NOx budget, affecting NOx partitioning and hence ozone formation and radical cycling. Related to this, increased nitrate formation–as well as the enhanced carbonyl yield observed–result in an enhancement in chain termination steps in both condensed phases (this remains true even if the condensed-phase nitrate undergoes hydrolysis, forming an alcohol and HNO3). This suggests that oxidation of organic species in the atmospheric condensed phase results in the formation of less-oxidized products than in the gas phase, and would require more oxidation steps (initiated by additional oxidants or UV light) to form highly oxidized products.
The degree to which these changes in condensed-phase product yields impact the chemistry of the atmosphere depends critically on the levels of NO in aqueous droplets and organic aerosol particles, since NO concentrations govern the rate of formation of RO radicals as well as RO2 fate. Given the low Henry’s Law solubility of NO, (45) partitioning of NO from the gas phase likely contributes negligibly to concentrations in the atmospheric condensed phase. However, NO can also be formed in situ from condensed-phase photolysis of inorganic nitrate and nitrite; (28,46) further study of these reactions, as well as the time scale of equilibration of solution-phase concentrations of NO, is important to quantitatively estimate condensed-phase NO concentrations in the atmosphere, and to understand the potential importance of condensed-phase RO2 + NO reactions.
In addition, the underlying physical-chemical explanations for the observed dependence of branching ratios on phase remain uncertain. Computational study of the chemistry of RO and RO2 radicals in both the gas phase and various condensed phases could provide important insight into these observations. Furthermore, chemical structure (carbon skeleton and functional groups) are known to have a governing influence on RO and RO2 branching ratios, (22,23,47) and so other species may exhibit substantially different branching ratio enhancements in the condensed phase. The chemical environment is also likely to play a role, and future work on the impact of radical-solvent interactions (e.g., proton-exchange chemistry) and the presence of other radical and oxidant species would further clarify the importance of the observed effects in real atmospheric systems. Finally, chemistry within particles and droplets can be fundamentally different from that in bulk condensed-phase environments, due to differences in pH, mass transfer limitations, and surface effects; however it is unknown to what extent these effects will impact RO and RO2 branching ratios. Detailed experimental and computational investigations of condensed-phase radicals are necessary to extend these results to the full range of organic compounds and condensed-phase environments found in the atmosphere.

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.estlett.4c00473.

  • Additional details on experimental methods, including a diagram of the experimental setup; additional results, including an analysis of the pH dependence of n-pentyl nitrite hydrolysis, an analysis of tubing effects on the observed kinetics, and results of low-NO gas-phase experiments; a detailed derivation of the kinetic model used for extracting rate constants and branching ratios; a comparison between modeled and measured time profiles (PDF)

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Author Information

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  • Corresponding Authors
    • Victoria P. Barber - Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States;  Present Address: V.P.B.: Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095, United States;  Orcidhttps://orcid.org/0000-0003-4543-4657;  Email: [email protected]
    • Jesse H. Kroll - Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States;  Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States;  Orcidhttps://orcid.org/0000-0002-6275-521X;  Email: [email protected]
  • Authors
    • Lexy N. LeMar - Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
    • Yaowei Li - John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States;  Orcidhttps://orcid.org/0000-0003-0725-6108
    • Jonathan W. Zheng - Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
    • Frank N. Keutsch - John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States;  Orcidhttps://orcid.org/0000-0002-1442-6200
  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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This work is supported by NSF grant CHE-210881. The authors gratefully acknowledge William H. Green (MIT), and Hartmut Herrmann and Erik H. Hoffmann (Leibniz-Institute for Tropospheric Research) for helpful discussions.

References

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This article references 47 other publications.

  1. 1
    Hoffmann, E. H.; Tilgner, A.; Schrödner, R.; Bräuer, P.; Wolke, R.; Herrmann, H. An Advanced Modeling Study on the Impacts and Atmospheric Implications of Multiphase Dimethyl Sulfide Chemistry. Proc. Natl. Acad. Sci. U. S. A. 2016, 113 (42), 11776– 11781,  DOI: 10.1073/pnas.1606320113
    Google Scholar
    1
    An advanced modeling study on the impacts and atmospheric implications of multiphase dimethyl sulfide chemistry
    Hoffmann, Erik Hans; Tilgner, Andreas; Schroedner, Roland; Braeuer, Peter; Wolke, Ralf; Herrmann, Hartmut
    Proceedings of the National Academy of Sciences of the United States of America (2016), 113 (42), 11776-11781CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
    Oceans dominate di-Me sulfide (DMS) emissions, the major natural S source. DMS is important for formation of non-sea salt sulfate (nss-SO42-) aerosols and secondary particulate matter over oceans; thus, it significantly affects global climate. The DMS oxidn. mechanism has been examd. in several different model studies; however, these studies had restricted oxidn. mechanisms which mainly under-represented important aq.-phase chem. processes. These neglected but highly effective processes strongly affect the direct product yields of DMS oxidn., thereby affecting the climatic influence of aerosols. To address these shortfalls, an extensive multiphase DMS chem. mechanism, the Chem. Aq. Phase Radical Mechanism DMS Module 1.0, was developed and used in detailed model assessments of multiphase DMS chem. in the marine boundary layer. Model studies confirmed the importance of aq. phase chem. for the fate of DMS and its oxidn. products. Aq. phase processes significantly reduced the SO2 yield and increased the Me sulfonic acid (MSA) yield, which is needed to close the gap between modeled and measured MSA concns. Simulations implied that multi-phase DMS oxidn. produces equal amts. of MSA and SO42-, a result with significant implications for nss-SO42- aerosol formation, cloud condensation nuclei concn., and cloud albedo over oceans. Results showed the deficiencies of parameterizations currently used in higher-scale models which only treat gas phase chem. Overall, the results showed treatment of DMS chem. in gas and aq. phases is essential to improve model prediction accuracy.
  2. 2
    George, I. J.; Abbatt, J. P. D. Heterogeneous Oxidation of Atmospheric Aerosol Particles by Gas-Phase Radicals. Nat. Chem. 2010, 2 (9), 713– 722,  DOI: 10.1038/nchem.806
    Google Scholar
    2
    Heterogeneous oxidation of atmospheric aerosol particles by gas-phase radicals
    George, I. J.; Abbatt, J. P. D.
    Nature Chemistry (2010), 2 (9), 713-722CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)
    A review concerning the heterogeneous oxidn. of org. and inorg. constituents of atm. aerosols by gas-phase radicals is given, focusing on the kinetics and reaction mechanisms and how they affect particle physicochem. properties (compn., size, d., hygroscopicity). Potential atm. impacts include: release of chem. reactive gases, e.g., halogens, aldehydes and org. acids; reactive loss of particle-borne mol. tracer and toxic species; and enhanced hygroscopic properties of aerosols which may improve their ability to form cloud droplets. Topics discussed include: radical uptake on atm. relevant surfaces; oxidn. of condensed-phase org. and inorg. compds.; particle physicochem. property modification; atm. implications; and outlook.
  3. 3
    Lambe, A. T.; Cappa, C. D.; Massoli, P.; Onasch, T. B.; Forestieri, S. D.; Martin, A. T.; Cummings, M. J.; Croasdale, D. R.; Brune, W. H.; Worsnop, D. R.; Davidovits, P. Relationship between Oxidation Level and Optical Properties of Secondary Organic Aerosol. Environ. Sci. Technol. 2013, 47 (12), 6349– 6357,  DOI: 10.1021/es401043j
    Google Scholar
    3
    Relationship between Oxidation Level and Optical Properties of Secondary Organic Aerosol
    Lambe, Andrew T.; Cappa, Christopher D.; Massoli, Paola; Onasch, Timothy B.; Forestieri, Sara D.; Martin, Alexander T.; Cummings, Molly J.; Croasdale, David R.; Brune, William H.; Worsnop, Douglas R.; Davidovits, Paul
    Environmental Science & Technology (2013), 47 (12), 6349-6357CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    Brown carbon (BrC), which may include secondary org. aerosol (SOA), can be a significant climate-forcing agent through its optical absorption properties; however, the overall contribution of SOA to BrC remains poorly understood. This work examd. correlations between oxidn. level and SOA optical properties. SOA was generated in a flow reactor in the absence of NOx by OH- oxidn. of gaseous precursors as surrogates for anthropogenic (naphthalene, tricyclo[5.2.1.02,6]decane), biomass burning (guaiacol), and biogenic (α-pinene) emissions. SOA chem. compn. was characterized by time-of-flight aerosol mass spectrometry. SOA mass-specific absorption cross sections (MAC) and refractive indexes were calcd. from real-time cavity ring-down photo-acoustic spectrometry measurements at 405 and 532 nm and from UV-vis spectrometry measurements of methanol exts. of filter-collected particles (300-600 nm). At 405 nm, SOA MAC values and imaginary refractive indexes increased with increasing oxidn. level and decreased with increasing wavelength, leading to negligible absorption at 532 nm. SOA real refractive indexes decreased with increasing oxidn. level. A literature study comparison suggested that under typical polluted conditions, the effect of NOx on SOA absorption was small. SOA may significantly contribute to atm. BrC; the magnitude depends on precursor type and oxidn. level.
  4. 4
    Galeazzo, T.; Valorso, R.; Li, Y.; Camredon, M.; Aumont, B.; Shiraiwa, M. Estimation of Secondary Organic Aerosol Viscosity from Explicit Modeling of Gas-Phase Oxidation of Isoprene and α-Pinene. Atmospheric Chem. Phys. 2021, 21 (13), 10199– 10213,  DOI: 10.5194/acp-21-10199-2021
    Google Scholar
    4
    Estimation of secondary organic aerosol viscosity from explicit modeling of gas-phase oxidation of isoprene and α-pinene
    Galeazzo, Tommaso; Valorso, Richard; Li, Ying; Camredon, Marie; Aumont, Bernard; Shiraiwa, Manabu
    Atmospheric Chemistry and Physics (2021), 21 (13), 10199-10213CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
    Secondary org. aerosols (SOA) are major components of atm. fine particulate matter, affecting climate and air quality. Mounting evidence exists that SOA can adopt glassy and viscous semisolid states, impacting formation and partitioning of SOA. In this study, we apply the GECKO-A (Generator of Explicit Chem. and Kinetics of Orgs. in the Atm.) model to conduct explicit chem. modeling of isoprene photooxidn. and α-pinene ozonolysis and their subsequent SOA formation. The detailed gas-phase chem. schemes from GECKO-A are implemented into a box model and coupled to our recently developed glass transition temp. parameterizations, allowing us to predict SOA viscosity. The effects of chem. compn., relative humidity, mass loadings and mass accommodation on particle viscosity are investigated in comparison with measurements of SOA viscosity. The simulated viscosity of isoprene SOA agrees well with viscosity measurements as a function of relative humidity, while the model underestimates viscosity of α-pinene SOA by a few orders of magnitude. This difference may be due to missing processes in the model, including autoxidn. and particle-phase reactions, leading to the formation of high-molar-mass compds. that would increase particle viscosity. Addnl. simulations imply that kinetic limitations of bulk diffusion and redn. in mass accommodation coeff. may play a role in enhancing particle viscosity by suppressing condensation of semi-volatile compds. The developed model is a useful tool for anal. and investigation of the interplay among gas-phase reactions, particle chem. compn. and SOA phase state.
  5. 5
    Kroll, J. H.; Seinfeld, J. H. Chemistry of Secondary Organic Aerosol: Formation and Evolution of Low-Volatility Organics in the Atmosphere. Atmos. Environ. 2008, 42 (16), 3593– 3624,  DOI: 10.1016/j.atmosenv.2008.01.003
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    5
    Chemistry of secondary organic aerosol: Formation and evolution of low-volatility organics in the atmosphere
    Kroll, Jesse H.; Seinfeld, John H.
    Atmospheric Environment (2008), 42 (16), 3593-3624CODEN: AENVEQ; ISSN:1352-2310. (Elsevier Ltd.)
    A review is given. Secondary org. aerosol (SOA), particulate matter composed of compds. formed from the atm. transformation of org. species, accounts for a substantial fraction of tropospheric aerosol. The formation of low-volatility (semivolatile and possibly nonvolatile) compds. that make up SOA is governed by a complex series of reactions of a large no. of org. species, so the exptl. characterization and theor. description of SOA formation presents a substantial challenge. We outline what is known about the chem. of formation and continuing transformation of low-volatility species in the atm. The primary focus is chem. processes that can change the volatility of org. compds.: (1) oxidn. reactions in the gas phase, (2) reactions in the particle phase, and (3) continuing chem. (in either phase) over several generations. Gas-phase oxidn. reactions can reduce volatility by the addn. of polar functional groups or increase it by the cleavage of carbon-carbon bonds; key branch points that control volatility are the initial attack of the oxidant, reactions of alkylperoxy (RO2) radicals, and reactions of alkoxy (RO) radicals. Reactions in the particle phase include oxidn. reactions as well as accretion reactions, non-oxidative processes leading to the formation of high-mol.-wt. species. Org. C in the atm. is continually subject to reactions in the gas and particle phases throughout its atm. lifetime (until lost by phys. deposition or oxidized to CO or CO2), implying continual changes in volatility over the timescales of several days. The volatility changes arising from these chem. reactions must be parameterized and included in models in order to gain a quant. and predictive understanding of SOA formation.
  6. 6
    Calvert, J. G.; Derwent, R. G.; Orlando, J. J.; Wallington, T. J.; Tyndall, G. S. Mechanisms of Atmospheric Oxidation of the Alkanes; Oxford University Press: Oxford, NY, 2008.
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    There is no corresponding record for this reference.
  7. 7
    Atkinson, R.; Arey, J. Atmospheric Degradation of Volatile Organic Compounds. Chem. Rev. 2003, 103 (12), 4605– 4638,  DOI: 10.1021/cr0206420
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    7
    Atmospheric Degradation of Volatile Organic Compounds
    Atkinson, Roger; Arey, Janet
    Chemical Reviews (Washington, DC, United States) (2003), 103 (12), 4605-4638CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review concerning the removal of biogenic and anthropogenic volatile org. compds. (VOC) emitted to the atm. through phys. (deposition) or chem. processes, or their atm. transformation is given. Topics discussed include: tropospheric VOC transformation processes (initial reactions and lifetimes, reaction mechanisms); atm. chem. of alkanes (kinetic data for initial OH- and NO3- reactions, reaction mechanism); atm. chem. of alkenes (rate consts. for initial reaction of alkenes with OH-, NO3-, and O3; mechanism of the OH- reaction; NO3- reaction; reaction with O3); arom. hydrocarbons (kinetics of OH- reactions, reactions of phenols, reactions of unsatd. 1,4-dicarbonyls and di-unsatd. 1,6-dicarbonyls); atm. reactions of oxygenated VOC (aldehydes, ketones, aliph. alcs., ethers, alkyl nitrates); and conclusions and future research needs (exptl. studies, theor. studies and crit. reviews and evaluations).
  8. 8
    Calvert, J. G.; Mellouki, A.; Orlando, J. J. Mechanisms of Atmospheric Oxidation of the Oxygenates; Oxford University Press: Oxford, NY, 2011. DOI: 10.1093/oso/9780195365818.005.0001 .
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    There is no corresponding record for this reference.
  9. 9
    Leviss, D. H.; Van Ry, D. A.; Hinrichs, R. Z. Multiphase Ozonolysis of Aqueous α-Terpineol. Environ. Sci. Technol. 2016, 50 (21), 11698– 11705,  DOI: 10.1021/acs.est.6b03612
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    9
    Multiphase Ozonolysis of Aqueous α-Terpineol
    Leviss, Dani H.; Van Ry, Daryl A.; Hinrichs, Ryan Z.
    Environmental Science & Technology (2016), 50 (21), 11698-11705CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    Multiphase ozonolysis of aq. orgs. presents a potential pathway for the formation of aq. secondary org. aerosol (aqSOA). We investigated the multiphase ozonolysis of α-terpineol, an oxygenated deriv. of limonene, and found that the reaction products and kinetics differ from the gas-phase ozonolysis of α-terpineol. One- and two-dimensional NMR spectroscopies along with GC-MS identified the aq. ozonolysis reaction products as trans- and cis-lactols [4-(5-hydroxy-2,2-dimethyltetrahydrofuran-3-yl)butan-2-one] and a lactone [4-hydroxy-4-methyl-3-(3-oxobutyl)-valeric acid gamma-lactone], which accounted for 46%, 27%, and 20% of the obsd. products, resp. Hydrogen peroxide was also formed in 10% yield consistent with a mechanism involving decompn. of hydroxyl hydroperoxide intermediates followed by hemiacetal ring closure. Multiphase reaction kinetics at gaseous ozone concns. of 131, 480, and 965 parts-per-billion were analyzed using a resistance model of net ozone uptake and found the second-order rate coeff. for the aq. reaction of α-terpineol + O3 to be 9.9(±3.3) × 106 M-1 s-1. Multiphase ozonolysis will therefore be competitive with multiphase oxidn. by hydroxyl radicals (OH) and ozonolysis of gaseous α-terpineol. We also measured product yields for the heterogeneous ozonolysis of α-terpineol adsorbed on glass, NaCl, and kaolinite, and identified the same three major products but with an increasing lactone yield of 33, 49, and 55% on these substrates, resp.
  10. 10
    Akimoto, H.; Hirokawa, J. Atmospheric Multiphase Chemistry: Fundamentals of Secondary Aerosol Formation; John Wiley & Sons, 2020. DOI: 10.1002/9781119422419 .
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    There is no corresponding record for this reference.
  11. 11
    Thornberry, T.; Abbatt, J. P. D. Heterogeneous Reaction of Ozone with Liquid Unsaturated Fatty Acids: Detailed Kinetics and Gas-Phase Product Studies. Phys. Chem. Chem. Phys. 2004, 6 (1), 84– 93,  DOI: 10.1039/b310149e
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    11
    Heterogeneous reaction of ozone with liquid unsaturated fatty acids: detailed kinetics and gas-phase product studies
    Thornberry, T.; Abbatt, J. P. D.
    Physical Chemistry Chemical Physics (2004), 6 (1), 84-93CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    Detailed kinetic and product yield studies have been performed for the heterogeneous reaction between gas-phase ozone and three liq. fatty acids using a coated-wall flow tube and chem. ionization mass spectrometry. Gas-surface reaction probabilities for ozone loss of (8.0 ±1.0) × 10-4, (1.3 ±0.1) × 10-3, and (1.8 ±0.2) × 10-3 have been measured at room temp. (298 K) for oleic acid, linoleic acid, and linolenic acid, resp. The temp. dependence of the uptake coeffs. was found to be small and pos. Comparison of these results to the kinetics of the equiv. gas-phase reactions implies that there is a definite enhancement in the rate for the heterogeneous process due to entropic factors, i.e., due to collisional trapping of ozone in the surface layers of the liq., and a possible effect on the activation energy of the reaction. For linoleic acid, the reaction probability was found to be independent of relative humidity (up to 55%), to ±10%, at 263 K. Volatile reaction products were obsd. using proton-transfer-reaction mass spectrometry. Nonanal was obsd. with a 0.50 (±0.10) yield for the reaction with oleic acid, whereas hexanal and nonenal were obsd. for linoleic acid with 0.25 (±0.05) and 0.29 (±0.05) yields, resp. These results indicate that the primary ozonide formed initially in the reaction can decomp. via two equal probability pathways and that a secondary ozonide is not formed in high yield in the aldehydic channel. These reactions represent a source of oxygenates to the atm. and will modify the hygroscopic properties of aerosols.
  12. 12
    Adams, G. E.; Willson, R. L. Pulse Radiolysis Studies on the Oxidation of Organic Radicals in Aqueous Solution. Trans. Faraday Soc. 1969, 65, 2981,  DOI: 10.1039/tf9696502981
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    12
    Pulse radiolysis studies on the oxidation of organic radicals in aqueous solution
    Adams, Gerald Edward; Willson, Robin Lindhope
    Transactions of the Faraday Society (1969), 65 (11), 2981-7CODEN: TFSOA4; ISSN:0014-7672.
    Pulse radiolysis has been used to measure directly the abs. rates of oxidn. by ferricyanide ion of various radicals produced by OH attack on org. solutes. These include mono-, di-, and polyhydroxylic compds., hydroxy acids, polyethylene oxides of mol. wt. 200, 6000, and 20,000 and the amino acid serine. Radicals produced by H abstraction from α-C atoms in alcs. are oxidized at, or near, diffusion-controlled rates, whereas the reactions are much slower for radicals formed by OH-attack elsewhere. The technique has been used to measure the percentage of OH attack at the α-position for a series of straight and branched-chain alcs. O competes with ferricyanide for radical oxidn. The data for O-contg. solns. fit a simple radical-competition scheme which has been used to measure rates of peroxy-radical formation. These approach diffusion-controlled limits.
  13. 13
    Schuchmann, M. N.; Von Sonntag, C. The Rapid Hydration of the Acetyl Radical. A Pulse Radiolysis Study of Acetaldehyde in Aqueous Solution. J. Am. Chem. Soc. 1988, 110 (17), 5698– 5701,  DOI: 10.1021/ja00225a019
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    13
    The rapid hydration of the acetyl radical. A pulse radiolysis study of acetaldehyde in aqueous solution.
    Schuchmann, Man Nien; Von Sonntag, Clemens
    Journal of the American Chemical Society (1988), 110 (17), 5698-701CODEN: JACSAT; ISSN:0002-7863.
    In aq. soln. acetaldehyde and its hydrate are in a 0.8:1 equil. Hydroxyl radicals, generated by the pulse radiolysis of N2O-satd. water, react with acetaldehyde about 3 times faster than with the hydrate. The predominant radicals formed are the acetyl radical and its hydrated form, H-abstraction at Me occurring to only about 5-10%. The acetyl radical rapidly hydrates. Its rate of hydration is 2 × 106 times faster than that of acetaldehyde. The hydrated acetyl radical has been monitored by its rapid redn. of tetranitromethane, the formation of O2- in the presence of Oxygen, and its deprotonation at pH 11. The acetyl radical does not oxidize N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) on the pulse radiolysis time scale. The acetylperoxyl radical (formed in the presence of oxygen) reacts rapidly with TMPD, ascorbate, and O2-; it is the most strongly oxidizing peroxyl radical known so far. Data on the rate of water loss from the hydrated acetyl radical are considerably less accurate, but the rate const. in estd.
  14. 14
    Mezyk, S. P.; Elliot, A. J. Pulse Radiolysis of Iodate in Aqueous Solution. J. Chem. Soc. Faraday Trans. 1994, 90 (6), 831– 836,  DOI: 10.1039/ft9949000831
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    There is no corresponding record for this reference.
  15. 15
    Lee, A. K. Y.; Zhao, R.; Gao, S. S.; Abbatt, J. P. D. Aqueous-Phase OH Oxidation of Glyoxal: Application of a Novel Analytical Approach Employing Aerosol Mass Spectrometry and Complementary Off-Line Techniques. J. Phys. Chem. A 2011, 115 (38), 10517– 10526,  DOI: 10.1021/jp204099g
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    15
    Aqueous-phase OH oxidation of glyoxal: application of a novel analytical approach employing aerosol mass spectrometry and complementary off-line techniques
    Lee, Alex K. Y.; Zhao, R.; Gao, S. S.; Abbatt, J. P. D.
    Journal of Physical Chemistry A (2011), 115 (38), 10517-10526CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
    Aq.-phase chem. of glyoxal may play an important role in the formation of highly oxidized secondary org. aerosol (SOA) in the atm. In this work, we use a novel design of photochem. reactor that allows for simultaneous photo-oxidn. and atomization of a bulk soln. to study the aq.-phase OH oxidn. of glyoxal. By employing both online aerosol mass spectrometry (AMS) and offline ion chromatog. (IC) measurements, glyoxal and some major products including formic acid, glyoxylic acid, and oxalic acid in the reacting soln. were simultaneously quantified. This is the first attempt to use AMS in kinetics studies of this type. The results illustrate the formation of highly oxidized products that likely coexist with traditional SOA materials, thus, potentially improving model predictions of org. aerosol mass loading and degree of oxidn. Formic acid is the major volatile species identified, but the atm. relevance of its formation chem. needs to be further investigated. While successfully quantifying low mol. wt. org. oxygenates and tentatively identifying a reaction product formed directly from glyoxal and hydrogen peroxide, comparison of the results to the offline total org. carbon (TOC) anal. clearly shows that the AMS is not able to quant. monitor all dissolved orgs. in the bulk soln. This is likely due to their high volatility or low stability in the evapd. soln. droplets. This exptl. approach simulates atm. aq. phase processing by conducting oxidn. in the bulk phase, followed by evapn. of water and volatile orgs. to form SOA.
  16. 16
    Carrasquillo, A. J.; Hunter, J. F.; Daumit, K. E.; Kroll, J. H. Secondary Organic Aerosol Formation via the Isolation of Individual Reactive Intermediates: Role of Alkoxy Radical Structure. J. Phys. Chem. A 2014, 118 (38), 8807– 8816,  DOI: 10.1021/jp506562r
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    16
    Secondary Organic Aerosol Formation via the Isolation of Individual Reactive Intermediates: Role of Alkoxy Radical Structure
    Carrasquillo, Anthony J.; Hunter, James F.; Daumit, Kelly E.; Kroll, Jesse H.
    Journal of Physical Chemistry A (2014), 118 (38), 8807-8816CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
    The study of the chem. underlying secondary org. aerosol (SOA) formation is complicated by the large no. of reaction pathways and oxidn. generations available to a given precursor species. Here we simplify such complexity to that of a single alkoxy radical (RO), by forming SOA via the direct photolysis of alkyl nitrite (RONO) isomers. Chamber expts. were conducted with 11 C10 RONO isomers to det. how the position of the radical center and branching of the carbon skeleton influences SOA formation. SOA yields served as a probe of RO reactivity, with lower yields indicating that fragmentation reactions dominate and higher yields suggesting the predominance of RO isomerization. The largest yields were from straight-chain isomers, particularly those with radical centers located toward the terminus of the mol. Trends in SOA yields can be explained in terms of two major effects: (1) the relative importance of isomerization and fragmentation reactions, which control the distribution of products, and (2) differences in volatility among the various isomeric products formed. Yields from branched isomers, which were low but variable, provide insight into the degree of fragmentation of the alkoxy radicals; in the case of the two β-substituted alkoxy radicals, fragmentation appears to occur to a greater extent than predicted by structure-activity relationships. Our results highlight how subtle differences in alkoxy radical structure can have major impacts on product yields and SOA formation.
  17. 17
    Kessler, S. H.; Nah, T.; Carrasquillo, A. J.; Jayne, J. T.; Worsnop, D. R.; Wilson, K. R.; Kroll, J. H. Formation of Secondary Organic Aerosol from the Direct Photolytic Generation of Organic Radicals. J. Phys. Chem. Lett. 2011, 2 (11), 1295– 1300,  DOI: 10.1021/jz200432n
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    17
    Formation of Secondary Organic Aerosol from the Direct Photolytic Generation of Organic Radicals
    Kessler, Sean H.; Nah, Theodora; Carrasquillo, Anthony J.; Jayne, John T.; Worsnop, Douglas R.; Wilson, Kevin R.; Kroll, Jesse H.
    Journal of Physical Chemistry Letters (2011), 2 (11), 1295-1300CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
    The immense complexity inherent in secondary org. aerosol (SOA) formation, primarily due to the large no. of oxidn. steps and reaction pathways involved, has limited a detailed understanding of its underlying chem. To simplify such complexity, this work demonstrates SOA formation via photolysis of gas-phase alkyl iodides, generating org. peroxy radicals with known structures. In contrast to std. OH--initiated oxidn. expts., photolytically-initiated oxidn. forms a limited no. of products in a single reactive step. Typical for SOA, yields of aerosol generated from alkyl iodide photolysis depends on aerosol load, indicating the semi-volatile nature of the particulate species. However, aerosols were obsd. to have higher volatility and be less oxidized than previous multi-generational studies of alkane oxidn., suggesting addnl. oxidative steps are necessary to produce oxidized semi-volatile matter in the atm. Despite the relative simplicity of this chem. system, SOA mass spectra are still quite complex, underscoring the wide range of products present in SOA.
  18. 18
    Iglesias, E.; Casado, J. Mechanisms of Hydrolysis and Nitrosation Reactions of Alkyl Nitrites in Various Media. Int. Rev. Phys. Chem. 2002, 21 (1), 37– 74,  DOI: 10.1080/01442350110092693
    Google Scholar
    There is no corresponding record for this reference.
  19. 19
    Hunter, J. F.; Carrasquillo, A. J.; Daumit, K. E.; Kroll, J. H. Secondary Organic Aerosol Formation from Acyclic, Monocyclic, and Polycyclic Alkanes. Environ. Sci. Technol. 2014, 48 (17), 10227– 10234,  DOI: 10.1021/es502674s
    Google Scholar
    19
    Secondary organic aerosol formation from acyclic, monocyclic, and polycyclic alkanes
    Hunter, James F.; Carrasquillo, Anthony J.; Daumit, Kelly E.; Kroll, Jesse H.
    Environmental Science & Technology (2014), 48 (17), 10227-10234CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    A large no. of org. species emitted into the atm. contain cycloalkyl groups. While cyclic species are believed to be important secondary org. aerosol (SOA) precursors, the specific role of cyclic moieties (particularly for species with multiple or fused rings) remains uncertain. Here we examine the yields and compn. of SOA formed from the reaction of OH with a series of C10 (cyclo)alkanes, with 0-3 rings, in order to better understand the role of multiple cyclic moieties on aerosol formation pathways. A chamber oxidn. technique using high, sustained OH radical concns. was used to simulate long reaction times in the atm. This aging technique leads to higher yields than in previously reported chamber expts. Yields were highest for cyclic and polycyclic precursors, though yield exhibited little dependence on no. of rings. However, the oxygen-to-carbon ratio of the SOA was highest for the polycyclic precursors. These trends are consistent with aerosol formation requiring two generations of oxidn. and 3-4 oxygen-contg. functional groups in order to condense. Cyclic, unbranched structures are protected from fragmentation during the first oxidn. step, with C-C bond scission instead leading to ring opening, efficient functionalization, and high SOA yields. Fragmentation may occur during subsequent oxidn. steps, limiting yields by forming volatile products. Polycyclic structures can undergo multiple ring opening reactions, but do not have markedly higher yields, likely due to enhanced fragmentation in the second oxidn. step. By contrast, C-C bond scission for the linear and branched structures leads to fragmentation prior to condensation, resulting in low SOA yields. The results highlight the key roles of multigenerational chem. and susceptibility to fragmentation in the formation and evolution of SOA.
  20. 20
    Zaytsev, A.; Breitenlechner, M.; Koss, A. R.; Lim, C. Y.; Rowe, J. C.; Kroll, J. H.; Keutsch, F. N. Using Collision-Induced Dissociation to Constrain Sensitivity of Ammonia Chemical Ionization Mass Spectrometry (NH4+ CIMS) to Oxygenated Volatile Organic Compounds. Atmospheric Meas. Technol. 2019, 12 (3), 1861– 1870,  DOI: 10.5194/amt-12-1861-2019
    Google Scholar
    There is no corresponding record for this reference.
  21. 21
    Orlando, J. J.; Tyndall, G. S.; Wallington, T. J. The Atmospheric Chemistry of Alkoxy Radicals. Chem. Rev. 2003, 103 (12), 4657– 4690,  DOI: 10.1021/cr020527p
    Google Scholar
    21
    The Atmospheric Chemistry of Alkoxy Radicals
    Orlando, John J.; Tyndall, Geoffrey S.; Wallington, Timothy J.
    Chemical Reviews (Washington, DC, United States) (2003), 103 (12), 4657-4689CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review concerning the atm. chem. of alkoxy radicals and rates and mechanisms of various reaction pathways is given. Topics discussed include: exptl. methods used to study alkoxy radical chem.; alkoxy radical chem. (reaction with O2 [CH3O• + O2; C2H5O• + O2; 1-C3H7O•, 2-C2H7O•, 1-C4H9O•, 2-C2H9O•, 3-C5H11O• + O2; CH2ClO•, CFCl2CH2O• + O2; comparison with previous recommendations], dissocn. reactions [unsubstituted alkoxy radicals, β-hydroxyalkoxy radicals, other O-substituted alkoxy radicals, halogenated alkoxy radicals], isomerization reactions, other intramol. reactions [HCl elimination reactions, the ester rearrangement reaction], chem. activation); and conclusions and suggestions for further study.
  22. 22
    Atkinson, R. Rate Constants for the Atmospheric Reactions of Alkoxy Radicals: An Updated Estimation Method. Atmos. Environ. 2007, 41 (38), 8468– 8485,  DOI: 10.1016/j.atmosenv.2007.07.002
    Google Scholar
    22
    Rate constants for the atmospheric reactions of alkoxy radicals: An updated estimation method
    Atkinson, Roger
    Atmospheric Environment (2007), 41 (38), 8468-8485CODEN: AENVEQ; ISSN:1352-2310. (Elsevier Ltd.)
    Alkoxy radicals are key intermediates in the atm. degrdns. of volatile org. compds., and can typically undergo reaction with O2, unimol. decompn. or unimol. isomerization. Previous structure-reactivity relationships for the estn. of rate consts. for these processes for alkoxy radicals have been updated to incorporate recent kinetic data from abs. and relative rate studies. Temp.-dependent rate expressions are derived allowing rate consts. for all three of these alkoxy radical reaction pathways to be calcd. at atmospherically relevant temps.
  23. 23
    Jenkin, M. E.; Valorso, R.; Aumont, B.; Rickard, A. R. Estimation of Rate Coefficients and Branching Ratios for Reactions of Organic Peroxy Radicals for Use in Automated Mechanism Construction. Atmospheric Chem. Phys. 2019, 19 (11), 7691– 7717,  DOI: 10.5194/acp-19-7691-2019
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    23
    Estimation of rate coefficients and branching ratios for reactions of organic peroxy radicals for use in automated mechanism construction
    Jenkin, Michael E.; Valorso, Richard; Aumont, Bernard; Rickard, Andrew R.
    Atmospheric Chemistry and Physics (2019), 19 (11), 7691-7717CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
    Org. peroxy radicals (RO2), formed from the degrdn. of hydrocarbons and other volatile org. compds. (VOCs), play a key role in tropospheric oxidn. mechanisms. Several competing reactions may be available for a given RO2 radical, the relative rates of which depend on both the structure of RO2 and the ambient conditions. Published kinetics and branching ratio data are reviewed for the bimol. reactions of RO2 with NO, NO2, NO3, OH and HO2; and for their self-reactions and cross-reactions with other RO2 radicals. This information is used to define generic rate coeffs. and structure-activity relationship (SAR) methods that can be applied to the bimol. reactions of a series of important classes of hydrocarbon and oxygenated RO2 radicals. Information for selected unimol. isomerization reactions (i.e. H-atom shift and ring-closure reactions) is also summarized and discussed. The methods presented here are intended to guide the representation of RO2 radical chem. in the next generation of explicit detailed chem. mechanisms.
  24. 24
    Dahl, E. E.; Saltzman, E. S.; De Bruyn, W. J. The Aqueous Phase Yield of Alkyl Nitrates from ROO + NO: Implications for Photochemical Production in Seawater. Geophys. Res. Lett. 2003, 30 (6), 1271,  DOI: 10.1029/2002GL016811
    Google Scholar
    There is no corresponding record for this reference.
  25. 25
    Butkovskaya, N.; Kukui, A.; Le Bras, G. Pressure and Temperature Dependence of Methyl Nitrate Formation in the CH3O2 + NO Reaction. J. Phys. Chem. A 2012, 116 (24), 5972– 5980,  DOI: 10.1021/jp210710d
    Google Scholar
    25
    Pressure and Temperature Dependence of Methyl Nitrate Formation in the CH3O2 + NO Reaction
    Butkovskaya, Nadezhda; Kukui, Alexandre; Le Bras, Georges
    Journal of Physical Chemistry A (2012), 116 (24), 5972-5980CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
    The branching ratio β = k1b/k1a for the formation of Me nitrate, CH3ONO2, in the gas-phase CH3O2 + NO reaction, CH3O2 + NO → CH3O + NO2 (1a), CH3O2 + NO → CH3ONO2 (1b), has been detd. over the pressure and temp. ranges 50-500 Torr and 223-300 K, resp., using a turbulent flow reactor coupled with a chem. ionization mass spectrometer. At 298 K, the CH3ONO2 yield has been found to increase linearly with pressure from 0.33 ± 0.16% at 50 Torr to 0.80 ± 0.54% at 500 Torr (errors are 2σ). Decrease of temp. from 300 to 220 K leads to an increase of β by a factor of about 3 in the 100-200 Torr range. These data correspond to a value of β ≈ 1.0 ± 0.7% over the pressure and temp. ranges of the whole troposphere. Atm. concns. of CH3ONO2 roughly estd. using results of this work are in reasonable agreement with those obsd. in polluted environments and significantly higher compared with measurements in upper troposphere and lower stratosphere.
  26. 26
    Richards-Henderson, N. K.; Goldstein, A. H.; Wilson, K. R. Large Enhancement in the Heterogeneous Oxidation Rate of Organic Aerosols by Hydroxyl Radicals in the Presence of Nitric Oxide. J. Phys. Chem. Lett. 2015, 6 (22), 4451– 4455,  DOI: 10.1021/acs.jpclett.5b02121
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    26
    Large Enhancement in the Heterogeneous Oxidation Rate of Organic Aerosols by Hydroxyl Radicals in the Presence of Nitric Oxide
    Richards-Henderson, Nicole K.; Goldstein, Allen H.; Wilson, Kevin R.
    Journal of Physical Chemistry Letters (2015), 6 (22), 4451-4455CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
    In the troposphere, the heterogeneous lifetime of an org. mol. in an aerosol exposed to OH- is thought to be weeks, which is orders of magnitude slower than the analogous gas phase reactions (hours). This paper reports an unexpectedly large acceleration in the effective heterogeneous OH- reaction rate in the presence of NO. This 10-50 fold acceleration originates from free radical chain reactions, propagated by alkoxy radicals which form inside the aerosols by the NO reaction with peroxy radicals, which do not appear to produce chain-terminating products (e.g., alkyl nitrates), unlike gas phase mechanisms. A kinetic model, constrained by exptl. data, suggests that in polluted regions, heterogeneous oxidn. plays a much more prominent role in the daily chem. evolution of org. aerosols than previously believed.
  27. 27
    Renbaum, L. H.; Smith, G. D. Organic Nitrate Formation in the Radical-Initiated Oxidation of Model Aerosol Particles in the Presence of NOx. Phys. Chem. Chem. Phys. 2009, 11 (36), 8040– 8047,  DOI: 10.1039/b909239k
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    There is no corresponding record for this reference.
  28. 28
    Goldstein, S.; Lind, J.; Merenyi, G. Reaction of Organic Peroxyl Radicals with •NO2 and •NO in Aqueous Solution: Intermediacy of Organic Peroxynitrate and Peroxynitrite Species. J. Phys. Chem. A 2004, 108 (10), 1719– 1725,  DOI: 10.1021/jp037431z
    Google Scholar
    28
    Reaction of Organic Peroxyl Radicals with •NO2 and •NO in Aqueous Solution: Intermediacy of Organic Peroxynitrate and Peroxynitrite Species
    Goldstein, Sara; Lind, Johan; Merenyi, Gabor
    Journal of Physical Chemistry A (2004), 108 (10), 1719-1725CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
    In this work, we studied the reactions of alkyl peroxyl radicals with •NO2 and •NO using the pulse radiolysis technique. The rate consts. for the reaction of •NO2 with (CH3)2C(OH)CH2OO•, CH3OO•, and c-C5H9OO• vary between 7 × 108 and 1.5 × 109 M-1 s-1. The reaction produces relatively long-lived alkyl peroxynitrates, which are in equil. with the parent radicals and have no appreciable absorption above 270 nm. It is also shown that •NO adds rapidly to (CH3)2C(OH)CH2OO• and CH3OO• to form alkyl peroxynitrites. The rate consts. for these reactions were detd. to be 2.8 × 109 and 3.5 × 109 M-1 s-1, resp. However, in contrast to alkyl peroxynitrates, alkyl peroxynitrites do not accumulate. Rather, they decomp. rapidly via homolysis along the relatively weak O-O bond, initially forming a geminate pair. Most of this pair collapses in the cage to form an alkyl nitrate, RONO2, and about 14% diffuses out as free alkoxyl and •NO2 radicals. A thermokinetic anal. predicts the half-life of CH3OONO in water to be less than 1 μs, an est. that agrees well with previous exptl. findings of ours for other alkyl peroxynitrites. A comparison of aq. and gaseous thermochem. of alkyl peroxynitrates reveals that alkyl peroxyl radicals and the corresponding alkyl peroxynitrates are similarly solvated by water.
  29. 29
    Butkovskaya, N.; Kukui, A.; Le Bras, G. Pressure and Temperature Dependence of Ethyl Nitrate Formation in the C2H5O2 + NO Reaction. J. Phys. Chem. A 2010, 114 (2), 956– 964,  DOI: 10.1021/jp910003a
    Google Scholar
    29
    Pressure and Temperature Dependence of Ethyl Nitrate Formation in the C2H5O2 + NO Reaction
    Butkovskaya, Nadezhda; Kukui, Alexandre; Le Bras, Georges
    Journal of Physical Chemistry A (2010), 114 (2), 956-964CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
    The branching ratio β = k1b/k1a for the formation of Et nitrate, C2H5ONO2, in the gas-phase C2H5O2 + NO reaction, C2H5O2 + NO → C2H5O + NO2 (1a), C2H5O2 + NO → C2H5ONO2 (1b), was detd. over the pressure and temp. ranges 100-600 Torr and 223-298 K, resp., using a turbulent flow reactor (TFR)-ion-mol. reactor(IMR) coupled with a chem. ionization mass spectrometer. At 298 K the C2H5ONO2 yield was found to increase linearly with pressure from about 0.7% at 100 Torr to about 3% at 600 Torr. At each pressure, the branching ratio of C2H5ONO2 formation increases with the decrease of temp. The following parametrization equation has been derived in the pressure and temp. ranges of the study: β(P,T) (%) = (3.88 × 10-3·P (Torr) + 0.365)·(1 + 1500(1/T - 1/298)). The atm. implication of the results obtained is briefly discussed, in particular the impact of β on the evolution of Et nitrate in urban plumes.
  30. 30
    Butkovskaya, N. I.; Kukui, A.; Le Bras, G. Pressure Dependence of Iso-Propyl Nitrate Formation in the i-C3H7O2 + NO Reaction. Z. Für Phys. Chem. 2010, 224 (7–8), 1025– 1038,  DOI: 10.1524/zpch.2010.6139
    Google Scholar
    There is no corresponding record for this reference.
  31. 31
    Atkinson, R.; Aschmann, S. M.; Carter, W. P. L.; Winer, A. M.; Pitts, J. N. Alkyl Nitrate Formation from the Nitrogen Oxide (NOx)-Air Photooxidations of C2-C8 n-Alkanes. J. Phys. Chem. 1982, 86 (23), 4563– 4569,  DOI: 10.1021/j100220a022
    Google Scholar
    31
    Alkyl nitrate formation from the nitrogen oxide (NOx)-air photooxidations of C2-C8 n-alkanes
    Atkinson, Roger; Aschmann, Sara M.; Carter, William P. L.; Winer, Arthur M.; Pitts, James N., Jr.
    Journal of Physical Chemistry (1982), 86 (23), 4563-9CODEN: JPCHAX; ISSN:0022-3654.
    The yields of alkyl nitrates formed in the NOx-air photooxidns. of the homologous series of n-alkanes from C2H6 [74-84-0] through n-octane [111-65-9] were detd. at 299 ± 2 K and 735 torr total pressure for different chem. systems. Alkyl peroxy radicals were generated by reaction of the n-alkanes with OH radicals (generated from the photolysis of Me nitrite in air) or Cl atoms (from photolysis of Cl in air). The alkyl nitrate yields obtained from the 2 systems, cor. for secondary reactions, were in agreement within the exptl. errors and increased monotonically with the C no. of the n-alkane, from ≤1% for C2H6 to ∼333% for n-octane, with the yields apparently approaching a limit of ∼35% for larger n-alkanes. The relative yields of the various secondary alkyl nitrate isomers in the n-pentane through n-octane systems were in good agreement with those expected from OH radical or Cl atom reaction with the corresponding secondary C-H bonds. However, the relative yields of the primary alkyl nitrates in the C3H8 and C4H10 systems were lower than expected by a factor of ∼2. The data are consistent with the alkyl nitrates being formed almost entirely from the reaction of peroxy radicals with NO, and the ratios of the cor. alkyl nitrate yields thus reflect the fraction of RO2 radicals which react with NO to form alkyl nitrates. These nitrate yields from the reaction of RO2 radicals with NO are important inputs into chem. computer models of the atm. NOx-air photooxidns. of the larger n-alkanes.
  32. 32
    Piletic, I. R.; Edney, E. O.; Bartolotti, L. J. Barrierless Reactions with Loose Transition States Govern the Yields and Lifetimes of Organic Nitrates Derived from Isoprene. J. Phys. Chem. A 2017, 121 (43), 8306– 8321,  DOI: 10.1021/acs.jpca.7b08229
    Google Scholar
    32
    Barrierless Reactions with Loose Transition States Govern the Yields and Lifetimes of Organic Nitrates Derived from Isoprene
    Piletic, Ivan R.; Edney, Edward O.; Bartolotti, Libero J.
    Journal of Physical Chemistry A (2017), 121 (43), 8306-8321CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
    The chem. reaction mechanism of NO addn. to two β and δ isoprene hydroxy-peroxy radical isomers is examd. in detail using d. functional theory, coupled cluster methods, and the energy resolved master equation formalism to provide ests. of rate consts. and org. nitrate yields. At the M06-2x/aug-cc-pVTZ level, the potential energy surfaces of NO reacting with β-(1,2)-HO-IsopOO• and δ-Z-(1,4)-HO-IsopOO• possess barrierless reactions that produce alkoxy radicals/NO2 and org. nitrates. The nudged elastic band method was used to discover a loosely bound van der Waals (vdW) complex between NO2 and the alkoxy radical that is present in both exit reaction channels. Semiempirical master equation calcns. show that the β org. nitrate yield is 8.5 ± 3.7%. Addnl., a relatively low barrier to C-C bond scission was discovered in the β-vdW complex that leads to direct HONO formation in the gas phase with a yield of 3.1 ± 1.3%. The δ isomer produces a looser vdW complex with a smaller dissocn. barrier and a larger isomerization barrier, giving a 2.4 ± 0.8% org. nitrate yield that is relatively pressure and temp. insensitive. By considering all of these pathways, the first-generation NOx recycling efficiency from isoprene org. nitrates is estd. to be 21% and is expected to increase with decreasing NOx concn.
  33. 33
    Aschmann, S. M.; Arey, J.; Atkinson, R. Atmospheric Chemistry of Selected Hydroxycarbonyls. J. Phys. Chem. A 2000, 104 (17), 3998– 4003,  DOI: 10.1021/jp9939874
    Google Scholar
    33
    Atmospheric Chemistry of Selected Hydroxycarbonyls
    Aschmann, Sara M.; Arey, Janet; Atkinson, Roger
    Journal of Physical Chemistry A (2000), 104 (17), 3998-4003CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
    Using a relative rate method, rate consts. have been measured at 296 ± 2 K for the gas-phase reactions of the OH radical with 1-hydroxy-2-butanone, 3-hydroxy-2-butanone, 1-hydroxy-3-butanone, 1-hydroxy-2-methyl-3-butanone, 3-hydroxy-3-methyl-2-butanone, and 4-hydroxy-3-hexanone, with rate consts. (in units of 10-12 cm3 mol.-1 s-1) of 7.7 ± 1.7, 10.3 ± 2.2, 8.1 ± 1.8, 16.2 ± 3.4, 0.94 ± 0.37, and 15.1 ± 3.1, resp., where the error limits include the estd. overall uncertainty in the rate const. for the ref. compd. Rate consts. were also measured for reactions with NO3 radicals and O3. Rate consts. for the NO3 radical reactions (in units of 10-16 cm3 mol.-1 s-1) were 1-hydroxy-2-butanone, <9; 3-hydroxy-2-butanone, 6.5 ± 2.2; 1-hydroxy-3-butanone, <22; 1-hydroxy-2-methyl-3-butanone, <22; 3-hydroxy-3-methyl-2-butanone, <2; and 4-hydroxy-3-hexanone, 12 ± 4, where the error limits include the estd. overall uncertainties in the rate consts. for the ref. compds. No reactions with O3 were obsd., and upper limits to the rate consts. of <1.1 × 10-19 cm3 mol.-1 s-1 were derived for all six hydroxycarbonyls. The dominant tropospheric loss process for the hydroxycarbonyls studied here is calcd. to be by reaction with the OH radical.
  34. 34
    Barry, J. T.; Berg, D. J.; Tyler, D. R. Radical Cage Effects: The Prediction of Radical Cage Pair Recombination Efficiencies Using Microviscosity Across a Range of Solvent Types. J. Am. Chem. Soc. 2017, 139 (41), 14399– 14405,  DOI: 10.1021/jacs.7b04499
    Google Scholar
    34
    Radical Cage Effects: The Prediction of Radical Cage Pair Recombination Efficiencies Using Microviscosity Across a Range of Solvent Types
    Barry, Justin T.; Berg, Daniel J.; Tyler, David R.
    Journal of the American Chemical Society (2017), 139 (41), 14399-14405CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    This study reports a method for correlating the radical recombination efficiencies (FcP) of geminate radical cage pairs to the properties of the solvent. Although bulk viscosity (macroviscosity) is typically used to predict or interpret radical recombination efficiencies, the work reported here shows that microviscosity is a much better parameter. The use of microviscosity is valid over a range of different solvent system types, including nonpolar, arom., polar, and hydrogen bonding solvents. In addn., the relationship of FcP to microviscosity holds for solvent systems contg. mixts. of these solvent types. The microviscosities of the solvent systems were straightforwardly detd. by measuring the diffusion coeff. of an appropriate probe by NMR DOSY spectroscopy. By using solvent mixts., selective solvation was shown to not affect the correlation between FcP and microviscosity. In addn., neither solvent polarity nor radical rotation affects the correlation between FcP and the microviscosity.
  35. 35
    Pryor, W. A.; Squadrito, G. L. The Chemistry of Peroxynitrite: A Product from the Reaction of Nitric Oxide with Superoxide. Am. J. Physiol.-Lung Cell. Mol. Physiol. 1995, 268 (5), L699– L722,  DOI: 10.1152/ajplung.1995.268.5.L699
    Google Scholar
    There is no corresponding record for this reference.
  36. 36
    Miyamoto, H.; Yampolski, Y.; Young, C. L. IUPAC-NIST Solubility Data Series. 103. Oxygen and Ozone in Water, Aqueous Solutions, and Organic Liquids (Supplement to Solubility Data Series Volume 7). J. Phys. Chem. Ref. Data 2014, 43 (3), 033102,  DOI: 10.1063/1.4883876
    Google Scholar
    There is no corresponding record for this reference.
  37. 37
    Sprague, M. K.; Garland, E. R.; Mollner, A. K.; Bloss, C.; Bean, B. D.; Weichman, M. L.; Mertens, L. A.; Okumura, M.; Sander, S. P. Kinetics of n-Butoxy and 2-Pentoxy Isomerization and Detection of Primary Products by Infrared Cavity Ringdown Spectroscopy. J. Phys. Chem. A 2012, 116 (24), 6327– 6340,  DOI: 10.1021/jp212136r
    Google Scholar
    37
    Kinetics of n-Butoxy and 2-Pentoxy Isomerization and Detection of Primary Products by Infrared Cavity Ringdown Spectroscopy
    Sprague, Matthew K.; Garland, Eva R.; Mollner, Andrew K.; Bloss, Claire; Bean, Brian D.; Weichman, Marissa L.; Mertens, Laura A.; Okumura, Mitchio; Sander, Stanley P.
    Journal of Physical Chemistry A (2012), 116 (24), 6327-6340CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
    The primary products of n-butoxy and 2-pentoxy isomerization in the presence and absence of O2 have been detected using pulsed laser photolysis-cavity ring down spectroscopy (PLP-CRDS). Alkoxy radicals n-butoxy and 2-pentoxy were generated by photolysis of alkyl nitrite precursors (Bu nitrite or 2-pentyl nitrite, resp.), and the isomerization products with and without O2 were detected by IR cavity ring down spectroscopy 20 μs after the photolysis. We report the mid-IR OH stretch (ν1) absorption spectra for δ-HO-1-C4H8·, δ-HO-1-C4H8OO·, δ-HO-1-C5H10·, and δ-HO-1-C5H10OO·. The obsd. ν1 bands are similar in position and shape to the related alcs. (n-butanol and 2-pentanol), although the HOROO· absorption is slightly stronger than the HOR· absorption. We detd. the rate of isomerization relative to reaction with O2 for the n-butoxy and 2-pentoxy radicals by measuring the relative ν1 absorbance of HOROO· as a function of [O2]. At 295 K and 670 Torr of N2 or N2/O2, we found rate const. ratios of kisom/kO2 = 1.7 (±0.1) × 1019 cm-3 for n-butoxy and kisom/kO2 = 3.4(±0.4) × 1019 cm-3 for 2-pentoxy (2σ uncertainty). Using currently known rate consts. kO2 , we est. isomerization rates of kisom = 2.4 (±1.2) × 105 s-1 and kisom ≈ 3 × 105 s-1 for n-butoxy and 2-pentoxy radicals, resp., where the uncertainties are primarily due to uncertainties in kO2 . Because isomerization is predicted to be in the high pressure limit at 670 Torr, these relative rates are expected to be the same at atm. pressure. Our results include corrections for prompt isomerization of hot nascent alkoxy radicals as well as reaction with background NO and unimol. alkoxy decompn. We est. prompt isomerization yields under our conditions of 4 ± 2% and 5 ± 2% for n-butoxy and 2-pentoxy formed from photolysis of the alkyl nitrites at 351 nm. Our measured relative rate values are in good agreement with and more precise than previous end-product anal. studies conducted on the n-butoxy and 2-pentoxy systems. We show that reactions typically neglected in the anal. of alkoxy relative kinetics (decompn., recombination with NO, and prompt isomerization) may need to be included to obtain accurate values of kisom/kO2 .
  38. 38
    Kamath, D.; Mezyk, S. P.; Minakata, D. Elucidating the Elementary Reaction Pathways and Kinetics of Hydroxyl Radical-Induced Acetone Degradation in Aqueous Phase Advanced Oxidation Processes. Environ. Sci. Technol. 2018, 52 (14), 7763– 7774,  DOI: 10.1021/acs.est.8b00582
    Google Scholar
    38
    Elucidating the Elementary Reaction Pathways and Kinetics of Hydroxyl Radical-Induced Acetone Degradation in Aqueous Phase Advanced Oxidation Processes
    Kamath, Divya; Mezyk, Stephen P.; Minakata, Daisuke
    Environmental Science & Technology (2018), 52 (14), 7763-7774CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    Advanced oxidn. processes (AOPs) that produce highly reactive hydroxyl radicals are promising methods to destroy aq. org. contaminants. Hydroxyl radicals react rapidly and nonselectively with org. contaminants and degrade them into intermediates and transformation byproducts. Past studies have indicated that peroxyl radical reactions are responsible for the formation of many intermediate radicals and transformation byproducts. However, complex peroxyl radical reactions that produce identical transformation products make it difficult to exptl. study the elementary reaction pathways and kinetics. In this study, we used ab initio quantum mech. calcns. to identify the thermodynamically preferable elementary reaction pathways of hydroxyl radical-induced acetone degrdn. by calcg. the free energies of the reaction and predicting the corresponding reaction rate consts. by calcg. the free energies of activation. In addn., we solved the ordinary differential equations for each species participating in the elementary reactions to predict the concn. profiles for acetone and its transformation byproducts in an aq. phase UV/hydrogen peroxide AOP. Our ab initio quantum mech. calcns. found an insignificant contribution of Russell reaction mechanisms of peroxyl radicals, but significant involvement of HO2• in the peroxyl radical reactions. The predicted concn. profiles were compared with expts. in the literature, validating our elementary reaction-based kinetic model.
  39. 39
    Elford, P. E.; Roberts, B. P. EPR Studies of the Formation and Transformation of Isomeric Radicals [C3H5O]•. Rearrangement of the Allyloxyl Radical in Non-Aqueous Solution Involving a Formal 1,2-Hydrogen-Atom Shift Promoted by Alcohols. J. Chem. Soc., Perkin Trans. 1996, 2 (11), 2247– 2256,  DOI: 10.1039/P29960002247
    Google Scholar
    There is no corresponding record for this reference.
  40. 40
    Konya, K. G.; Paul, T.; Lin, S.; Lusztyk, J.; Ingold, K. U. Laser Flash Photolysis Studies on the First Superoxide Thermal Source. First Direct Measurements of the Rates of Solvent-Assisted 1,2-Hydrogen Atom Shifts and a Proposed New Mechanism for This Unusual Rearrangement. J. Am. Chem. Soc. 2000, 122 (31), 7518– 7527,  DOI: 10.1021/ja993570b
    Google Scholar
    40
    Laser Flash Photolysis Studies on the First Superoxide Thermal Source. First Direct Measurements of the Rates of Solvent-Assisted 1,2-Hydrogen Atom Shifts and a Proposed New Mechanism for This Unusual Rearrangement
    Konya, Klara G.; Paul, Thomas; Lin, Shuqiong; Lusztyk, Janusz; Ingold, K. U.
    Journal of the American Chemical Society (2000), 122 (31), 7518-7527CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    The thermal decompn. of bis(4-carboxybenzyl)hyponitrite (I; SOTS-1) in aerated water under physiol. conditions has previously been shown to give the superoxide radical anion in a yield of 40 mol % (Ingold, K. U.; et al. J. Am. Chem. Soc. 1997, 119, 12364). The abs. kinetics of the elementary reactions involved in the cascade of events leading from the first-formed water-sol. benzyloxyl radical to superoxide have been detd. by laser flash photolysis. On the basis of these kinetics it is concluded that SOTS-1 will be suitable for studies of superoxide-induced oxidative stress in most biol. systems. A water-assisted 1,2-H shift converting benzyloxyl into the benzyl ketyl radical is an important step in the above reaction cascade. The kinetics of the 1,2-H shift assisted by H2O, D2O, and a no. of nucleophilic alcs. have been measured for the first time. These data have led to a proposed new mechanism involving the initial formation of a ketyl radical anion and an oxonium cation which generally collapse to give the neutral ketyl radical as the first observable product on the time scale of our expts. (ca. 80 ns).
  41. 41
    Schuchmann, H.-P.; Sonntag, C. v. Methylperoxyl Radicals: A Study of the γ-Radiolysis of Methane in Oxygenated Aqueous Solutions. Z. Für Naturforschung B 1984, 39 (2), 217– 221,  DOI: 10.1515/znb-1984-0217
    Google Scholar
    There is no corresponding record for this reference.
  42. 42
    Schuchmann, H.-P.; von Sonntag, C. Photolysis at 185 nm of Dimethyl Ether in Aqueous Solution: Involvement of the Hydroxymethyl Radical. J. Photochem. 1981, 16 (3), 289– 295,  DOI: 10.1016/0047-2670(81)80039-1
    Google Scholar
    42
    Photolysis at 185 nm of dimethyl ether in aqueous solution: involvement of the hydroxymethyl radical
    Schuchmann, Heinz Peter; Von Sonntag, Clemens
    Journal of Photochemistry (1981), 16 (4), 289-95CODEN: JPCMAE; ISSN:0047-2670.
    The photolysis of Me2O in aq. soln. at 185 nm yielded CH4, H2, MeOH, (MeOCH2)2, HCHO, MeOCH2CH2OH, (HOCH2)2, EtOH, and MeOEt. These products are explained by three primary processes (formation of CH3O• + •CH3; CH3OCH2• + •H; and CH2O + CH4), the rearrangement process (CH3O•→•CH2OH) known to be undergone by alkoxyl radicals in aq. soln. and subsequent free-radical reactions. In aq. solns. the quantum yield of primary processes leading to products is smaller by about an order of magnitude than those in cyclohexane solns. or those previously found with similar ethers as pure liqs. This apparently means that water as a solvent has a quenching effect. In aq. solns. there is an excited species which is reactive towards N2O and a proton, leading to the formation of N2 and H2 resp. Free hydrated electrons generated by photoionization do not appear to be involved in these reactions.
  43. 43
    von Sonntag, C.; Schuchmann, H.-P. The Elucidation of Peroxyl Radical Reactions in Aqueous Solution with the Help of Radiation-Chemical Methods. Angew. Chem., Int. Ed. Engl. 1991, 30 (10), 1229– 1253,  DOI: 10.1002/anie.199112291
    Google Scholar
    There is no corresponding record for this reference.
  44. 44
    Fernández-Ramos, A.; Zgierski, M. Z. Theoretical Study of the Rate Constants and Kinetic Isotope Effects of the 1,2-Hydrogen-Atom Shift of Methoxyl and Benzyloxyl Radicals Assisted by Water. J. Phys. Chem. A 2002, 106 (44), 10578– 10583,  DOI: 10.1021/jp020917f
    Google Scholar
    44
    Theoretical Study of the Rate Constants and Kinetic Isotope Effects of the 1,2-Hydrogen-Atom Shift of Methoxyl and Benzyloxyl Radicals Assisted by Water
    Fernandez-Ramos, Antonio; Zgierski, Marek Z.
    Journal of Physical Chemistry A (2002), 106 (44), 10578-10583CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
    Rate consts. and kinetic isotope effects for the 1,2-H shift of methoxyl and benzyloxyl radicals were studied in the presence of water mols. The electronic structure calcns. were carried out at the UB3LYP/6-31G* level, and the dynamics calcns. were performed using the variational transition state theory with semiclassical multidimensional corrections for tunneling. The study deals with 1:1 and 1:2 radical-water complexes in the gas phase. It was found that water catalyzes these rearrangement reactions by forming a bridge contg. two water mols. The dynamics calcns. show that the methoxyl-water complexes react only very slowly. The rate consts. for 1:2 complexes with the benzyloxyl radical are in relative good agreement with the results of laser flash photolysis. The kinetic isotope effects calcd. using heavy water indicate that tunneling makes an important contribution in the 1:1 complex, whereas the contribution due to vibrations is more important for the 1:2 complexes. In both cases, the kinetic isotope effects are substantial. It is concluded that the 1,2-H shift for both radicals is catalyzed by two water mols. through a mechanism that involves the formation of a preliminary 1:1 complex.
  45. 45
    Sander, R. Compilation of Henry’s Law Constants (Version 4.0) for Water as Solvent. Atmospheric Chem. Phys. 2015, 15 (8), 4399– 4981,  DOI: 10.5194/acp-15-4399-2015
    Google Scholar
    There is no corresponding record for this reference.
  46. 46
    Mack, J.; Bolton, J. R. Photochemistry of Nitrite and Nitrate in Aqueous Solution: A Review. J. Photochem. Photobiol. Chem. 1999, 128 (1), 1– 13,  DOI: 10.1016/S1010-6030(99)00155-0
    Google Scholar
    46
    Photochemistry of nitrite and nitrate in aqueous solution: a review
    Mack, John; Bolton, James R.
    Journal of Photochemistry and Photobiology, A: Chemistry (1999), 128 (1-3), 1-14CODEN: JPPCEJ; ISSN:1010-6030. (Elsevier Science S.A.)
    It has long been known that the photolysis of nitrite and nitrate solns. results in the formation of OH radicals. The mechanism of NO3- photolysis has been the subject of considerable controversy in the literature, however. This review summarizes the exptl. work on NO2- and NO3- photolysis in the context of recent advances in the understanding of the chem. of the peroxynitrite anion (ONOO-) in biol. expts. ONOO- has been found to play a far more significant role in the overall reaction mechanism of NO3- photolysis than had previously been suspected. Research on NO2- and NO3- photolysis, as a pathway to the destruction of org. contaminants in natural waters, is summarized. The possible impact of NO2- and NO3- on Advanced Oxidn. Technologies (AOTs), in which OH radicals are used to initiate the destruction of hazardous org. pollutants in drinking water and industrial waste streams, is explored. A review with 133 refs.
  47. 47
    Méreau, R.; Rayez, M.-T.; Caralp, F.; Rayez, J.-C. Isomerisation Reactions of Alkoxy Radicals: Theoretical Study and Structure–Activity Relationships. Phys. Chem. Chem. Phys. 2003, 5 (21), 4828– 4833,  DOI: 10.1039/B307708J
    Google Scholar
    There is no corresponding record for this reference.

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  • Abstract

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    Figure 1

    Figure 1. : Time-resolved mass spectrometric signals for n-pentyl nitrite photolysis products, in three phases: (a) the gas phase, (b) the condensed organic phase, and (3) the aqueous phase. All measurements use the NH4+ CIMS, and formulas listed are those of the analytes (products are detected as the complexes with NH4+). Signals are smoothed over 15-s intervals and normalized to the dilution tracer, acetonitrile; t = 0 refers to the time at which UV lights are switched on.

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    Figure 2

    Figure 2. : Simplified reaction mechanism for the photolysis of n-pentyl nitrite. Detected closed-shell products are highlighted, with colors corresponding to the products shown in Figure 1.

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  • References

    This article references 47 other publications.

    1. 1
      Hoffmann, E. H.; Tilgner, A.; Schrödner, R.; Bräuer, P.; Wolke, R.; Herrmann, H. An Advanced Modeling Study on the Impacts and Atmospheric Implications of Multiphase Dimethyl Sulfide Chemistry. Proc. Natl. Acad. Sci. U. S. A. 2016, 113 (42), 11776– 11781,  DOI: 10.1073/pnas.1606320113
      1
      An advanced modeling study on the impacts and atmospheric implications of multiphase dimethyl sulfide chemistry
      Hoffmann, Erik Hans; Tilgner, Andreas; Schroedner, Roland; Braeuer, Peter; Wolke, Ralf; Herrmann, Hartmut
      Proceedings of the National Academy of Sciences of the United States of America (2016), 113 (42), 11776-11781CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
      Oceans dominate di-Me sulfide (DMS) emissions, the major natural S source. DMS is important for formation of non-sea salt sulfate (nss-SO42-) aerosols and secondary particulate matter over oceans; thus, it significantly affects global climate. The DMS oxidn. mechanism has been examd. in several different model studies; however, these studies had restricted oxidn. mechanisms which mainly under-represented important aq.-phase chem. processes. These neglected but highly effective processes strongly affect the direct product yields of DMS oxidn., thereby affecting the climatic influence of aerosols. To address these shortfalls, an extensive multiphase DMS chem. mechanism, the Chem. Aq. Phase Radical Mechanism DMS Module 1.0, was developed and used in detailed model assessments of multiphase DMS chem. in the marine boundary layer. Model studies confirmed the importance of aq. phase chem. for the fate of DMS and its oxidn. products. Aq. phase processes significantly reduced the SO2 yield and increased the Me sulfonic acid (MSA) yield, which is needed to close the gap between modeled and measured MSA concns. Simulations implied that multi-phase DMS oxidn. produces equal amts. of MSA and SO42-, a result with significant implications for nss-SO42- aerosol formation, cloud condensation nuclei concn., and cloud albedo over oceans. Results showed the deficiencies of parameterizations currently used in higher-scale models which only treat gas phase chem. Overall, the results showed treatment of DMS chem. in gas and aq. phases is essential to improve model prediction accuracy.
    2. 2
      George, I. J.; Abbatt, J. P. D. Heterogeneous Oxidation of Atmospheric Aerosol Particles by Gas-Phase Radicals. Nat. Chem. 2010, 2 (9), 713– 722,  DOI: 10.1038/nchem.806
      2
      Heterogeneous oxidation of atmospheric aerosol particles by gas-phase radicals
      George, I. J.; Abbatt, J. P. D.
      Nature Chemistry (2010), 2 (9), 713-722CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)
      A review concerning the heterogeneous oxidn. of org. and inorg. constituents of atm. aerosols by gas-phase radicals is given, focusing on the kinetics and reaction mechanisms and how they affect particle physicochem. properties (compn., size, d., hygroscopicity). Potential atm. impacts include: release of chem. reactive gases, e.g., halogens, aldehydes and org. acids; reactive loss of particle-borne mol. tracer and toxic species; and enhanced hygroscopic properties of aerosols which may improve their ability to form cloud droplets. Topics discussed include: radical uptake on atm. relevant surfaces; oxidn. of condensed-phase org. and inorg. compds.; particle physicochem. property modification; atm. implications; and outlook.
    3. 3
      Lambe, A. T.; Cappa, C. D.; Massoli, P.; Onasch, T. B.; Forestieri, S. D.; Martin, A. T.; Cummings, M. J.; Croasdale, D. R.; Brune, W. H.; Worsnop, D. R.; Davidovits, P. Relationship between Oxidation Level and Optical Properties of Secondary Organic Aerosol. Environ. Sci. Technol. 2013, 47 (12), 6349– 6357,  DOI: 10.1021/es401043j
      3
      Relationship between Oxidation Level and Optical Properties of Secondary Organic Aerosol
      Lambe, Andrew T.; Cappa, Christopher D.; Massoli, Paola; Onasch, Timothy B.; Forestieri, Sara D.; Martin, Alexander T.; Cummings, Molly J.; Croasdale, David R.; Brune, William H.; Worsnop, Douglas R.; Davidovits, Paul
      Environmental Science & Technology (2013), 47 (12), 6349-6357CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      Brown carbon (BrC), which may include secondary org. aerosol (SOA), can be a significant climate-forcing agent through its optical absorption properties; however, the overall contribution of SOA to BrC remains poorly understood. This work examd. correlations between oxidn. level and SOA optical properties. SOA was generated in a flow reactor in the absence of NOx by OH- oxidn. of gaseous precursors as surrogates for anthropogenic (naphthalene, tricyclo[5.2.1.02,6]decane), biomass burning (guaiacol), and biogenic (α-pinene) emissions. SOA chem. compn. was characterized by time-of-flight aerosol mass spectrometry. SOA mass-specific absorption cross sections (MAC) and refractive indexes were calcd. from real-time cavity ring-down photo-acoustic spectrometry measurements at 405 and 532 nm and from UV-vis spectrometry measurements of methanol exts. of filter-collected particles (300-600 nm). At 405 nm, SOA MAC values and imaginary refractive indexes increased with increasing oxidn. level and decreased with increasing wavelength, leading to negligible absorption at 532 nm. SOA real refractive indexes decreased with increasing oxidn. level. A literature study comparison suggested that under typical polluted conditions, the effect of NOx on SOA absorption was small. SOA may significantly contribute to atm. BrC; the magnitude depends on precursor type and oxidn. level.
    4. 4
      Galeazzo, T.; Valorso, R.; Li, Y.; Camredon, M.; Aumont, B.; Shiraiwa, M. Estimation of Secondary Organic Aerosol Viscosity from Explicit Modeling of Gas-Phase Oxidation of Isoprene and α-Pinene. Atmospheric Chem. Phys. 2021, 21 (13), 10199– 10213,  DOI: 10.5194/acp-21-10199-2021
      4
      Estimation of secondary organic aerosol viscosity from explicit modeling of gas-phase oxidation of isoprene and α-pinene
      Galeazzo, Tommaso; Valorso, Richard; Li, Ying; Camredon, Marie; Aumont, Bernard; Shiraiwa, Manabu
      Atmospheric Chemistry and Physics (2021), 21 (13), 10199-10213CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      Secondary org. aerosols (SOA) are major components of atm. fine particulate matter, affecting climate and air quality. Mounting evidence exists that SOA can adopt glassy and viscous semisolid states, impacting formation and partitioning of SOA. In this study, we apply the GECKO-A (Generator of Explicit Chem. and Kinetics of Orgs. in the Atm.) model to conduct explicit chem. modeling of isoprene photooxidn. and α-pinene ozonolysis and their subsequent SOA formation. The detailed gas-phase chem. schemes from GECKO-A are implemented into a box model and coupled to our recently developed glass transition temp. parameterizations, allowing us to predict SOA viscosity. The effects of chem. compn., relative humidity, mass loadings and mass accommodation on particle viscosity are investigated in comparison with measurements of SOA viscosity. The simulated viscosity of isoprene SOA agrees well with viscosity measurements as a function of relative humidity, while the model underestimates viscosity of α-pinene SOA by a few orders of magnitude. This difference may be due to missing processes in the model, including autoxidn. and particle-phase reactions, leading to the formation of high-molar-mass compds. that would increase particle viscosity. Addnl. simulations imply that kinetic limitations of bulk diffusion and redn. in mass accommodation coeff. may play a role in enhancing particle viscosity by suppressing condensation of semi-volatile compds. The developed model is a useful tool for anal. and investigation of the interplay among gas-phase reactions, particle chem. compn. and SOA phase state.
    5. 5
      Kroll, J. H.; Seinfeld, J. H. Chemistry of Secondary Organic Aerosol: Formation and Evolution of Low-Volatility Organics in the Atmosphere. Atmos. Environ. 2008, 42 (16), 3593– 3624,  DOI: 10.1016/j.atmosenv.2008.01.003
      5
      Chemistry of secondary organic aerosol: Formation and evolution of low-volatility organics in the atmosphere
      Kroll, Jesse H.; Seinfeld, John H.
      Atmospheric Environment (2008), 42 (16), 3593-3624CODEN: AENVEQ; ISSN:1352-2310. (Elsevier Ltd.)
      A review is given. Secondary org. aerosol (SOA), particulate matter composed of compds. formed from the atm. transformation of org. species, accounts for a substantial fraction of tropospheric aerosol. The formation of low-volatility (semivolatile and possibly nonvolatile) compds. that make up SOA is governed by a complex series of reactions of a large no. of org. species, so the exptl. characterization and theor. description of SOA formation presents a substantial challenge. We outline what is known about the chem. of formation and continuing transformation of low-volatility species in the atm. The primary focus is chem. processes that can change the volatility of org. compds.: (1) oxidn. reactions in the gas phase, (2) reactions in the particle phase, and (3) continuing chem. (in either phase) over several generations. Gas-phase oxidn. reactions can reduce volatility by the addn. of polar functional groups or increase it by the cleavage of carbon-carbon bonds; key branch points that control volatility are the initial attack of the oxidant, reactions of alkylperoxy (RO2) radicals, and reactions of alkoxy (RO) radicals. Reactions in the particle phase include oxidn. reactions as well as accretion reactions, non-oxidative processes leading to the formation of high-mol.-wt. species. Org. C in the atm. is continually subject to reactions in the gas and particle phases throughout its atm. lifetime (until lost by phys. deposition or oxidized to CO or CO2), implying continual changes in volatility over the timescales of several days. The volatility changes arising from these chem. reactions must be parameterized and included in models in order to gain a quant. and predictive understanding of SOA formation.
    6. 6
      Calvert, J. G.; Derwent, R. G.; Orlando, J. J.; Wallington, T. J.; Tyndall, G. S. Mechanisms of Atmospheric Oxidation of the Alkanes; Oxford University Press: Oxford, NY, 2008.
      There is no corresponding record for this reference.
    7. 7
      Atkinson, R.; Arey, J. Atmospheric Degradation of Volatile Organic Compounds. Chem. Rev. 2003, 103 (12), 4605– 4638,  DOI: 10.1021/cr0206420
      7
      Atmospheric Degradation of Volatile Organic Compounds
      Atkinson, Roger; Arey, Janet
      Chemical Reviews (Washington, DC, United States) (2003), 103 (12), 4605-4638CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review concerning the removal of biogenic and anthropogenic volatile org. compds. (VOC) emitted to the atm. through phys. (deposition) or chem. processes, or their atm. transformation is given. Topics discussed include: tropospheric VOC transformation processes (initial reactions and lifetimes, reaction mechanisms); atm. chem. of alkanes (kinetic data for initial OH- and NO3- reactions, reaction mechanism); atm. chem. of alkenes (rate consts. for initial reaction of alkenes with OH-, NO3-, and O3; mechanism of the OH- reaction; NO3- reaction; reaction with O3); arom. hydrocarbons (kinetics of OH- reactions, reactions of phenols, reactions of unsatd. 1,4-dicarbonyls and di-unsatd. 1,6-dicarbonyls); atm. reactions of oxygenated VOC (aldehydes, ketones, aliph. alcs., ethers, alkyl nitrates); and conclusions and future research needs (exptl. studies, theor. studies and crit. reviews and evaluations).
    8. 8
      Calvert, J. G.; Mellouki, A.; Orlando, J. J. Mechanisms of Atmospheric Oxidation of the Oxygenates; Oxford University Press: Oxford, NY, 2011. DOI: 10.1093/oso/9780195365818.005.0001 .
      There is no corresponding record for this reference.
    9. 9
      Leviss, D. H.; Van Ry, D. A.; Hinrichs, R. Z. Multiphase Ozonolysis of Aqueous α-Terpineol. Environ. Sci. Technol. 2016, 50 (21), 11698– 11705,  DOI: 10.1021/acs.est.6b03612
      9
      Multiphase Ozonolysis of Aqueous α-Terpineol
      Leviss, Dani H.; Van Ry, Daryl A.; Hinrichs, Ryan Z.
      Environmental Science & Technology (2016), 50 (21), 11698-11705CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      Multiphase ozonolysis of aq. orgs. presents a potential pathway for the formation of aq. secondary org. aerosol (aqSOA). We investigated the multiphase ozonolysis of α-terpineol, an oxygenated deriv. of limonene, and found that the reaction products and kinetics differ from the gas-phase ozonolysis of α-terpineol. One- and two-dimensional NMR spectroscopies along with GC-MS identified the aq. ozonolysis reaction products as trans- and cis-lactols [4-(5-hydroxy-2,2-dimethyltetrahydrofuran-3-yl)butan-2-one] and a lactone [4-hydroxy-4-methyl-3-(3-oxobutyl)-valeric acid gamma-lactone], which accounted for 46%, 27%, and 20% of the obsd. products, resp. Hydrogen peroxide was also formed in 10% yield consistent with a mechanism involving decompn. of hydroxyl hydroperoxide intermediates followed by hemiacetal ring closure. Multiphase reaction kinetics at gaseous ozone concns. of 131, 480, and 965 parts-per-billion were analyzed using a resistance model of net ozone uptake and found the second-order rate coeff. for the aq. reaction of α-terpineol + O3 to be 9.9(±3.3) × 106 M-1 s-1. Multiphase ozonolysis will therefore be competitive with multiphase oxidn. by hydroxyl radicals (OH) and ozonolysis of gaseous α-terpineol. We also measured product yields for the heterogeneous ozonolysis of α-terpineol adsorbed on glass, NaCl, and kaolinite, and identified the same three major products but with an increasing lactone yield of 33, 49, and 55% on these substrates, resp.
    10. 10
      Akimoto, H.; Hirokawa, J. Atmospheric Multiphase Chemistry: Fundamentals of Secondary Aerosol Formation; John Wiley & Sons, 2020. DOI: 10.1002/9781119422419 .
      There is no corresponding record for this reference.
    11. 11
      Thornberry, T.; Abbatt, J. P. D. Heterogeneous Reaction of Ozone with Liquid Unsaturated Fatty Acids: Detailed Kinetics and Gas-Phase Product Studies. Phys. Chem. Chem. Phys. 2004, 6 (1), 84– 93,  DOI: 10.1039/b310149e
      11
      Heterogeneous reaction of ozone with liquid unsaturated fatty acids: detailed kinetics and gas-phase product studies
      Thornberry, T.; Abbatt, J. P. D.
      Physical Chemistry Chemical Physics (2004), 6 (1), 84-93CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
      Detailed kinetic and product yield studies have been performed for the heterogeneous reaction between gas-phase ozone and three liq. fatty acids using a coated-wall flow tube and chem. ionization mass spectrometry. Gas-surface reaction probabilities for ozone loss of (8.0 ±1.0) × 10-4, (1.3 ±0.1) × 10-3, and (1.8 ±0.2) × 10-3 have been measured at room temp. (298 K) for oleic acid, linoleic acid, and linolenic acid, resp. The temp. dependence of the uptake coeffs. was found to be small and pos. Comparison of these results to the kinetics of the equiv. gas-phase reactions implies that there is a definite enhancement in the rate for the heterogeneous process due to entropic factors, i.e., due to collisional trapping of ozone in the surface layers of the liq., and a possible effect on the activation energy of the reaction. For linoleic acid, the reaction probability was found to be independent of relative humidity (up to 55%), to ±10%, at 263 K. Volatile reaction products were obsd. using proton-transfer-reaction mass spectrometry. Nonanal was obsd. with a 0.50 (±0.10) yield for the reaction with oleic acid, whereas hexanal and nonenal were obsd. for linoleic acid with 0.25 (±0.05) and 0.29 (±0.05) yields, resp. These results indicate that the primary ozonide formed initially in the reaction can decomp. via two equal probability pathways and that a secondary ozonide is not formed in high yield in the aldehydic channel. These reactions represent a source of oxygenates to the atm. and will modify the hygroscopic properties of aerosols.
    12. 12
      Adams, G. E.; Willson, R. L. Pulse Radiolysis Studies on the Oxidation of Organic Radicals in Aqueous Solution. Trans. Faraday Soc. 1969, 65, 2981,  DOI: 10.1039/tf9696502981
      12
      Pulse radiolysis studies on the oxidation of organic radicals in aqueous solution
      Adams, Gerald Edward; Willson, Robin Lindhope
      Transactions of the Faraday Society (1969), 65 (11), 2981-7CODEN: TFSOA4; ISSN:0014-7672.
      Pulse radiolysis has been used to measure directly the abs. rates of oxidn. by ferricyanide ion of various radicals produced by OH attack on org. solutes. These include mono-, di-, and polyhydroxylic compds., hydroxy acids, polyethylene oxides of mol. wt. 200, 6000, and 20,000 and the amino acid serine. Radicals produced by H abstraction from α-C atoms in alcs. are oxidized at, or near, diffusion-controlled rates, whereas the reactions are much slower for radicals formed by OH-attack elsewhere. The technique has been used to measure the percentage of OH attack at the α-position for a series of straight and branched-chain alcs. O competes with ferricyanide for radical oxidn. The data for O-contg. solns. fit a simple radical-competition scheme which has been used to measure rates of peroxy-radical formation. These approach diffusion-controlled limits.
    13. 13
      Schuchmann, M. N.; Von Sonntag, C. The Rapid Hydration of the Acetyl Radical. A Pulse Radiolysis Study of Acetaldehyde in Aqueous Solution. J. Am. Chem. Soc. 1988, 110 (17), 5698– 5701,  DOI: 10.1021/ja00225a019
      13
      The rapid hydration of the acetyl radical. A pulse radiolysis study of acetaldehyde in aqueous solution.
      Schuchmann, Man Nien; Von Sonntag, Clemens
      Journal of the American Chemical Society (1988), 110 (17), 5698-701CODEN: JACSAT; ISSN:0002-7863.
      In aq. soln. acetaldehyde and its hydrate are in a 0.8:1 equil. Hydroxyl radicals, generated by the pulse radiolysis of N2O-satd. water, react with acetaldehyde about 3 times faster than with the hydrate. The predominant radicals formed are the acetyl radical and its hydrated form, H-abstraction at Me occurring to only about 5-10%. The acetyl radical rapidly hydrates. Its rate of hydration is 2 × 106 times faster than that of acetaldehyde. The hydrated acetyl radical has been monitored by its rapid redn. of tetranitromethane, the formation of O2- in the presence of Oxygen, and its deprotonation at pH 11. The acetyl radical does not oxidize N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) on the pulse radiolysis time scale. The acetylperoxyl radical (formed in the presence of oxygen) reacts rapidly with TMPD, ascorbate, and O2-; it is the most strongly oxidizing peroxyl radical known so far. Data on the rate of water loss from the hydrated acetyl radical are considerably less accurate, but the rate const. in estd.
    14. 14
      Mezyk, S. P.; Elliot, A. J. Pulse Radiolysis of Iodate in Aqueous Solution. J. Chem. Soc. Faraday Trans. 1994, 90 (6), 831– 836,  DOI: 10.1039/ft9949000831
      There is no corresponding record for this reference.
    15. 15
      Lee, A. K. Y.; Zhao, R.; Gao, S. S.; Abbatt, J. P. D. Aqueous-Phase OH Oxidation of Glyoxal: Application of a Novel Analytical Approach Employing Aerosol Mass Spectrometry and Complementary Off-Line Techniques. J. Phys. Chem. A 2011, 115 (38), 10517– 10526,  DOI: 10.1021/jp204099g
      15
      Aqueous-phase OH oxidation of glyoxal: application of a novel analytical approach employing aerosol mass spectrometry and complementary off-line techniques
      Lee, Alex K. Y.; Zhao, R.; Gao, S. S.; Abbatt, J. P. D.
      Journal of Physical Chemistry A (2011), 115 (38), 10517-10526CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
      Aq.-phase chem. of glyoxal may play an important role in the formation of highly oxidized secondary org. aerosol (SOA) in the atm. In this work, we use a novel design of photochem. reactor that allows for simultaneous photo-oxidn. and atomization of a bulk soln. to study the aq.-phase OH oxidn. of glyoxal. By employing both online aerosol mass spectrometry (AMS) and offline ion chromatog. (IC) measurements, glyoxal and some major products including formic acid, glyoxylic acid, and oxalic acid in the reacting soln. were simultaneously quantified. This is the first attempt to use AMS in kinetics studies of this type. The results illustrate the formation of highly oxidized products that likely coexist with traditional SOA materials, thus, potentially improving model predictions of org. aerosol mass loading and degree of oxidn. Formic acid is the major volatile species identified, but the atm. relevance of its formation chem. needs to be further investigated. While successfully quantifying low mol. wt. org. oxygenates and tentatively identifying a reaction product formed directly from glyoxal and hydrogen peroxide, comparison of the results to the offline total org. carbon (TOC) anal. clearly shows that the AMS is not able to quant. monitor all dissolved orgs. in the bulk soln. This is likely due to their high volatility or low stability in the evapd. soln. droplets. This exptl. approach simulates atm. aq. phase processing by conducting oxidn. in the bulk phase, followed by evapn. of water and volatile orgs. to form SOA.
    16. 16
      Carrasquillo, A. J.; Hunter, J. F.; Daumit, K. E.; Kroll, J. H. Secondary Organic Aerosol Formation via the Isolation of Individual Reactive Intermediates: Role of Alkoxy Radical Structure. J. Phys. Chem. A 2014, 118 (38), 8807– 8816,  DOI: 10.1021/jp506562r
      16
      Secondary Organic Aerosol Formation via the Isolation of Individual Reactive Intermediates: Role of Alkoxy Radical Structure
      Carrasquillo, Anthony J.; Hunter, James F.; Daumit, Kelly E.; Kroll, Jesse H.
      Journal of Physical Chemistry A (2014), 118 (38), 8807-8816CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
      The study of the chem. underlying secondary org. aerosol (SOA) formation is complicated by the large no. of reaction pathways and oxidn. generations available to a given precursor species. Here we simplify such complexity to that of a single alkoxy radical (RO), by forming SOA via the direct photolysis of alkyl nitrite (RONO) isomers. Chamber expts. were conducted with 11 C10 RONO isomers to det. how the position of the radical center and branching of the carbon skeleton influences SOA formation. SOA yields served as a probe of RO reactivity, with lower yields indicating that fragmentation reactions dominate and higher yields suggesting the predominance of RO isomerization. The largest yields were from straight-chain isomers, particularly those with radical centers located toward the terminus of the mol. Trends in SOA yields can be explained in terms of two major effects: (1) the relative importance of isomerization and fragmentation reactions, which control the distribution of products, and (2) differences in volatility among the various isomeric products formed. Yields from branched isomers, which were low but variable, provide insight into the degree of fragmentation of the alkoxy radicals; in the case of the two β-substituted alkoxy radicals, fragmentation appears to occur to a greater extent than predicted by structure-activity relationships. Our results highlight how subtle differences in alkoxy radical structure can have major impacts on product yields and SOA formation.
    17. 17
      Kessler, S. H.; Nah, T.; Carrasquillo, A. J.; Jayne, J. T.; Worsnop, D. R.; Wilson, K. R.; Kroll, J. H. Formation of Secondary Organic Aerosol from the Direct Photolytic Generation of Organic Radicals. J. Phys. Chem. Lett. 2011, 2 (11), 1295– 1300,  DOI: 10.1021/jz200432n
      17
      Formation of Secondary Organic Aerosol from the Direct Photolytic Generation of Organic Radicals
      Kessler, Sean H.; Nah, Theodora; Carrasquillo, Anthony J.; Jayne, John T.; Worsnop, Douglas R.; Wilson, Kevin R.; Kroll, Jesse H.
      Journal of Physical Chemistry Letters (2011), 2 (11), 1295-1300CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      The immense complexity inherent in secondary org. aerosol (SOA) formation, primarily due to the large no. of oxidn. steps and reaction pathways involved, has limited a detailed understanding of its underlying chem. To simplify such complexity, this work demonstrates SOA formation via photolysis of gas-phase alkyl iodides, generating org. peroxy radicals with known structures. In contrast to std. OH--initiated oxidn. expts., photolytically-initiated oxidn. forms a limited no. of products in a single reactive step. Typical for SOA, yields of aerosol generated from alkyl iodide photolysis depends on aerosol load, indicating the semi-volatile nature of the particulate species. However, aerosols were obsd. to have higher volatility and be less oxidized than previous multi-generational studies of alkane oxidn., suggesting addnl. oxidative steps are necessary to produce oxidized semi-volatile matter in the atm. Despite the relative simplicity of this chem. system, SOA mass spectra are still quite complex, underscoring the wide range of products present in SOA.
    18. 18
      Iglesias, E.; Casado, J. Mechanisms of Hydrolysis and Nitrosation Reactions of Alkyl Nitrites in Various Media. Int. Rev. Phys. Chem. 2002, 21 (1), 37– 74,  DOI: 10.1080/01442350110092693
      There is no corresponding record for this reference.
    19. 19
      Hunter, J. F.; Carrasquillo, A. J.; Daumit, K. E.; Kroll, J. H. Secondary Organic Aerosol Formation from Acyclic, Monocyclic, and Polycyclic Alkanes. Environ. Sci. Technol. 2014, 48 (17), 10227– 10234,  DOI: 10.1021/es502674s
      19
      Secondary organic aerosol formation from acyclic, monocyclic, and polycyclic alkanes
      Hunter, James F.; Carrasquillo, Anthony J.; Daumit, Kelly E.; Kroll, Jesse H.
      Environmental Science & Technology (2014), 48 (17), 10227-10234CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      A large no. of org. species emitted into the atm. contain cycloalkyl groups. While cyclic species are believed to be important secondary org. aerosol (SOA) precursors, the specific role of cyclic moieties (particularly for species with multiple or fused rings) remains uncertain. Here we examine the yields and compn. of SOA formed from the reaction of OH with a series of C10 (cyclo)alkanes, with 0-3 rings, in order to better understand the role of multiple cyclic moieties on aerosol formation pathways. A chamber oxidn. technique using high, sustained OH radical concns. was used to simulate long reaction times in the atm. This aging technique leads to higher yields than in previously reported chamber expts. Yields were highest for cyclic and polycyclic precursors, though yield exhibited little dependence on no. of rings. However, the oxygen-to-carbon ratio of the SOA was highest for the polycyclic precursors. These trends are consistent with aerosol formation requiring two generations of oxidn. and 3-4 oxygen-contg. functional groups in order to condense. Cyclic, unbranched structures are protected from fragmentation during the first oxidn. step, with C-C bond scission instead leading to ring opening, efficient functionalization, and high SOA yields. Fragmentation may occur during subsequent oxidn. steps, limiting yields by forming volatile products. Polycyclic structures can undergo multiple ring opening reactions, but do not have markedly higher yields, likely due to enhanced fragmentation in the second oxidn. step. By contrast, C-C bond scission for the linear and branched structures leads to fragmentation prior to condensation, resulting in low SOA yields. The results highlight the key roles of multigenerational chem. and susceptibility to fragmentation in the formation and evolution of SOA.
    20. 20
      Zaytsev, A.; Breitenlechner, M.; Koss, A. R.; Lim, C. Y.; Rowe, J. C.; Kroll, J. H.; Keutsch, F. N. Using Collision-Induced Dissociation to Constrain Sensitivity of Ammonia Chemical Ionization Mass Spectrometry (NH4+ CIMS) to Oxygenated Volatile Organic Compounds. Atmospheric Meas. Technol. 2019, 12 (3), 1861– 1870,  DOI: 10.5194/amt-12-1861-2019
      There is no corresponding record for this reference.
    21. 21
      Orlando, J. J.; Tyndall, G. S.; Wallington, T. J. The Atmospheric Chemistry of Alkoxy Radicals. Chem. Rev. 2003, 103 (12), 4657– 4690,  DOI: 10.1021/cr020527p
      21
      The Atmospheric Chemistry of Alkoxy Radicals
      Orlando, John J.; Tyndall, Geoffrey S.; Wallington, Timothy J.
      Chemical Reviews (Washington, DC, United States) (2003), 103 (12), 4657-4689CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review concerning the atm. chem. of alkoxy radicals and rates and mechanisms of various reaction pathways is given. Topics discussed include: exptl. methods used to study alkoxy radical chem.; alkoxy radical chem. (reaction with O2 [CH3O• + O2; C2H5O• + O2; 1-C3H7O•, 2-C2H7O•, 1-C4H9O•, 2-C2H9O•, 3-C5H11O• + O2; CH2ClO•, CFCl2CH2O• + O2; comparison with previous recommendations], dissocn. reactions [unsubstituted alkoxy radicals, β-hydroxyalkoxy radicals, other O-substituted alkoxy radicals, halogenated alkoxy radicals], isomerization reactions, other intramol. reactions [HCl elimination reactions, the ester rearrangement reaction], chem. activation); and conclusions and suggestions for further study.
    22. 22
      Atkinson, R. Rate Constants for the Atmospheric Reactions of Alkoxy Radicals: An Updated Estimation Method. Atmos. Environ. 2007, 41 (38), 8468– 8485,  DOI: 10.1016/j.atmosenv.2007.07.002
      22
      Rate constants for the atmospheric reactions of alkoxy radicals: An updated estimation method
      Atkinson, Roger
      Atmospheric Environment (2007), 41 (38), 8468-8485CODEN: AENVEQ; ISSN:1352-2310. (Elsevier Ltd.)
      Alkoxy radicals are key intermediates in the atm. degrdns. of volatile org. compds., and can typically undergo reaction with O2, unimol. decompn. or unimol. isomerization. Previous structure-reactivity relationships for the estn. of rate consts. for these processes for alkoxy radicals have been updated to incorporate recent kinetic data from abs. and relative rate studies. Temp.-dependent rate expressions are derived allowing rate consts. for all three of these alkoxy radical reaction pathways to be calcd. at atmospherically relevant temps.
    23. 23
      Jenkin, M. E.; Valorso, R.; Aumont, B.; Rickard, A. R. Estimation of Rate Coefficients and Branching Ratios for Reactions of Organic Peroxy Radicals for Use in Automated Mechanism Construction. Atmospheric Chem. Phys. 2019, 19 (11), 7691– 7717,  DOI: 10.5194/acp-19-7691-2019
      23
      Estimation of rate coefficients and branching ratios for reactions of organic peroxy radicals for use in automated mechanism construction
      Jenkin, Michael E.; Valorso, Richard; Aumont, Bernard; Rickard, Andrew R.
      Atmospheric Chemistry and Physics (2019), 19 (11), 7691-7717CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      Org. peroxy radicals (RO2), formed from the degrdn. of hydrocarbons and other volatile org. compds. (VOCs), play a key role in tropospheric oxidn. mechanisms. Several competing reactions may be available for a given RO2 radical, the relative rates of which depend on both the structure of RO2 and the ambient conditions. Published kinetics and branching ratio data are reviewed for the bimol. reactions of RO2 with NO, NO2, NO3, OH and HO2; and for their self-reactions and cross-reactions with other RO2 radicals. This information is used to define generic rate coeffs. and structure-activity relationship (SAR) methods that can be applied to the bimol. reactions of a series of important classes of hydrocarbon and oxygenated RO2 radicals. Information for selected unimol. isomerization reactions (i.e. H-atom shift and ring-closure reactions) is also summarized and discussed. The methods presented here are intended to guide the representation of RO2 radical chem. in the next generation of explicit detailed chem. mechanisms.
    24. 24
      Dahl, E. E.; Saltzman, E. S.; De Bruyn, W. J. The Aqueous Phase Yield of Alkyl Nitrates from ROO + NO: Implications for Photochemical Production in Seawater. Geophys. Res. Lett. 2003, 30 (6), 1271,  DOI: 10.1029/2002GL016811
      There is no corresponding record for this reference.
    25. 25
      Butkovskaya, N.; Kukui, A.; Le Bras, G. Pressure and Temperature Dependence of Methyl Nitrate Formation in the CH3O2 + NO Reaction. J. Phys. Chem. A 2012, 116 (24), 5972– 5980,  DOI: 10.1021/jp210710d
      25
      Pressure and Temperature Dependence of Methyl Nitrate Formation in the CH3O2 + NO Reaction
      Butkovskaya, Nadezhda; Kukui, Alexandre; Le Bras, Georges
      Journal of Physical Chemistry A (2012), 116 (24), 5972-5980CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
      The branching ratio β = k1b/k1a for the formation of Me nitrate, CH3ONO2, in the gas-phase CH3O2 + NO reaction, CH3O2 + NO → CH3O + NO2 (1a), CH3O2 + NO → CH3ONO2 (1b), has been detd. over the pressure and temp. ranges 50-500 Torr and 223-300 K, resp., using a turbulent flow reactor coupled with a chem. ionization mass spectrometer. At 298 K, the CH3ONO2 yield has been found to increase linearly with pressure from 0.33 ± 0.16% at 50 Torr to 0.80 ± 0.54% at 500 Torr (errors are 2σ). Decrease of temp. from 300 to 220 K leads to an increase of β by a factor of about 3 in the 100-200 Torr range. These data correspond to a value of β ≈ 1.0 ± 0.7% over the pressure and temp. ranges of the whole troposphere. Atm. concns. of CH3ONO2 roughly estd. using results of this work are in reasonable agreement with those obsd. in polluted environments and significantly higher compared with measurements in upper troposphere and lower stratosphere.
    26. 26
      Richards-Henderson, N. K.; Goldstein, A. H.; Wilson, K. R. Large Enhancement in the Heterogeneous Oxidation Rate of Organic Aerosols by Hydroxyl Radicals in the Presence of Nitric Oxide. J. Phys. Chem. Lett. 2015, 6 (22), 4451– 4455,  DOI: 10.1021/acs.jpclett.5b02121
      26
      Large Enhancement in the Heterogeneous Oxidation Rate of Organic Aerosols by Hydroxyl Radicals in the Presence of Nitric Oxide
      Richards-Henderson, Nicole K.; Goldstein, Allen H.; Wilson, Kevin R.
      Journal of Physical Chemistry Letters (2015), 6 (22), 4451-4455CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      In the troposphere, the heterogeneous lifetime of an org. mol. in an aerosol exposed to OH- is thought to be weeks, which is orders of magnitude slower than the analogous gas phase reactions (hours). This paper reports an unexpectedly large acceleration in the effective heterogeneous OH- reaction rate in the presence of NO. This 10-50 fold acceleration originates from free radical chain reactions, propagated by alkoxy radicals which form inside the aerosols by the NO reaction with peroxy radicals, which do not appear to produce chain-terminating products (e.g., alkyl nitrates), unlike gas phase mechanisms. A kinetic model, constrained by exptl. data, suggests that in polluted regions, heterogeneous oxidn. plays a much more prominent role in the daily chem. evolution of org. aerosols than previously believed.
    27. 27
      Renbaum, L. H.; Smith, G. D. Organic Nitrate Formation in the Radical-Initiated Oxidation of Model Aerosol Particles in the Presence of NOx. Phys. Chem. Chem. Phys. 2009, 11 (36), 8040– 8047,  DOI: 10.1039/b909239k
      There is no corresponding record for this reference.
    28. 28
      Goldstein, S.; Lind, J.; Merenyi, G. Reaction of Organic Peroxyl Radicals with •NO2 and •NO in Aqueous Solution: Intermediacy of Organic Peroxynitrate and Peroxynitrite Species. J. Phys. Chem. A 2004, 108 (10), 1719– 1725,  DOI: 10.1021/jp037431z
      28
      Reaction of Organic Peroxyl Radicals with •NO2 and •NO in Aqueous Solution: Intermediacy of Organic Peroxynitrate and Peroxynitrite Species
      Goldstein, Sara; Lind, Johan; Merenyi, Gabor
      Journal of Physical Chemistry A (2004), 108 (10), 1719-1725CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
      In this work, we studied the reactions of alkyl peroxyl radicals with •NO2 and •NO using the pulse radiolysis technique. The rate consts. for the reaction of •NO2 with (CH3)2C(OH)CH2OO•, CH3OO•, and c-C5H9OO• vary between 7 × 108 and 1.5 × 109 M-1 s-1. The reaction produces relatively long-lived alkyl peroxynitrates, which are in equil. with the parent radicals and have no appreciable absorption above 270 nm. It is also shown that •NO adds rapidly to (CH3)2C(OH)CH2OO• and CH3OO• to form alkyl peroxynitrites. The rate consts. for these reactions were detd. to be 2.8 × 109 and 3.5 × 109 M-1 s-1, resp. However, in contrast to alkyl peroxynitrates, alkyl peroxynitrites do not accumulate. Rather, they decomp. rapidly via homolysis along the relatively weak O-O bond, initially forming a geminate pair. Most of this pair collapses in the cage to form an alkyl nitrate, RONO2, and about 14% diffuses out as free alkoxyl and •NO2 radicals. A thermokinetic anal. predicts the half-life of CH3OONO in water to be less than 1 μs, an est. that agrees well with previous exptl. findings of ours for other alkyl peroxynitrites. A comparison of aq. and gaseous thermochem. of alkyl peroxynitrates reveals that alkyl peroxyl radicals and the corresponding alkyl peroxynitrates are similarly solvated by water.
    29. 29
      Butkovskaya, N.; Kukui, A.; Le Bras, G. Pressure and Temperature Dependence of Ethyl Nitrate Formation in the C2H5O2 + NO Reaction. J. Phys. Chem. A 2010, 114 (2), 956– 964,  DOI: 10.1021/jp910003a
      29
      Pressure and Temperature Dependence of Ethyl Nitrate Formation in the C2H5O2 + NO Reaction
      Butkovskaya, Nadezhda; Kukui, Alexandre; Le Bras, Georges
      Journal of Physical Chemistry A (2010), 114 (2), 956-964CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
      The branching ratio β = k1b/k1a for the formation of Et nitrate, C2H5ONO2, in the gas-phase C2H5O2 + NO reaction, C2H5O2 + NO → C2H5O + NO2 (1a), C2H5O2 + NO → C2H5ONO2 (1b), was detd. over the pressure and temp. ranges 100-600 Torr and 223-298 K, resp., using a turbulent flow reactor (TFR)-ion-mol. reactor(IMR) coupled with a chem. ionization mass spectrometer. At 298 K the C2H5ONO2 yield was found to increase linearly with pressure from about 0.7% at 100 Torr to about 3% at 600 Torr. At each pressure, the branching ratio of C2H5ONO2 formation increases with the decrease of temp. The following parametrization equation has been derived in the pressure and temp. ranges of the study: β(P,T) (%) = (3.88 × 10-3·P (Torr) + 0.365)·(1 + 1500(1/T - 1/298)). The atm. implication of the results obtained is briefly discussed, in particular the impact of β on the evolution of Et nitrate in urban plumes.
    30. 30
      Butkovskaya, N. I.; Kukui, A.; Le Bras, G. Pressure Dependence of Iso-Propyl Nitrate Formation in the i-C3H7O2 + NO Reaction. Z. Für Phys. Chem. 2010, 224 (7–8), 1025– 1038,  DOI: 10.1524/zpch.2010.6139
      There is no corresponding record for this reference.
    31. 31
      Atkinson, R.; Aschmann, S. M.; Carter, W. P. L.; Winer, A. M.; Pitts, J. N. Alkyl Nitrate Formation from the Nitrogen Oxide (NOx)-Air Photooxidations of C2-C8 n-Alkanes. J. Phys. Chem. 1982, 86 (23), 4563– 4569,  DOI: 10.1021/j100220a022
      31
      Alkyl nitrate formation from the nitrogen oxide (NOx)-air photooxidations of C2-C8 n-alkanes
      Atkinson, Roger; Aschmann, Sara M.; Carter, William P. L.; Winer, Arthur M.; Pitts, James N., Jr.
      Journal of Physical Chemistry (1982), 86 (23), 4563-9CODEN: JPCHAX; ISSN:0022-3654.
      The yields of alkyl nitrates formed in the NOx-air photooxidns. of the homologous series of n-alkanes from C2H6 [74-84-0] through n-octane [111-65-9] were detd. at 299 ± 2 K and 735 torr total pressure for different chem. systems. Alkyl peroxy radicals were generated by reaction of the n-alkanes with OH radicals (generated from the photolysis of Me nitrite in air) or Cl atoms (from photolysis of Cl in air). The alkyl nitrate yields obtained from the 2 systems, cor. for secondary reactions, were in agreement within the exptl. errors and increased monotonically with the C no. of the n-alkane, from ≤1% for C2H6 to ∼333% for n-octane, with the yields apparently approaching a limit of ∼35% for larger n-alkanes. The relative yields of the various secondary alkyl nitrate isomers in the n-pentane through n-octane systems were in good agreement with those expected from OH radical or Cl atom reaction with the corresponding secondary C-H bonds. However, the relative yields of the primary alkyl nitrates in the C3H8 and C4H10 systems were lower than expected by a factor of ∼2. The data are consistent with the alkyl nitrates being formed almost entirely from the reaction of peroxy radicals with NO, and the ratios of the cor. alkyl nitrate yields thus reflect the fraction of RO2 radicals which react with NO to form alkyl nitrates. These nitrate yields from the reaction of RO2 radicals with NO are important inputs into chem. computer models of the atm. NOx-air photooxidns. of the larger n-alkanes.
    32. 32
      Piletic, I. R.; Edney, E. O.; Bartolotti, L. J. Barrierless Reactions with Loose Transition States Govern the Yields and Lifetimes of Organic Nitrates Derived from Isoprene. J. Phys. Chem. A 2017, 121 (43), 8306– 8321,  DOI: 10.1021/acs.jpca.7b08229
      32
      Barrierless Reactions with Loose Transition States Govern the Yields and Lifetimes of Organic Nitrates Derived from Isoprene
      Piletic, Ivan R.; Edney, Edward O.; Bartolotti, Libero J.
      Journal of Physical Chemistry A (2017), 121 (43), 8306-8321CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
      The chem. reaction mechanism of NO addn. to two β and δ isoprene hydroxy-peroxy radical isomers is examd. in detail using d. functional theory, coupled cluster methods, and the energy resolved master equation formalism to provide ests. of rate consts. and org. nitrate yields. At the M06-2x/aug-cc-pVTZ level, the potential energy surfaces of NO reacting with β-(1,2)-HO-IsopOO• and δ-Z-(1,4)-HO-IsopOO• possess barrierless reactions that produce alkoxy radicals/NO2 and org. nitrates. The nudged elastic band method was used to discover a loosely bound van der Waals (vdW) complex between NO2 and the alkoxy radical that is present in both exit reaction channels. Semiempirical master equation calcns. show that the β org. nitrate yield is 8.5 ± 3.7%. Addnl., a relatively low barrier to C-C bond scission was discovered in the β-vdW complex that leads to direct HONO formation in the gas phase with a yield of 3.1 ± 1.3%. The δ isomer produces a looser vdW complex with a smaller dissocn. barrier and a larger isomerization barrier, giving a 2.4 ± 0.8% org. nitrate yield that is relatively pressure and temp. insensitive. By considering all of these pathways, the first-generation NOx recycling efficiency from isoprene org. nitrates is estd. to be 21% and is expected to increase with decreasing NOx concn.
    33. 33
      Aschmann, S. M.; Arey, J.; Atkinson, R. Atmospheric Chemistry of Selected Hydroxycarbonyls. J. Phys. Chem. A 2000, 104 (17), 3998– 4003,  DOI: 10.1021/jp9939874
      33
      Atmospheric Chemistry of Selected Hydroxycarbonyls
      Aschmann, Sara M.; Arey, Janet; Atkinson, Roger
      Journal of Physical Chemistry A (2000), 104 (17), 3998-4003CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
      Using a relative rate method, rate consts. have been measured at 296 ± 2 K for the gas-phase reactions of the OH radical with 1-hydroxy-2-butanone, 3-hydroxy-2-butanone, 1-hydroxy-3-butanone, 1-hydroxy-2-methyl-3-butanone, 3-hydroxy-3-methyl-2-butanone, and 4-hydroxy-3-hexanone, with rate consts. (in units of 10-12 cm3 mol.-1 s-1) of 7.7 ± 1.7, 10.3 ± 2.2, 8.1 ± 1.8, 16.2 ± 3.4, 0.94 ± 0.37, and 15.1 ± 3.1, resp., where the error limits include the estd. overall uncertainty in the rate const. for the ref. compd. Rate consts. were also measured for reactions with NO3 radicals and O3. Rate consts. for the NO3 radical reactions (in units of 10-16 cm3 mol.-1 s-1) were 1-hydroxy-2-butanone, <9; 3-hydroxy-2-butanone, 6.5 ± 2.2; 1-hydroxy-3-butanone, <22; 1-hydroxy-2-methyl-3-butanone, <22; 3-hydroxy-3-methyl-2-butanone, <2; and 4-hydroxy-3-hexanone, 12 ± 4, where the error limits include the estd. overall uncertainties in the rate consts. for the ref. compds. No reactions with O3 were obsd., and upper limits to the rate consts. of <1.1 × 10-19 cm3 mol.-1 s-1 were derived for all six hydroxycarbonyls. The dominant tropospheric loss process for the hydroxycarbonyls studied here is calcd. to be by reaction with the OH radical.
    34. 34
      Barry, J. T.; Berg, D. J.; Tyler, D. R. Radical Cage Effects: The Prediction of Radical Cage Pair Recombination Efficiencies Using Microviscosity Across a Range of Solvent Types. J. Am. Chem. Soc. 2017, 139 (41), 14399– 14405,  DOI: 10.1021/jacs.7b04499
      34
      Radical Cage Effects: The Prediction of Radical Cage Pair Recombination Efficiencies Using Microviscosity Across a Range of Solvent Types
      Barry, Justin T.; Berg, Daniel J.; Tyler, David R.
      Journal of the American Chemical Society (2017), 139 (41), 14399-14405CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      This study reports a method for correlating the radical recombination efficiencies (FcP) of geminate radical cage pairs to the properties of the solvent. Although bulk viscosity (macroviscosity) is typically used to predict or interpret radical recombination efficiencies, the work reported here shows that microviscosity is a much better parameter. The use of microviscosity is valid over a range of different solvent system types, including nonpolar, arom., polar, and hydrogen bonding solvents. In addn., the relationship of FcP to microviscosity holds for solvent systems contg. mixts. of these solvent types. The microviscosities of the solvent systems were straightforwardly detd. by measuring the diffusion coeff. of an appropriate probe by NMR DOSY spectroscopy. By using solvent mixts., selective solvation was shown to not affect the correlation between FcP and microviscosity. In addn., neither solvent polarity nor radical rotation affects the correlation between FcP and the microviscosity.
    35. 35
      Pryor, W. A.; Squadrito, G. L. The Chemistry of Peroxynitrite: A Product from the Reaction of Nitric Oxide with Superoxide. Am. J. Physiol.-Lung Cell. Mol. Physiol. 1995, 268 (5), L699– L722,  DOI: 10.1152/ajplung.1995.268.5.L699
      There is no corresponding record for this reference.
    36. 36
      Miyamoto, H.; Yampolski, Y.; Young, C. L. IUPAC-NIST Solubility Data Series. 103. Oxygen and Ozone in Water, Aqueous Solutions, and Organic Liquids (Supplement to Solubility Data Series Volume 7). J. Phys. Chem. Ref. Data 2014, 43 (3), 033102,  DOI: 10.1063/1.4883876
      There is no corresponding record for this reference.
    37. 37
      Sprague, M. K.; Garland, E. R.; Mollner, A. K.; Bloss, C.; Bean, B. D.; Weichman, M. L.; Mertens, L. A.; Okumura, M.; Sander, S. P. Kinetics of n-Butoxy and 2-Pentoxy Isomerization and Detection of Primary Products by Infrared Cavity Ringdown Spectroscopy. J. Phys. Chem. A 2012, 116 (24), 6327– 6340,  DOI: 10.1021/jp212136r
      37
      Kinetics of n-Butoxy and 2-Pentoxy Isomerization and Detection of Primary Products by Infrared Cavity Ringdown Spectroscopy
      Sprague, Matthew K.; Garland, Eva R.; Mollner, Andrew K.; Bloss, Claire; Bean, Brian D.; Weichman, Marissa L.; Mertens, Laura A.; Okumura, Mitchio; Sander, Stanley P.
      Journal of Physical Chemistry A (2012), 116 (24), 6327-6340CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
      The primary products of n-butoxy and 2-pentoxy isomerization in the presence and absence of O2 have been detected using pulsed laser photolysis-cavity ring down spectroscopy (PLP-CRDS). Alkoxy radicals n-butoxy and 2-pentoxy were generated by photolysis of alkyl nitrite precursors (Bu nitrite or 2-pentyl nitrite, resp.), and the isomerization products with and without O2 were detected by IR cavity ring down spectroscopy 20 μs after the photolysis. We report the mid-IR OH stretch (ν1) absorption spectra for δ-HO-1-C4H8·, δ-HO-1-C4H8OO·, δ-HO-1-C5H10·, and δ-HO-1-C5H10OO·. The obsd. ν1 bands are similar in position and shape to the related alcs. (n-butanol and 2-pentanol), although the HOROO· absorption is slightly stronger than the HOR· absorption. We detd. the rate of isomerization relative to reaction with O2 for the n-butoxy and 2-pentoxy radicals by measuring the relative ν1 absorbance of HOROO· as a function of [O2]. At 295 K and 670 Torr of N2 or N2/O2, we found rate const. ratios of kisom/kO2 = 1.7 (±0.1) × 1019 cm-3 for n-butoxy and kisom/kO2 = 3.4(±0.4) × 1019 cm-3 for 2-pentoxy (2σ uncertainty). Using currently known rate consts. kO2 , we est. isomerization rates of kisom = 2.4 (±1.2) × 105 s-1 and kisom ≈ 3 × 105 s-1 for n-butoxy and 2-pentoxy radicals, resp., where the uncertainties are primarily due to uncertainties in kO2 . Because isomerization is predicted to be in the high pressure limit at 670 Torr, these relative rates are expected to be the same at atm. pressure. Our results include corrections for prompt isomerization of hot nascent alkoxy radicals as well as reaction with background NO and unimol. alkoxy decompn. We est. prompt isomerization yields under our conditions of 4 ± 2% and 5 ± 2% for n-butoxy and 2-pentoxy formed from photolysis of the alkyl nitrites at 351 nm. Our measured relative rate values are in good agreement with and more precise than previous end-product anal. studies conducted on the n-butoxy and 2-pentoxy systems. We show that reactions typically neglected in the anal. of alkoxy relative kinetics (decompn., recombination with NO, and prompt isomerization) may need to be included to obtain accurate values of kisom/kO2 .
    38. 38
      Kamath, D.; Mezyk, S. P.; Minakata, D. Elucidating the Elementary Reaction Pathways and Kinetics of Hydroxyl Radical-Induced Acetone Degradation in Aqueous Phase Advanced Oxidation Processes. Environ. Sci. Technol. 2018, 52 (14), 7763– 7774,  DOI: 10.1021/acs.est.8b00582
      38
      Elucidating the Elementary Reaction Pathways and Kinetics of Hydroxyl Radical-Induced Acetone Degradation in Aqueous Phase Advanced Oxidation Processes
      Kamath, Divya; Mezyk, Stephen P.; Minakata, Daisuke
      Environmental Science & Technology (2018), 52 (14), 7763-7774CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      Advanced oxidn. processes (AOPs) that produce highly reactive hydroxyl radicals are promising methods to destroy aq. org. contaminants. Hydroxyl radicals react rapidly and nonselectively with org. contaminants and degrade them into intermediates and transformation byproducts. Past studies have indicated that peroxyl radical reactions are responsible for the formation of many intermediate radicals and transformation byproducts. However, complex peroxyl radical reactions that produce identical transformation products make it difficult to exptl. study the elementary reaction pathways and kinetics. In this study, we used ab initio quantum mech. calcns. to identify the thermodynamically preferable elementary reaction pathways of hydroxyl radical-induced acetone degrdn. by calcg. the free energies of the reaction and predicting the corresponding reaction rate consts. by calcg. the free energies of activation. In addn., we solved the ordinary differential equations for each species participating in the elementary reactions to predict the concn. profiles for acetone and its transformation byproducts in an aq. phase UV/hydrogen peroxide AOP. Our ab initio quantum mech. calcns. found an insignificant contribution of Russell reaction mechanisms of peroxyl radicals, but significant involvement of HO2• in the peroxyl radical reactions. The predicted concn. profiles were compared with expts. in the literature, validating our elementary reaction-based kinetic model.
    39. 39
      Elford, P. E.; Roberts, B. P. EPR Studies of the Formation and Transformation of Isomeric Radicals [C3H5O]•. Rearrangement of the Allyloxyl Radical in Non-Aqueous Solution Involving a Formal 1,2-Hydrogen-Atom Shift Promoted by Alcohols. J. Chem. Soc., Perkin Trans. 1996, 2 (11), 2247– 2256,  DOI: 10.1039/P29960002247
      There is no corresponding record for this reference.
    40. 40
      Konya, K. G.; Paul, T.; Lin, S.; Lusztyk, J.; Ingold, K. U. Laser Flash Photolysis Studies on the First Superoxide Thermal Source. First Direct Measurements of the Rates of Solvent-Assisted 1,2-Hydrogen Atom Shifts and a Proposed New Mechanism for This Unusual Rearrangement. J. Am. Chem. Soc. 2000, 122 (31), 7518– 7527,  DOI: 10.1021/ja993570b
      40
      Laser Flash Photolysis Studies on the First Superoxide Thermal Source. First Direct Measurements of the Rates of Solvent-Assisted 1,2-Hydrogen Atom Shifts and a Proposed New Mechanism for This Unusual Rearrangement
      Konya, Klara G.; Paul, Thomas; Lin, Shuqiong; Lusztyk, Janusz; Ingold, K. U.
      Journal of the American Chemical Society (2000), 122 (31), 7518-7527CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      The thermal decompn. of bis(4-carboxybenzyl)hyponitrite (I; SOTS-1) in aerated water under physiol. conditions has previously been shown to give the superoxide radical anion in a yield of 40 mol % (Ingold, K. U.; et al. J. Am. Chem. Soc. 1997, 119, 12364). The abs. kinetics of the elementary reactions involved in the cascade of events leading from the first-formed water-sol. benzyloxyl radical to superoxide have been detd. by laser flash photolysis. On the basis of these kinetics it is concluded that SOTS-1 will be suitable for studies of superoxide-induced oxidative stress in most biol. systems. A water-assisted 1,2-H shift converting benzyloxyl into the benzyl ketyl radical is an important step in the above reaction cascade. The kinetics of the 1,2-H shift assisted by H2O, D2O, and a no. of nucleophilic alcs. have been measured for the first time. These data have led to a proposed new mechanism involving the initial formation of a ketyl radical anion and an oxonium cation which generally collapse to give the neutral ketyl radical as the first observable product on the time scale of our expts. (ca. 80 ns).
    41. 41
      Schuchmann, H.-P.; Sonntag, C. v. Methylperoxyl Radicals: A Study of the γ-Radiolysis of Methane in Oxygenated Aqueous Solutions. Z. Für Naturforschung B 1984, 39 (2), 217– 221,  DOI: 10.1515/znb-1984-0217
      There is no corresponding record for this reference.
    42. 42
      Schuchmann, H.-P.; von Sonntag, C. Photolysis at 185 nm of Dimethyl Ether in Aqueous Solution: Involvement of the Hydroxymethyl Radical. J. Photochem. 1981, 16 (3), 289– 295,  DOI: 10.1016/0047-2670(81)80039-1
      42
      Photolysis at 185 nm of dimethyl ether in aqueous solution: involvement of the hydroxymethyl radical
      Schuchmann, Heinz Peter; Von Sonntag, Clemens
      Journal of Photochemistry (1981), 16 (4), 289-95CODEN: JPCMAE; ISSN:0047-2670.
      The photolysis of Me2O in aq. soln. at 185 nm yielded CH4, H2, MeOH, (MeOCH2)2, HCHO, MeOCH2CH2OH, (HOCH2)2, EtOH, and MeOEt. These products are explained by three primary processes (formation of CH3O• + •CH3; CH3OCH2• + •H; and CH2O + CH4), the rearrangement process (CH3O•→•CH2OH) known to be undergone by alkoxyl radicals in aq. soln. and subsequent free-radical reactions. In aq. solns. the quantum yield of primary processes leading to products is smaller by about an order of magnitude than those in cyclohexane solns. or those previously found with similar ethers as pure liqs. This apparently means that water as a solvent has a quenching effect. In aq. solns. there is an excited species which is reactive towards N2O and a proton, leading to the formation of N2 and H2 resp. Free hydrated electrons generated by photoionization do not appear to be involved in these reactions.
    43. 43
      von Sonntag, C.; Schuchmann, H.-P. The Elucidation of Peroxyl Radical Reactions in Aqueous Solution with the Help of Radiation-Chemical Methods. Angew. Chem., Int. Ed. Engl. 1991, 30 (10), 1229– 1253,  DOI: 10.1002/anie.199112291
      There is no corresponding record for this reference.
    44. 44
      Fernández-Ramos, A.; Zgierski, M. Z. Theoretical Study of the Rate Constants and Kinetic Isotope Effects of the 1,2-Hydrogen-Atom Shift of Methoxyl and Benzyloxyl Radicals Assisted by Water. J. Phys. Chem. A 2002, 106 (44), 10578– 10583,  DOI: 10.1021/jp020917f
      44
      Theoretical Study of the Rate Constants and Kinetic Isotope Effects of the 1,2-Hydrogen-Atom Shift of Methoxyl and Benzyloxyl Radicals Assisted by Water
      Fernandez-Ramos, Antonio; Zgierski, Marek Z.
      Journal of Physical Chemistry A (2002), 106 (44), 10578-10583CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
      Rate consts. and kinetic isotope effects for the 1,2-H shift of methoxyl and benzyloxyl radicals were studied in the presence of water mols. The electronic structure calcns. were carried out at the UB3LYP/6-31G* level, and the dynamics calcns. were performed using the variational transition state theory with semiclassical multidimensional corrections for tunneling. The study deals with 1:1 and 1:2 radical-water complexes in the gas phase. It was found that water catalyzes these rearrangement reactions by forming a bridge contg. two water mols. The dynamics calcns. show that the methoxyl-water complexes react only very slowly. The rate consts. for 1:2 complexes with the benzyloxyl radical are in relative good agreement with the results of laser flash photolysis. The kinetic isotope effects calcd. using heavy water indicate that tunneling makes an important contribution in the 1:1 complex, whereas the contribution due to vibrations is more important for the 1:2 complexes. In both cases, the kinetic isotope effects are substantial. It is concluded that the 1,2-H shift for both radicals is catalyzed by two water mols. through a mechanism that involves the formation of a preliminary 1:1 complex.
    45. 45
      Sander, R. Compilation of Henry’s Law Constants (Version 4.0) for Water as Solvent. Atmospheric Chem. Phys. 2015, 15 (8), 4399– 4981,  DOI: 10.5194/acp-15-4399-2015
      There is no corresponding record for this reference.
    46. 46
      Mack, J.; Bolton, J. R. Photochemistry of Nitrite and Nitrate in Aqueous Solution: A Review. J. Photochem. Photobiol. Chem. 1999, 128 (1), 1– 13,  DOI: 10.1016/S1010-6030(99)00155-0
      46
      Photochemistry of nitrite and nitrate in aqueous solution: a review
      Mack, John; Bolton, James R.
      Journal of Photochemistry and Photobiology, A: Chemistry (1999), 128 (1-3), 1-14CODEN: JPPCEJ; ISSN:1010-6030. (Elsevier Science S.A.)
      It has long been known that the photolysis of nitrite and nitrate solns. results in the formation of OH radicals. The mechanism of NO3- photolysis has been the subject of considerable controversy in the literature, however. This review summarizes the exptl. work on NO2- and NO3- photolysis in the context of recent advances in the understanding of the chem. of the peroxynitrite anion (ONOO-) in biol. expts. ONOO- has been found to play a far more significant role in the overall reaction mechanism of NO3- photolysis than had previously been suspected. Research on NO2- and NO3- photolysis, as a pathway to the destruction of org. contaminants in natural waters, is summarized. The possible impact of NO2- and NO3- on Advanced Oxidn. Technologies (AOTs), in which OH radicals are used to initiate the destruction of hazardous org. pollutants in drinking water and industrial waste streams, is explored. A review with 133 refs.
    47. 47
      Méreau, R.; Rayez, M.-T.; Caralp, F.; Rayez, J.-C. Isomerisation Reactions of Alkoxy Radicals: Theoretical Study and Structure–Activity Relationships. Phys. Chem. Chem. Phys. 2003, 5 (21), 4828– 4833,  DOI: 10.1039/B307708J
      There is no corresponding record for this reference.

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    • Additional details on experimental methods, including a diagram of the experimental setup; additional results, including an analysis of the pH dependence of n-pentyl nitrite hydrolysis, an analysis of tubing effects on the observed kinetics, and results of low-NO gas-phase experiments; a detailed derivation of the kinetic model used for extracting rate constants and branching ratios; a comparison between modeled and measured time profiles (PDF)


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