Ab initio determination of the torsional spectra of acetic acid |
| |
Authors: | M. L. SENENT |
| |
Affiliation: | Departamento de Química y Física Teóricas , Instituto de Estructura de la Materia , CSIC, Serrano 113 bis, Madrid, E-28006, Spain |
| |
Abstract: | The torsional potential energy surface and the favourite geometries of acetic acid are determined with MP4/cc-p VTZ ab initio calculations. The molecule shows two planar trans and cis conformers whose energy difference is 1882.7 cm?1. Both minimum energy geometries are separated by a barrier of 4432.1 cm?1. The most stable trans-conformer shows a quite low methyl torsion barrier of 169.8 cm?1. The roto-torsional energy levels have been calculated up to J = 10. The two torsional fundamental frequencies of the trans-conformer, the methyl and the OH torsion are 82.857 (A2) and 77.050cm?1 (E) and 568.532 (A2) and 568.418cm?1 (E). The V3 barrier causes a splitting of 0.315cm?1 in the ground vibrational state where the quartic centrifugal distortion constants have been predicted to be DJ = 90.4kHz, DJK = ?301.5kHz and DK = 165.4kHz. Finally, the far-infrared spectra of two isotopomers have been simulated from ab initio calculations. |
| |
Keywords: | |
|
|