Substituent effects on H-1 and C-13 NMR chemical shifts in alpha-monosubstituted ethyl acetates: principal component analysis and H-1 chemical shift calculations

dc.creatorTasic, L
dc.creatorAbraham, RJ
dc.creatorRittner, R
dc.date2002
dc.dateJUL
dc.date2014-11-14T09:55:54Z
dc.date2015-11-26T16:05:50Z
dc.date2014-11-14T09:55:54Z
dc.date2015-11-26T16:05:50Z
dc.date.accessioned2018-03-28T22:54:49Z
dc.date.available2018-03-28T22:54:49Z
dc.identifierMagnetic Resonance In Chemistry. Wiley-blackwell, v. 40, n. 7, n. 449, n. 454, 2002.
dc.identifier0749-1581
dc.identifierWOS:000176373300004
dc.identifier10.1002/mrc.1046
dc.identifierhttp://www.repositorio.unicamp.br/jspui/handle/REPOSIP/74677
dc.identifierhttp://www.repositorio.unicamp.br/handle/REPOSIP/74677
dc.identifierhttp://repositorio.unicamp.br/jspui/handle/REPOSIP/74677
dc.identifier.urihttp://repositorioslatinoamericanos.uchile.cl/handle/2250/1265803
dc.descriptionA principal component analysis is applied to a-monosubstituted ethyl acetates (YCH2CO2Et), where the observed chemical shifts for the a-carbon atom, the carbonyl carbon, and the a-hydrogen atoms are correlated with theoretically derived molecular properties, i.e. the partial charges on the same atoms and the electronegativity and hardness. The effects on H-1 and C-13 NMR chemical shifts of 12 alpha-substituents: F, Cl, Br, I, OMe, OEt, SMe, SEt, NMe2, NEt2, Me, and Et were investigated. A strong grouping of the same heteroatom substituents is observed, showing the chemical shift dependence on the type of substituent. Halogenated compounds represent a heterogeneous group, where the large effect of the fluorine substituent is similar to that of the oxygen derivatives (OMe and OEt). Theoretical calculations show that fluorine and oxygen derivatives exhibit similar energy curves with respect to the Y-C-C=O dihedral angle and the same conformational equilibrium between cis and trans rotamers. Sulfur, neutral substituents and halogen derivatives (Cl, Br and I) give an equilibrium between cis and gauche rotamers, with a predominance of the gauche conformers. The rotational equilibrium in solution was confirmed by H-1 chemical shift calculations utilizing the CHARGE 7H program. The calculated a-hydrogen atom chemical shifts are in very good agreement with the measured values. Copyright (C) 2002 John Wiley Sons, Ltd.
dc.description40
dc.description7
dc.description449
dc.description454
dc.languageen
dc.publisherWiley-blackwell
dc.publisherMalden
dc.publisherEUA
dc.relationMagnetic Resonance In Chemistry
dc.relationMagn. Reson. Chem.
dc.rightsfechado
dc.rightshttp://olabout.wiley.com/WileyCDA/Section/id-406071.html
dc.sourceWeb of Science
dc.subjectNMR
dc.subjectH-1
dc.subjectC-13
dc.subjectprincipal component analysis
dc.subjectH-1 chemical shift calculations
dc.subjectsubstituent effects
dc.subjectalpha-monosubstituted ethyl acetates
dc.subjectChemometric Analysis
dc.subjectSpectroscopy
dc.subjectBenzenes
dc.subjectDensity
dc.titleSubstituent effects on H-1 and C-13 NMR chemical shifts in alpha-monosubstituted ethyl acetates: principal component analysis and H-1 chemical shift calculations
dc.typeArtículos de revistas


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