Theoretical studies on the biocidal activity of phenylthiocyanates

Abstract

Molecular orbital calculations are reported on the structure and electronic properties of phenylthiocyanates using both the semi-empirical AM1 and MNDO methods and the ab initio 3-21G and 6-31G** methods. The fungicidal activity of these molecules which is thought to arise from their reaction with intracellular thiols does not appear to correlate with simple molecular properties such as the calculated atomic charges at the sulfur and cyano-carbon atoms. Reaction coordinate calculations at the AM1-SM1 level in water, using methanethiolate as the attacking nucleophile, strongly suggest that nucleophilic attack will occur at the cyano-carbon in preference to the sulfur atom, in line with experimental data obtained from the reactions of glutathione with 2-nitro-5-thiocyanatobenzoic acid in aqueous solution.