Theoretical studies on the biocidal activity of 5-chloro-3-isothiazolone

The very high biocidal activity of 5-chloro-3-isothiazolone has been explored by calculating the structure and electronic properties of the tautomers which are thought to be produced in the cell by nucleophilic attack at the sulfur atom. The results obtained, both at the semi-empirical AM1/COSMO and PM3/SM3 levels and at the ab initio 4-31G level with polarisation functions on the sulfur and chlorine atoms, suggest that the high activity of this isothiazolone arises in part because of the preferential formation of a highly reactive thioacyl chloride following an initial reaction which cleaves the S-N bond of the isothiazolone ring. (C) 1998 Elsevier Science B.V.