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Rotational Barriers in Push-Pull Ethylenes: An Advanced Physical-Organic Project Including 2D EXSY and Computational Chemistry
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Abstract
An integrated upper-division physical-organic experiment for chemistry majors has been developed. It involves the determination and mechanistic interpretation of the C=C and C-N rotational barriers in a push-pull ethylene. In the course of the experiment students will synthesize an organic compound, acquire variable temperature 1D and 2D NMR spectra, and use computational quantum chemistry to gain a deeper understanding of the unique electronic features of the molecule. Low temperature 2D EXchange SpectroscopY (EXSY) is used to quantitate the rotational barriers in a series of solvents. The quantum mechanical calculations provide a means to compare the properties of the push-pull ethylene with a similar non-push-pull system. Analysis of the experimental and theoretical results leads to a nearly complete picture of how substituent effects can influence bond lengths, rotational barriers, and the electronic distribution in these ethylenes.
Keywords (Audience):
Upper-Division UndergraduateKeywords (Domain):
Laboratory InstructionKeywords (Subject):
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This article has been cited by 8 ACS Journal articles (5 most recent appear below).
Solvent Effects on Chemical Exchange in a Push–Pull Ethylene as Studied by NMR and Electronic Structure Calculations
Maysoon Ababneh-Khasawneh, Blythe E. Fortier-McGill, Marzia E. Occhionorelli, and Alex D. BainThe Journal of Physical Chemistry A2011 Article ASAPSolvent Effects on Chemical Exchange in a Push–Pull Ethylene as Studied by NMR and Electronic Structure Calculations
Maysoon Ababneh-Khasawneh, Blythe E. Fortier-McGill, Marzia E. Occhionorelli, and Alex D. BainThe Journal of Physical Chemistry A2011 Article ASAPNMR measurements of chemical exchange in a push–pull ethylene, dissolved in a number of different solvents, are presented. These are complemented by high-level electronic structure calculations, using both gas-phase conditions and those which simulate ...
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Syntheses, Structures, and Dimerizations of Ferrocenyl- and Fluorenylideneallenes: Push−Pull Multiple Bonds?
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NMR Exchange Spectroscopy
Holly C. Gaede2007 969 (), 176-189NMR Exchange Spectroscopy
Holly C. Gaede2007 969 (), 176-189Two-dimensional exchange spectroscopy (EXSY) is a useful approach for studying dynamic processes with NMR. This method may be used in undergraduate laboratories as an alternative to the established techniques of line shape analysis or saturation transfer. ...
Correlated MO Study of the Low-Barrier Intramolecular Motions in Donor−Acceptor Ethenes
Snezhana M. Bakalova, Luis Manuel Frutos, Jose Kaneti, and Obis CastañoThe Journal of Physical Chemistry A2005 109 (45), 10388-10395Correlated MO Study of the Low-Barrier Intramolecular Motions in Donor−Acceptor Ethenes
Snezhana M. Bakalova, Luis Manuel Frutos, Jose Kaneti, and Obis CastañoThe Journal of Physical Chemistry A2005 109 (45), 10388-10395Correlated MP2 and MCSCF MO calculations of several model push−pull ethenes in most cases indicate no great participation of excited singlet and triplet electronic configurations in either the minima or the transition structures for the suggested ...
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- Received: August 03, 2009
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