Conformational Analysis And Stereoelectronic Effects In Trans-1,2-dihalocyclohexanes: 1h Nmr And Theoretical Investigation.

dc.creatorFreitas, Matheus P
dc.creatorRittner, Roberto
dc.creatorTormena, Cláudio F
dc.creatorAbraham, Raymond J
dc.date2005-Jun
dc.date2015-11-27T13:02:04Z
dc.date2015-11-27T13:02:04Z
dc.date.accessioned2018-03-29T01:00:46Z
dc.date.available2018-03-29T01:00:46Z
dc.identifierSpectrochimica Acta. Part A, Molecular And Biomolecular Spectroscopy. v. 61, n. 8, p. 1771-6, 2005-Jun.
dc.identifier1386-1425
dc.identifier10.1016/j.saa.2004.07.007
dc.identifierhttp://www.ncbi.nlm.nih.gov/pubmed/15863046
dc.identifierhttp://repositorio.unicamp.br/jspui/handle/REPOSIP/196244
dc.identifier15863046
dc.identifier.urihttp://repositorioslatinoamericanos.uchile.cl/handle/2250/1296477
dc.descriptionThe conformational equilibrium of trans-1,2-difluoro- (1), trans-1,2-dichloro- (2) and trans-1,2-dibromo-cyclohexane (3) was studied through a combined method of NMR, theoretical calculations and solvation theory. The solvent dependence of the 3JH1,H2 NMR coupling constants together with theoretical calculations allow the direct determination of the conformational equilibria without recourse to model compounds. The coupling constants were obtained with the aid of spectrum simulation, since these symmetric molecules present complex coupling systems. The observed couplings, when analysed by solvation theory and utilising DFT geometries (B3LYP/6-311+G**), gave energy values of E(ee) -E(aa) of 0.10, 0.95 and 1.40 kcalmol(-1) in the vapour phase for 1, 2 and 3, respectively, decreasing to -0.63, 0.36 and 0.93 kcalmol(-1) in CCl4 and to -1.91, -0.80 and -0.05 kcalmol(-1) in DMSO solution. The diaxial preference for all compounds is explained by natural bond orbital (NBO) analysis, which shows important hyperconjugative effects in this conformation. The gauche effect for compounds with more electronegative substituents, which are in gauche arrangement in the ee conformation, also plays a relevant role in more polar solvents.
dc.description61
dc.description1771-6
dc.languageeng
dc.relationSpectrochimica Acta. Part A, Molecular And Biomolecular Spectroscopy
dc.relationSpectrochim Acta A Mol Biomol Spectrosc
dc.rightsfechado
dc.rights
dc.sourcePubMed
dc.subjectCyclohexanes
dc.subjectHydrocarbons, Halogenated
dc.subjectMagnetic Resonance Spectroscopy
dc.subjectMolecular Conformation
dc.subjectMolecular Structure
dc.subjectStereoisomerism
dc.subjectThermodynamics
dc.titleConformational Analysis And Stereoelectronic Effects In Trans-1,2-dihalocyclohexanes: 1h Nmr And Theoretical Investigation.
dc.typeArtículos de revistas


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