Revisiting structure and conformational stability of ethanethiol

Abstract

Conformational analysis of ethanethiol molecule has been revisited using quantum chemical methods. The rotational barriers are calculated for the first time and they are found to be in good agreement with the experimentally measured rotational barrier reported in literature. Results pertaining to the thermodynamic parameters, normal modes of vibration, and rotational barriers are in good agreement with the previously reported experimental finding about the existence of two conformers. Furthermore, our calculations at the CCSD/CBS limit reveal that the gauche conformer is the most stable conformer with a higher relative abundance (49.82% & 64.07% corresponding to the dihedral angle HCCS and CCSH rotation parameter). The gauche conformer is 0.70 kcal/mol stable with respect to anti conformer. The rotational barriers around the C-C bond and C-S bond rotations calculated at the CCSD/cc-pVTZ level of theory are 1.42 kcal/mol and 3.62 kcal/mol respectively. NBO, Mulliken charges, and frontier molecular orbital calculations support these results very well.