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Thermodynamics of Electron Attachment to Pyrimidine and Styrene in Supercritical Ethane

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Richard A. Holroyd*

Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973

Masaru Nishikawa

Faculty of Engineering, Kanagawa Institute of Technology, 1030 Shimo-Ogino, Astugi 243-0292, Japan

Kengo Itoh

Department of Pure and Applied Science, University of Tokyo, Tokyo, 153-8902, Japan

J. Phys. Chem. B, 1999, 103 (43), pp 9205–9210

DOI: 10.1021/jp990717c

Publication Date (Web): June 19, 1999

Section:

Thermodynamics, Thermochemistry, and Thermal Properties

Abstract

The reaction of excess electrons with pyrimidine and styrene was studied in supercritical ethane. The equilibrium constant for attachment was large when the solute was pyrimidine and small for styrene, although their electron affinities are comparable. At pressures above 100 bar, the rate constant for electron attachment to pyrimidine (k_a) was time resolved using the short pulse of the laser-electron accelerator facility (LEAF). The rate constant, k_a, is large and nearly independent of pressure and temperature; thus, the volume of activation is close to zero. At lower pressures, the equilibrium constants for this reaction were derived from the changes in the mobility of excess electrons. The free energy is a function of the polarization energy, which was evaluated with a compressible continuum model. The small equilibrium constant in the case of styrene is attributed to a smaller polarization energy. Values of ΔV_r, obtained from changes of ΔG_r with pressure, range from −9.0 to −0.4 L/mol. The observed volume changes are compared to electrostriction volumes calculated by the model. Electron attachment occurs with a large decrease in entropy associated with clustering of ethane molecules around the ion formed. Observed values of ΔS_r are comparable to expected values calculated from ΔS_r = (α/χ_T)ΔV_r.

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This article has been cited by 3 ACS Journal articles (3 most recent appear below).

Energetics and Volume Changes in Electron Attachment to Pyrazine in Supercritical Xenon
Richard A. Holroyd and Jack M. Preses, Masaru Nishikawa, Kengo Itoh
The Journal of Physical Chemistry B2007 111 (24), 6684-6689
- Energetics and Volume Changes in Electron Attachment to Pyrazine in Supercritical Xenon
  Richard A. Holroyd and Jack M. Preses, Masaru Nishikawa, Kengo Itoh
  The Journal of Physical Chemistry B2007 111 (24), 6684-6689
  The attachment of electrons to pyrazine occurs reversibly over a wide range of pressures at and above room temperature in supercritical xenon. The rate constant for attachment increases with pressure at low pressures, passes through a maximum, and levels ...
  Abstract | Full Text HTML | Hi-Res PDF | PDF w/ Links
Properties and Reactions of Charged Species in Nonpolar Supercritical Fluids
Richard Holroyd, Masaru Nishikawa, Kengo Itoh
The Journal of Physical Chemistry B2005 109 (7), 2478-2486
- Properties and Reactions of Charged Species in Nonpolar Supercritical Fluids
  Richard Holroyd, Masaru Nishikawa, Kengo Itoh
  The Journal of Physical Chemistry B2005 109 (7), 2478-2486
  This review focuses on the properties and reactions of charged species in supercritical fluids. The techniques of pulse conductivity and transient absorption are used to follow the behavior of charged species. We begin with a discussion of the mobilities, ...
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Negative Charge Transport in Gaseous, Supercritical, and Liquid Carbon Dioxide
Kengo Itoh, Azusa Muraoka, Kazuo Watanabe, and Takashi Nagata, Masaru Nishikawa, Richard A. Holroyd
The Journal of Physical Chemistry B2004 108 (28), 10177-10184
- Negative Charge Transport in Gaseous, Supercritical, and Liquid Carbon Dioxide
  Kengo Itoh, Azusa Muraoka, Kazuo Watanabe, and Takashi Nagata, Masaru Nishikawa, Richard A. Holroyd
  The Journal of Physical Chemistry B2004 108 (28), 10177-10184
  The mobility of one of two types of fast moving negative charge carriers was measured by a time-of-flight method over a wide range of the solvent density ρ in gaseous, supercritical, and liquid carbon dioxide. Charge carriers are formed by laser ...
  Abstract | Full Text HTML | Hi-Res PDF | PDF w/ Links