Factors Influencing the Conformational Behavior on Sulfenyl Carbonyl XC(O)SY Compounds

ERBEN, M. F.; DELLA VÉDOVA, C. O.

Asian Chemistry Letters

Asian Chemical Society

Año: 2004 vol. 8 p. 219 - 229

The conformational properties of thioformic S-acid, HC(O)SH and its mono halogenated substituents XC(O)SH and HC(O)SY, with X, Y= F, Cl, Br were investigated by DFT calculations. Geometry optimizations and frequency calculations were performed at the B3LYP/aug-cc-pVTZ level of approximation. For the parent HC(O)SH compound, a good agreement was observed between the experimentally available data and the calculated ones. As in HC(O)SH, in the model XC(O)SH molecules the syn form (synperiplanar orientation of the C=O double bond with respect the S-H single bond) is preferred over the anti conformation (antiperiplanar orientation of the C=O double bond with respect the S-H single bond). Surprising, an inversion of syn/anti conformational stability was observed in the series of HC(O)SY compounds. Natural bond orbital (NBO) analyses that include deletion of delocalised orbital contributions reflect a complex interplaying of factors influencing the preferred conformation.