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Torsional profile of 2,2,2‐trifluoroethanol: A theoretical analysis with basis set extrapolation
Author(s) -
de Amorim Mauro B.
Publication year - 2008
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.21804
Subject(s) - extrapolation , basis set , conformational isomerism , chemistry , basis (linear algebra) , electronic correlation , computational chemistry , thermodynamics , crystallography , molecule , physics , density functional theory , geometry , mathematical analysis , mathematics , organic chemistry
Abstract The conformational potential for rotation around the CCOH torsional angle of 2,2,2‐trifluoroethanol (TFE) has been investigated at second‐order Möller–Plesset (MP2) perturbation theory with two series of Dunning's correlation consistent basis sets, cc‐pV N Z and aug‐cc‐pV N Z, N = D, T, Q, and 5. Single‐point energy calculations with MP4(SDQ)/(aug‐)cc‐pVTZ and MP4(SDQT)/cc‐pVTZ were also performed. It was found that the geometries of stationary points on this conformational profile are dependent on the basis set size, particularly the torsional angle of the gauche ‐isomer and the transition structure between the gauche‐ and anti‐isomers (from 61° and 142°, respectively, at cc‐pVDZ, to 65° and 149° at aug‐cc‐pVQZ), requiring at least a aug‐cc‐pVTZ basis set to be correctly optimized. Additionaly, an even lower barrier height (as low as 0.04 kcal/mol) than that previously calculated by Senent et al. for the conversion of anti‐TFE to its more stable (by about 1.95 kcal/mol) gauche‐conformer has been obtained, which reinforces the prediction that the main, if not the only, component of TFE in gas phase is its gauche‐isomer. The MP2 data were also used in different schemes of basis set extrapolation. Unfortunately, maybe because third‐order correlation energy contributions were not considered, these schemes have failed in providing suitable extrapolated energies. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008