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Type: Artigo de periódico
Title: The Relevant Effect Of An Intramolecular Hydrogen Bond On The Conformational Equilibrium Of Cis-3-methoxycyclohexanol Compared To Trans-3-methoxycyclohexanol And Cis-1,3-dimethoxycyclohexane.
Author: de Oliveira, Paulo R
Rittner, Roberto
Abstract: 1H NMR data show that an increase in the concentration of cis-3-methoxycyclohexanol (cis-3-MCH) shifts the conformational equilibrium from the 1aa conformer, stabilized by an intramolecular hydrogen bond (IAHB), to the 1ee conformer [X(ee) = 44% (at 0.05 molL(-1)) to 59% (at 0.40 molL(-1)), in CCl4], which forms intermolecular hydrogen bonds (IEHB), as confirmed by IR data. The percentage of 1ee conformer increases with the solvent polarity, from 33% (DeltaG(ee-aa) = 1.72 kJmol(-1)) in cyclohexane (C6D12) to 97% (DeltaG(ee-aa) = -8.41 kJmol(-1)) in DMSO. For trans-3-methoxycyclohexanol (trans-3-MCH), 1ae and 1ea conformers are almost equally present in the studied solvents, 1ae increasing from 41%, in C6D12 (DeltaG(ae-ea) = 0.84 kJmol(-1)), to 49%, in DMSO (DeltaG(ae-ea) = 0.13 kJmol(-1)). A value of 18.4 kJmol(-1) for the strength of IAHB in cis-3-MCH was obtained, from the theoretical data, through the CBS-4M method.
Subject: Cyclohexanes
Hot Temperature
Hydrogen Bonding
Magnetic Resonance Spectroscopy
Models, Chemical
Molecular Conformation
Molecular Structure
Peptides, Cyclic
Rights: fechado
Identifier DOI: 10.1016/j.saa.2004.07.004
Date Issue: 2005
Appears in Collections:Artigos e Materiais de Revistas Científicas - Unicamp

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