Chemical constitution and fungistatic action of organic sulphur compounds.

Elementary sulphur and some of its inorganic compounds have long been of practical importance for the control of parasitic and saprophytic fungi, but the use of organic compounds of sulphur is of more recent origin. Compounds such as tetramethylthiuram disulphide and certain metallic salts of dithiocarbamic acids are now of commercial importance in this connexion (Tisdale & Flenner, 1942; Roberts, 1942). This paper records observations made over some years on the relation of chemical constitution to fungistatic action in this and closely related classes of organic sulphur compounds. The fungicidal properties of the xanthic acid derivatives were first mentioned in the patent literature (Bohringer, 1929). The only recorded systematic investigation of homologous xanthates is that of Goldsworthy, Carter & Green (1942) where a series of cuprous salts was examined. The fungicidal properties of salts of dithiocarbamic acids and of their oxidation products, the thiuram sulphides, have been mentioned in the patent literature since 1931. Goldsworthy, Green & Smith (1942) examined metallic salts of three dialkyldithiocarbamic acids, but apart from this paper the few references in the scientific literature are to individual compounds, such as tetramethylthiuram disulphide, which have found commercial applications as fungicides. Limited investigations of the fungicidal activity of thiocyanates and isothiocyanates are recorded by Walker (1937), Wilcoxon & McCallan (1935) and Walker, Morell & Foster (1937). The first mention of the fungicidal properties of benzthiazole derivatives was in a patent (Graselli, 1932) which disclosed that the 1-hydroxy, 1-amino and 1-thiol derivatives were fungicides. The fungicidal activity of the 1-thiol and 1-phenyl derivatives was investigated by Everitt & Sullivan (1940).