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Conformational analysis of 2,2-difluoroethylamine hydrochloride: double gauche effect

The gauche effect in fluorinated alkylammonium salts is well known and attributed either to an intramolecular hydrogen bond or to an electrostatic attraction between the positively charged nitrogen and the vicinal electronegative fluorine atom. This work reports the effect of adding a fluorine atom...

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Autores principales: Silla, Josué M, Duarte, Claudimar J, Cormanich, Rodrigo A, Rittner, Roberto, Freitas, Matheus P
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Beilstein-Institut 2014
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3999868/
https://www.ncbi.nlm.nih.gov/pubmed/24778743
http://dx.doi.org/10.3762/bjoc.10.84
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author Silla, Josué M
Duarte, Claudimar J
Cormanich, Rodrigo A
Rittner, Roberto
Freitas, Matheus P
author_facet Silla, Josué M
Duarte, Claudimar J
Cormanich, Rodrigo A
Rittner, Roberto
Freitas, Matheus P
author_sort Silla, Josué M
collection PubMed
description The gauche effect in fluorinated alkylammonium salts is well known and attributed either to an intramolecular hydrogen bond or to an electrostatic attraction between the positively charged nitrogen and the vicinal electronegative fluorine atom. This work reports the effect of adding a fluorine atom in 2-fluoroethylamine hydrochloride on the conformational isomerism of the resulting 2,2-difluoroethylamine chloride (2). The analysis was carried out using NMR coupling constants in D(2)O solution, in order to mimic the equilibrium conditions in a physiological medium, in the gas phase and in implicit water through theoretical calculations. Despite the presence of σ(CH)→σ*(CF) and σ(CH)→σ*(CN) interactions, which usually rule the hyperconjugative gauche effect in 1,2-disubstituted ethanes, the most important forces leading to the double gauche effect ((+)NH(3) in the gauche relationship with both fluorine atoms) in 2 are the Lewis-type ones. Particularly, electrostatic interactions are operative even in water solution, where they should be significantly attenuated, whereas hyperconjugation and hydrogen bond have secondary importance.
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spelling pubmed-39998682014-04-28 Conformational analysis of 2,2-difluoroethylamine hydrochloride: double gauche effect Silla, Josué M Duarte, Claudimar J Cormanich, Rodrigo A Rittner, Roberto Freitas, Matheus P Beilstein J Org Chem Full Research Paper The gauche effect in fluorinated alkylammonium salts is well known and attributed either to an intramolecular hydrogen bond or to an electrostatic attraction between the positively charged nitrogen and the vicinal electronegative fluorine atom. This work reports the effect of adding a fluorine atom in 2-fluoroethylamine hydrochloride on the conformational isomerism of the resulting 2,2-difluoroethylamine chloride (2). The analysis was carried out using NMR coupling constants in D(2)O solution, in order to mimic the equilibrium conditions in a physiological medium, in the gas phase and in implicit water through theoretical calculations. Despite the presence of σ(CH)→σ*(CF) and σ(CH)→σ*(CN) interactions, which usually rule the hyperconjugative gauche effect in 1,2-disubstituted ethanes, the most important forces leading to the double gauche effect ((+)NH(3) in the gauche relationship with both fluorine atoms) in 2 are the Lewis-type ones. Particularly, electrostatic interactions are operative even in water solution, where they should be significantly attenuated, whereas hyperconjugation and hydrogen bond have secondary importance. Beilstein-Institut 2014-04-16 /pmc/articles/PMC3999868/ /pubmed/24778743 http://dx.doi.org/10.3762/bjoc.10.84 Text en Copyright © 2014, Silla et al. https://creativecommons.org/licenses/by/2.0https://www.beilstein-journals.org/bjoc/termsThis is an Open Access article under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The license is subject to the Beilstein Journal of Organic Chemistry terms and conditions: (https://www.beilstein-journals.org/bjoc/terms)
spellingShingle Full Research Paper
Silla, Josué M
Duarte, Claudimar J
Cormanich, Rodrigo A
Rittner, Roberto
Freitas, Matheus P
Conformational analysis of 2,2-difluoroethylamine hydrochloride: double gauche effect
title Conformational analysis of 2,2-difluoroethylamine hydrochloride: double gauche effect
title_full Conformational analysis of 2,2-difluoroethylamine hydrochloride: double gauche effect
title_fullStr Conformational analysis of 2,2-difluoroethylamine hydrochloride: double gauche effect
title_full_unstemmed Conformational analysis of 2,2-difluoroethylamine hydrochloride: double gauche effect
title_short Conformational analysis of 2,2-difluoroethylamine hydrochloride: double gauche effect
title_sort conformational analysis of 2,2-difluoroethylamine hydrochloride: double gauche effect
topic Full Research Paper
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3999868/
https://www.ncbi.nlm.nih.gov/pubmed/24778743
http://dx.doi.org/10.3762/bjoc.10.84
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