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A highly correlated ab initio investigation of the temperature-dependent conformational analysis of cycloheptane

2005; Elsevier BV; Volume: 418; Issue: 4-6 Linguagem: Inglês

10.1016/j.cplett.2005.10.148

1873-4448

Cléber P. A. Anconi, Clébio S. Nascimento, Hélio F. Dos Santos, Wagner B. De Almeida,

Spectroscopy and Quantum Chemical Studies

The conformational analysis for the cycloheptane molecule has been carried out at the MP2/6-311G(d,p) and MP2/cc-pVDZ levels of theory, for structural parameters and harmonic frequency calculations, and using MP4(SDTQ) and CCSD(T) highly correlated methods for energy difference evaluation, aiming the determination of the temperature-dependent thermodynamic properties. The importance of using a separate treatment of the low frequency vibrational modes for the calculation of relative Gibbs free energy values is discussed and is shown to play a key role to bring the agreement of the theoretical conformational population predictions with the experimental gas phase reported value at 310 K.