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Intramolecular Hydrogen Bonding in Disubstituted Ethanes: General Considerations and Methodology in Quantum Mechanical Calculations of the Conformational Equilibria of Succinamate Monoanion

Rudner, Mark S. and Kent, David R., IV and Goddard, William A., III and Roberts, John D. (2005) Intramolecular Hydrogen Bonding in Disubstituted Ethanes: General Considerations and Methodology in Quantum Mechanical Calculations of the Conformational Equilibria of Succinamate Monoanion. Journal of Physical Chemistry A, 109 (40). pp. 9083-9088. ISSN 1089-5639. http://resolver.caltech.edu/CaltechAUTHORS:20150930-125952115

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Abstract

The importance of intramolecular hydrogen bonding between the carboxylate oxygen and amide proton of succinamate anion has been investigated by quantum mechanical simulations as a function of solvent for comparison with conformational equilibria estimated by NMR spectroscopy. The focus is on those methodological considerations of general interest to the conformational equilibrium problem, which are also particularly relevant to the quantum calculations. The roughly planar symmetry of the amide and carboxylate substituents of succinamate anion and the possibility of intramolecular hydrogen-bond formation together suggest that the orientational degrees of freedom of the substituents could play an important role in the equilibrium of the CH_2−CH_2 torsion. To test this hypothesis, two-dimensional potential-energy surfaces (PESs) were mapped out from the quantum mechanical calculations, with coordinates corresponding to the CH_2−CH_2 torsional and amide group rotational degrees of freedom. The Boltzmann populations obtained from two-dimensional PESs and those obtained from a one-dimensional adiabatic surface for the CH_2−CH_2 torsion were compared with the experimental results. In these comparisons, the agreement of calculated gauche fractions with corresponding experimental values was checked, as well as the agreement between predicted coupling constants and those determined from experimental spectra. In polar protic and aprotic solvents, where highly polar trans conformations can be stabilized by dipole−dipole and hydrogen-bonding interactions with the solvent, the orientational degree of freedom of the amide substituent appears to play a sufficiently important role in the CH_2−CH_2 torsional equilibrium that it cannot be safely ignored in the simulations.


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http://dx.doi.org/10.1021/jp052953vDOIArticle
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ORCID:
AuthorORCID
Goddard, William A., III0000-0003-0097-5716
Additional Information:© 2005 American Chemical Society. Received: June 2, 2005. Publication Date (Web): September 17, 2005. Acknowledgment is made to the donors of the Petroleum Research Fund administered by the American Chemical Society, for support of this research. We are also deeply indebted to the National Science Foundation under grant CHE-0104273, the Summer Undergraduate Research Fellowship Program (SURF) at the California Institute of Technology, the Camille and Henry Dreyfus Foundation, Merck and Company, the E. I. Du Pont Company, and Dr. & Mrs. Chester M. McCloskey for their helpful financial assistance. D.R.K. is grateful for support of this research from a graduate fellowship from the Fannie and John Hertz Foundation. The computational resources at the MSC were provided by ARO-DURIP and ONR-DURIP. Other support for the MSC came from DOE, ONR, NSF, NIH, Chevron-Texaco, Nissan, Aventis, Berlex, Intel, and Beckman Institute.
Funders:
Funding AgencyGrant Number
American Chemical Society Petroleum Research FundUNSPECIFIED
NSFCHE-0104273
Caltech Summer Undergraduate Research Fellowship (SURF)UNSPECIFIED
Camille and Henry Dreyfus FoundationUNSPECIFIED
Merck and CompanyUNSPECIFIED
E. I. Du Pont CompanyUNSPECIFIED
Dr. and Mrs. Chester M. McCloskeyUNSPECIFIED
Fannie and John Hertz FoundationUNSPECIFIED
Army Research Office (ARO)UNSPECIFIED
Office of Naval Research (ONR)UNSPECIFIED
Department of Energy (DOE)UNSPECIFIED
NIHUNSPECIFIED
Chevron-TexacoUNSPECIFIED
NissanUNSPECIFIED
AventisUNSPECIFIED
BerlexUNSPECIFIED
IntelUNSPECIFIED
Caltech Beckman InstituteUNSPECIFIED
Record Number:CaltechAUTHORS:20150930-125952115
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20150930-125952115
Official Citation:Intramolecular Hydrogen Bonding in Disubstituted Ethanes:  General Considerations and Methodology in Quantum Mechanical Calculations of the Conformational Equilibria of Succinamate Monoanion Mark S. Rudner, David R. Kent, IV, William A. Goddard, III, and John D. Roberts The Journal of Physical Chemistry A 2005 109 (40), 9083-9088 DOI: 10.1021/jp052953v
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:60613
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:30 Sep 2015 21:12
Last Modified:30 Sep 2015 21:12

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