Orbital interactions and their effects on C-13 NMR chemical shifts for 4,6-disubstituted-2,2-dimethyl-1,3-dioxanes. A theoretical study

dc.creatorTormena, CF
dc.creatorDias, LC
dc.creatorRittner, R
dc.date2005
dc.date41821
dc.date2014-11-15T17:08:46Z
dc.date2015-11-26T17:20:54Z
dc.date2014-11-15T17:08:46Z
dc.date2015-11-26T17:20:54Z
dc.date.accessioned2018-03-29T00:08:27Z
dc.date.available2018-03-29T00:08:27Z
dc.identifierJournal Of Physical Chemistry A. Amer Chemical Soc, v. 109, n. 27, n. 6077, n. 6082, 2005.
dc.identifier1089-5639
dc.identifierWOS:000230468100014
dc.identifier10.1021/jp052048a
dc.identifierhttp://www.repositorio.unicamp.br/jspui/handle/REPOSIP/69699
dc.identifierhttp://www.repositorio.unicamp.br/handle/REPOSIP/69699
dc.identifierhttp://repositorio.unicamp.br/jspui/handle/REPOSIP/69699
dc.identifier.urihttp://repositorioslatinoamericanos.uchile.cl/handle/2250/1283241
dc.descriptionA theoretical study is employed to describe the orbital interactions involved in the conformers' stability, the energies for the stereoelectronic interactions, and the corresponding effects of these interactions on the molecular structure (bond lengths) for cis- and trans-4,6-disubstituted-2,2-dimethyl-1,3-dioxanes. For cis-4,6-disubstituted-2,2-dimethyl-1,3-dioxanes, two LPO->sigma*(C(2)-Me(8))(2)-Me(B) interactions are extremely important and the energies involved in these interactions are in the range 6.81-7.58 kcal mol(-1) for the LPO(1)->sigma*(C(2)-Me(8)) and 7.58-7.71 kcal mol(-1) for the LPO(3)->sigma*(C(2)-Me(8)) interaction. These two LPO->sigma*(C(2)-Me(8)) interactions cause an upfield shift, indicating an increased shielding (increased electron density) of the ketal carbon C(2) as well as the axial Me-(8) group in the chair conformation. These LPO-sigma*(C(2)-Me(8)) hyperconjugative anomeric type interactions can explain the C-13 NMR chemical shifts at 19 ppm for the axial methyl group "Me-(8)" and 98.5 ppm for the ketal carbon "C-(2)". The observed results for the trans derivatives showed that for compounds 2a-c (R = -CN, -C&3bond; CH, and -CHO, respectively) the chair conformation is predominant, whereas for 2d,f-h [-CH3, -Ph, -C6H4(p-NO2), -C6H4(p-OCH3) respectively] the twist-boat is the most stable compound and for 2e [-C(CH3)(3)] is the only form.
dc.description109
dc.description27
dc.description6077
dc.description6082
dc.languageen
dc.publisherAmer Chemical Soc
dc.publisherWashington
dc.publisherEUA
dc.relationJournal Of Physical Chemistry A
dc.relationJ. Phys. Chem. A
dc.rightsfechado
dc.sourceWeb of Science
dc.subjectCarbon-13 Magnetic Resonance
dc.subjectHydrogen Bond Lengths
dc.subjectH Coupling-constants
dc.subject1,3-diol Acetonides
dc.subject6-membered Heterocycles
dc.subjectAcceptor Ability
dc.subjectHyperconjugation
dc.subjectDensity
dc.subjectCyclohexane
dc.subjectSubstituent
dc.titleOrbital interactions and their effects on C-13 NMR chemical shifts for 4,6-disubstituted-2,2-dimethyl-1,3-dioxanes. A theoretical study
dc.typeArtículos de revistas


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