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Temperature‐dependent conformational analysis of cyclononane: An ab initio study
Author(s) -
Franco Mauro L.,
Ferreira Dalva E. C.,
Dos Santos Hélio F.,
De Almeida Wagner B.
Publication year - 2006
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.21135
Subject(s) - ab initio , chemistry , conformational isomerism , population , formalism (music) , gibbs free energy , thermodynamics , ab initio quantum chemistry methods , computational chemistry , nuclear magnetic resonance , physics , molecule , organic chemistry , art , musical , demography , sociology , visual arts
Quantum chemical methods were used for the theoretical determination of the conformational population for the relevant conformers of cyclononane, i.e., TBC, TCB, TCC, and M4 (or C1), which have been previously investigated experimentally through detailed examination of the nuclear magnetic resonance (NMR) spectrum. Our best Gibbs free energy result, evaluated with MP4(SDTQ)/6‐31G( d , p )//MP2/6‐31G( d , p ) energy differences and MP2/6‐31G( d , p ) thermal corrections, lead to a temperature‐dependent population in excellent agreement with the experimental results based on the analysis of the low temperature 13 C NMR spectrum. The nice agreement with experiment is achieved using MP2 harmonic frequencies for the evaluation of vibration partition functions within the standard statistic thermodynamics formalism. Theoretical temperature‐dependent infrared (IR) and 13 C NMR spectra were simulated and compared with experimental data, which confirmed the ab initio conformational population reported here. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007