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Type: Artigo de periódico
Title: NMR and theoretical study of the (C=O)-N rotational barrier in the isomers cis- and trans-2-N,N-dimethylaminecyclohexyl 1-N,N '-dimethylcarbamate
Author: Basso, EA
Oliveira, PR
Wiectzycoski, F
Pontes, RM
Fiorin, BC
Abstract: Rotation around the conjugated C-N bond was investigated through dynamic NMR experiments, employing both H-1 and C-13 spectra, and theoretical calculations (HF and B3LYP with the 6-311 +G** and 6-31G** basis sets). Theoretical results predicted slightly distinct gas-phase rotational barriers for the isomers, although inclusion of solvation effects causes the barriers to be essentially equal. Experiments corroborate with this result. 1 H and 13C spectra provided somewhat different rate constants but the activation parameters (Delta S-double dagger, Delta H-double dagger and Delta G(double dagger)) are very similar for both. Additionally, we investigated the solvent effect through experiments in CDCl3, CD3OD, DMSO-d(6) and D2O solutions and SCRF calculations. The results agree with previous studies that the rotational barrier in carbamates is solvent insensitive. (c) 2005 Elsevier B.V. All rights reserved.
Subject: carbamates
rotational barriers
dynamic NMR
theoretical calculations
Country: Holanda
Editor: Elsevier Science Bv
Rights: fechado
Identifier DOI: 10.1016/j.molstruc.2005.06.001
Date Issue: 2005
Appears in Collections:Unicamp - Artigos e Outros Documentos

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