Molecular Orbital Calculations of Hydrogen Bonding in Ammonia - Formic Acid System in the Presence of Electric Fields

The effects of electric fields on hydrogen bonding in ammonia - formic acid system, are examined with STO-3G and 6-31 G(d) wavefunctions. This system was used in a previous work to model hydrogen bonding in crystalline amino acids and the calculations were performed at HF / STO-3G level. The results...

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Autores principales:	Parra - Mouchet,J. E., Zapata - Torres,G., Fink,W. H., Nash,P.
Lenguaje:	English
Publicado:	Sociedad Chilena de Química 2004
Materias:	hydrogen bonding electric field molecular orbitals amino acids reactivity descriptors
Acceso en línea:	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072004000100013
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spelling	oai:scielo:S0717-970720040001000132004-05-11Molecular Orbital Calculations of Hydrogen Bonding in Ammonia - Formic Acid System in the Presence of Electric FieldsParra - Mouchet,J. E.Zapata - Torres,G.Fink,W. H.Nash,P. hydrogen bonding electric field molecular orbitals amino acids reactivity descriptors The effects of electric fields on hydrogen bonding in ammonia - formic acid system, are examined with STO-3G and 6-31 G(d) wavefunctions. This system was used in a previous work to model hydrogen bonding in crystalline amino acids and the calculations were performed at HF / STO-3G level. The results on the relative position of the tautomeric equilibrium between the neutral and zwitterionic forms were explained in terms of the relative stabilization of the ionic partners as a function of their placement in positive and negative wells created by the external electric field. In order to rationalize those results at electronic structure level, in this paper we analyze the response of the molecular orbitals implicated in the hydrogen bridge, N··H··O, to various imposed external fields. It is found that the stabilization of the zwitterionic structure occurs due to the destabilization of the MO localized essentially at the nitrogen electron lone pair, n-orbital, and concomitant with the stabilization of the MO essentially localized at the functional oxygen electron lone pair, o-orbital. The stabilization of the neutral structure occurs in the opposite situation. In addition, these eigenvalues are shown to be adequate regional molecular descriptors of the base reactivity of amines and conjugated bases of carboxylic acids, in gas phase and in the presence of electric fieldsinfo:eu-repo/semantics/openAccessSociedad Chilena de QuímicaJournal of the Chilean Chemical Society v.49 n.1 20042004-03-01text/htmlhttp://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072004000100013en10.4067/S0717-97072004000100013
institution	Scielo Chile
collection	Scielo Chile
language	English
topic	hydrogen bonding electric field molecular orbitals amino acids reactivity descriptors
spellingShingle	hydrogen bonding electric field molecular orbitals amino acids reactivity descriptors Parra - Mouchet,J. E. Zapata - Torres,G. Fink,W. H. Nash,P. Molecular Orbital Calculations of Hydrogen Bonding in Ammonia - Formic Acid System in the Presence of Electric Fields
description	The effects of electric fields on hydrogen bonding in ammonia - formic acid system, are examined with STO-3G and 6-31 G(d) wavefunctions. This system was used in a previous work to model hydrogen bonding in crystalline amino acids and the calculations were performed at HF / STO-3G level. The results on the relative position of the tautomeric equilibrium between the neutral and zwitterionic forms were explained in terms of the relative stabilization of the ionic partners as a function of their placement in positive and negative wells created by the external electric field. In order to rationalize those results at electronic structure level, in this paper we analyze the response of the molecular orbitals implicated in the hydrogen bridge, N··H··O, to various imposed external fields. It is found that the stabilization of the zwitterionic structure occurs due to the destabilization of the MO localized essentially at the nitrogen electron lone pair, n-orbital, and concomitant with the stabilization of the MO essentially localized at the functional oxygen electron lone pair, o-orbital. The stabilization of the neutral structure occurs in the opposite situation. In addition, these eigenvalues are shown to be adequate regional molecular descriptors of the base reactivity of amines and conjugated bases of carboxylic acids, in gas phase and in the presence of electric fields
author	Parra - Mouchet,J. E. Zapata - Torres,G. Fink,W. H. Nash,P.
author_facet	Parra - Mouchet,J. E. Zapata - Torres,G. Fink,W. H. Nash,P.
author_sort	Parra - Mouchet,J. E.
title	Molecular Orbital Calculations of Hydrogen Bonding in Ammonia - Formic Acid System in the Presence of Electric Fields
title_short	Molecular Orbital Calculations of Hydrogen Bonding in Ammonia - Formic Acid System in the Presence of Electric Fields
title_full	Molecular Orbital Calculations of Hydrogen Bonding in Ammonia - Formic Acid System in the Presence of Electric Fields
title_fullStr	Molecular Orbital Calculations of Hydrogen Bonding in Ammonia - Formic Acid System in the Presence of Electric Fields
title_full_unstemmed	Molecular Orbital Calculations of Hydrogen Bonding in Ammonia - Formic Acid System in the Presence of Electric Fields
title_sort	molecular orbital calculations of hydrogen bonding in ammonia - formic acid system in the presence of electric fields
publisher	Sociedad Chilena de Química
publishDate	2004
url	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072004000100013
work_keys_str_mv	AT parramouchetje molecularorbitalcalculationsofhydrogenbondinginammoniaformicacidsysteminthepresenceofelectricfields AT zapatatorresg molecularorbitalcalculationsofhydrogenbondinginammoniaformicacidsysteminthepresenceofelectricfields AT finkwh molecularorbitalcalculationsofhydrogenbondinginammoniaformicacidsysteminthepresenceofelectricfields AT nashp molecularorbitalcalculationsofhydrogenbondinginammoniaformicacidsysteminthepresenceofelectricfields
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Molecular Orbital Calculations of Hydrogen Bonding in Ammonia - Formic Acid System in the Presence of Electric Fields

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