Please use this identifier to cite or link to this item: http://repositorio.unicamp.br/jspui/handle/REPOSIP/72114
Type: Artigo de periódico
Title: Spectroscopic and theoretical studies of some p-substituted alpha-methylthio-alpha-diethoxyphosphorylacetophenones
Author: Reis, AKCA
Olivato, PR
Zukerman-Schpector, J
Tormena, CF
Rittner, R
Domingues, NLC
Dal Colle, M
Abstract: The analysis of the IR carbonyl band of the cx-methylthio-alpha-diethoxyphosphoryl p-substituted acetophenones p-Y-Ph-C(O)CH [SMe][P(O)(OEt)(2)] (Y = OMe 1, H 2, F 3, Cl 4, Br 5 and NO2 6), supported by HF/6-31G** ab initio calculations of the (alpha-methylthio-alpha-diethoxyphosphoryl acetophenone 2, indicated the existence of a single stable cl conformer in gas phase and in solvents of increasing polarity, along with the presence of a second high energy conformation in gas phase. The cl conformer presents the (SMe) group in a syn-clinal (gauche) geometry and the [P(O)(OEt2)] group in a quasi-periplanar (quasi-cis) geometry with respect to the carbonyl group, which is stabilized by the synergism of the n(S)/pi*co and sigma(C-S)/pi*(CO) orbital interactions and O delta- ((PO)) center dot center dot center dot C delta+ ((CO)) orbital and Coulombic interactions, acting to increase the carbonyl oxygen negative charge, and in turn facilitates the O delta- ((CO)) center dot center dot center dot P delta+ ((PO)) electrostatic interaction. The negative and almost constant carbonyl frequency shifts (Delta v) of ca. -11 cm(-1) for compounds 1-6 relative to the parent acetophenones 7-12, in CCl4, corroborate the prevalence of the electronic interactions over the (-I-sigma) inductive effect of the alpha-substituents for the title compounds. The X-ray diffraction analysis for 3 indicates that it exists in the solid state in the c(1)(') conformation, which is stabilized by the intramolecular O delta-(1)([CO])center dot center dot center dot P delta+(5)([PO]) and H delta+(10)([SMe]) center dot center dot center dot O delta-(6)([PO]) orbital and electrostatic (hydrogen bond) interactions. Moreover, these molecules form dimers which are stabilized through intermolecular hydrogen bonds H delta+(4)([CH]) center dot center dot center dot O delta-(1)([CO]), H delta+(5)([Ph]) center dot center dot center dot O delta-(6)([PO]) and H delta+(6')([Ph]) center dot center dot center dot O delta-(6)([PO]). (c) 2006 Elsevier B.V. All rights reserved.
Subject: infrared spectroscopy
conformational analysis
Ab initio calculations
X-ray diffraction analysis
Country: Holanda
Editor: Elsevier Science Bv
Rights: fechado
Identifier DOI: 10.1016/j.molstruc.2006.03.054
Date Issue: 2006
Appears in Collections:Unicamp - Artigos e Outros Documentos

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