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Type: Artigo de periódico
Title: Theoretical and infrared spectroscopy study of the conformational preferences for some 3-monosubstituted-2-methylpropenes
Author: Schuquel, ITA
Pontes, RM
Freitas, MP
Rittner, R
Abstract: The infrared spectra of 3-X-2-methylpropenes (X = Cl, Br, I, NMe(2), NEt(2), OH, OMe, OEt, SH, SMe and SEt) have been recorded at room temperature in CCl(4) solution. The C=C stretching mode was analyzed and compared to theoretically calculated data to give insight about the conformational isomerism of these compounds. A combination band systematically appears in all spectra (except for amines); the remaining nu(C=C) band and the corresponding intensities were used to obtain the conformer populations. For second-period atoms bonded to C-3, two or more conformers are observed in CCl(4) solution, but when substitution by heavier atoms takes place, only one conformer is observed under the tested conditions, i.e., the gauche form with respect to the C=C C X dihedral angle. Therefore, steric hindrance between X and =CH(2) in the s-cis form is strongly dependent on the heteroatom size, while the effect of the alkyl chain bonded to the heteroatom seems to be of secondary importance. (C) 2011 Elsevier B.V. All rights reserved.
Subject: 3-Monosubstituted 2-methylpropenes
Methallyl compounds
Conformational studies
Ab initio and OFF calculations
nu(c)=(c) stretching frequencies
Country: Inglaterra
Editor: Pergamon-elsevier Science Ltd
Citation: Spectrochimica Acta Part A-molecular And Biomolecular Spectroscopy. Pergamon-elsevier Science Ltd, v. 81, n. 1, n. 135, n. 139, 2011.
Rights: fechado
Identifier DOI: 10.1016/j.saa.2011.05.073
Date Issue: 2011
Appears in Collections:Unicamp - Artigos e Outros Documentos

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