STRUCTURE AND VIBRATIONAL FREQUENCIES OF THE MOLECULAR TRICHLOROMETHANESULFONIC ACID AND ITS ANION FROM AB-INITIO CALCULATIONS

The equilibrium structure, vibrational frequencies, and the infrared intensities of the trichloromethanesulfonic acid molecule and its anion have been investigated using the ab initio self-consistent Hartree-Fock method and second-order Moller-Plesset perturbation theory with the 6-31G** and lower basis sets. A normal mode analysis shows that, unlike CCl3 stretchings, the SO3 stretching vibrations in the CCl3SO3- anion are pure normal modes comprised of S-O stretching coordinates only. The molecular point group for the trichloromethanesulfonic acid molecule is C-1 and not C-s. The vibrational frequencies and the infrared intensities are sensitive to the basis set choice as well as to the electron correlation effects.