Influence of OH center dot center dot center dot N and NH center dot center dot center dot O inter- and intramolecular hydrogen bonds in the conformational equilibrium of some 1,3-disubstituted cyclohexanes through NMR spectroscopy and theoretical calculations

dc.creatorde Oliveira, PR
dc.creatorViesser, RV
dc.creatorGuerrero, PG
dc.creatorRittner, R
dc.date2011
dc.dateMAY
dc.date2014-08-01T18:31:44Z
dc.date2015-11-26T17:00:41Z
dc.date2014-08-01T18:31:44Z
dc.date2015-11-26T17:00:41Z
dc.date.accessioned2018-03-28T23:48:29Z
dc.date.available2018-03-28T23:48:29Z
dc.identifierSpectrochimica Acta Part A-molecular And Biomolecular Spectroscopy. Pergamon-elsevier Science Ltd, v. 78, n. 5, n. 1599, n. 1605, 2011.
dc.identifier1386-1425
dc.identifierWOS:000289864300039
dc.identifier10.1016/j.saa.2011.02.010
dc.identifierhttp://www.repositorio.unicamp.br/jspui/handle/REPOSIP/80232
dc.identifierhttp://repositorio.unicamp.br/jspui/handle/REPOSIP/80232
dc.identifier.urihttp://repositorioslatinoamericanos.uchile.cl/handle/2250/1278541
dc.descriptionFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
dc.descriptionConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
dc.descriptionCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
dc.descriptionThe analysis of concentration effects in the (1)H NMR data of cis-3-aminocyclohexanol (ACOL) showed that its diequatorial conformer changes from 60%at 0.01 mol L(-1) to 70% at 0.40 mol L(-1) in acetone-d(6). A similar increase was also observed for the diequatorial conformer of cis-3-N-methylaminocyclohexanol (MCOL), from 32% (CDCl(3) 0.01 mol L(-1)) to 55% (CDCl(3) 0.40 mol L(-1)). The increase in solvent basicity leads to a large stabilization effect for the diequatorial conformer of both compounds too. For ACOL, it changes from 47% (Delta G(egeq-axax) = 0.06 kcal mol(-1)) in CCl(4) to 93% (Delta G(eqeq-axax) = -1.53 kcal mol(-1)) in DMSO, while for MCOL it goes from 7% (Delta G(egeq-axax) = 1.54 kcal mol(-1)) in CCl(4) to 82% (Delta G(egeq-axax) = -0.88 kcal mol(-1)) in pyridine-d(6). These results indicate that the intramolecular hydrogen bonds (IAHB) OH center dot center dot center dot N and NH center dot center dot center dot O stabilize the diaxial conformers of these compounds in a non-polar solvent. For cis-3-amino-1 -methoxycyclohexane (ACNE) and cis-3-N-methylamino-1-methoxy-cyclohexane (MCNE) no changes were observed in equilibrium with the variation of solvent polarity. These results indicate for the first time that the IAHB NH center dot center dot center dot O is not strong enough to stabilize the diaxial conformer of these compounds and that the conformation equilibria of the cis isomers of compounds ACOL and MCOL are influenced only by the IAHB OH center dot center dot center dot N. Moreover, the presence of a secondary amino group (93% of diaxial conformer in CCl(4)) leads to an IAHB OH center dot center dot center dot N stronger than in primary and tertiary amino-derivatives (53 and 54% of diaxial conformer, respectively) for 1,3-disubstituted cyclohexanes. Values obtained from the theoretical data through the B3LYP functional are in agreement with the experimental results and indicate that the IAHB strength that influences the conformational equilibrium of these compounds is the IAHB OH center dot center dot center dot N. Thus, the IAHB NH center dot center dot center dot O do not stabilize the diaxial conformer of the cis isomer of compounds ACNE and MCNE showing that the diequatonal conformer will always be more stable than the diaxial conformer, independent of concentration or solvent. (C) 2011 Elsevier B.V. All rights reserved.
dc.description78
dc.description5
dc.description1599
dc.description1605
dc.descriptionFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
dc.descriptionConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
dc.descriptionCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
dc.descriptionFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
dc.descriptionConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
dc.descriptionCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
dc.languageen
dc.publisherPergamon-elsevier Science Ltd
dc.publisherOxford
dc.publisherInglaterra
dc.relationSpectrochimica Acta Part A-molecular And Biomolecular Spectroscopy
dc.relationSpectroc. Acta Pt. A-Molec. Biomolec. Spectr.
dc.rightsfechado
dc.rightshttp://www.elsevier.com/about/open-access/open-access-policies/article-posting-policy
dc.sourceWeb of Science
dc.subjectConformational analysis
dc.subjectNMR spectroscopy
dc.subjectTheoretical calculations
dc.subjectIntramolecular hydrogen bond
dc.subjectAminocyclohexanols
dc.subjectDensity
dc.subjectExchange
dc.titleInfluence of OH center dot center dot center dot N and NH center dot center dot center dot O inter- and intramolecular hydrogen bonds in the conformational equilibrium of some 1,3-disubstituted cyclohexanes through NMR spectroscopy and theoretical calculations
dc.typeArtículos de revistas


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