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Type: Artigo de periódico
Title: Concentration and solvent effects on the conformational equilibrium of cis-3-ethoxycyclohexanol by H-1 NMR and IR spectroscopy
Author: de Oliveira, PR
Ortiz, DS
Rittner, R
Abstract: NMR data, in CCl4, show that an increase in the concentration of cis-3-ethoxycyclohexanol (cis-3-ECH) shifts the conformational equilibrium from the ax-ax conformer (Xax-ax = 51 % at 0.01 mol L-1), stabilized by an intramolecular hydrogen bond (IAHB), to the eq-eq conformer (Xeq-eq = 67% at 0.40 mol L-1), which forms intermolecular hydrogen bonds (IEHB), as confirmed by IR data. The Delta v values, obtained by IR spectra, indicated that cis-3-ECH presents a stronger IAHB than the cis-3-methoxycyclohexanol, due to the increase in substituent steric and group electronegativity effects. The percentage of eq-eq conformer also increases with the solvent basicity, from 5 1 % (Delta G(eqeq-axax) = - 0.03 kcal mol(-1) in CCl4 to 97% (Delta G(eqeq)-(axax) = -2.05 kcal mol(-1)) in DMSO. Values of 4.58 and 5.39 kcal mol for the IAHB strength in cis-3-ECH, were obtained from the theoretical data at CBS-4M and B3LYP/6-311 + G** levels, respectively. (c) 2005 Elsevier B.V. All rights reserved.
Subject: conformational analysis
intramolecular hydrogen bond
NMR spectroscopy
IR spectroscopy
theoretical calculations
Country: Holanda
Editor: Elsevier Science Bv
Rights: fechado
Identifier DOI: 10.1016/j.molstruc.2005.11.009
Date Issue: 2006
Appears in Collections:Unicamp - Artigos e Outros Documentos

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