Molecular structure and properties of thioacetic acid

Abstract

Ab initio SCF-MO calculations have been carried out for thioacetic acid using the 3–21G and 4–31G basis sets. Energies and structures of several conformations of the two tautomeric forms of this molecule (the thiol and thion forms) determined by gradient geometry refinement are reported, and some conformationally dependent local geometry trends discussed. The results are compared with available data on acetic and dithioacetic acids in order to assess the effects of the substitution of oxygen by sulphur on molecular properties. It is shown that the O(H)→S(H) substitution originates important changes in the molecular properties, which can be correlated with the greater conjugating ability of the oxygen atom. On the other hand, the calculations indicate that the O=→S=substitution causes minor changes in the relative conformational energies, although other properties may be significantly affected. Charges on atoms, dipole moments and ionization potentials are also presented and compared with the available experimental values.