N-haloalkylthio compounds

Figure 13 Reaction of an active N-haloalkylthio compound with a SH group bearing cell component (nucleophile).

Microbicides belonging to this substance class are used on a large scale they include certain N-haloalkylthio compounds (Lucken, 1966) and isothiazolinone derivatives (Crow and Leonard, 1965 Lewis et al., 1971) [Figure 12.]. In principle there is no difference in the first step in the mechanism of action of N-haloalkylthio compounds and isothiazolone derivatives with activated N-S bonds both may react with SH groups found in cell components, with the N-S bond being split off and the formation of disulfides. 

For N-haloalkylthio compounds the course of the reaction is summarized in Figure 13. (Owens and Blaak, 1959). 

Figure 14 Formation of a N-haloalkylthio compounds containing an activated N-S bond.

In the meantime alternatives to TBTO have been developed which are getting more and more importance worth mentioning are N-haloalkylthio compounds e.g. 16.5. and 16.6., the 4-isothiazolin-3-one derivative 15.5., inhibitors of photo synthesis e.g. Diuron (10.9.) and triazine derivatives (e.g. 20.6.), tetrachloroisophtha-lodinitril (17.9.), dithiocarbamates e.g. Zineb (11.12.2.). 

Also haloalkylthio amides, e.g. Ar,A dimethyl-A/ -phenyl-A/ -dichlorofluoromethyl-thiosulphamide (Section 14.5) or A-triahalomethylthio-phthalimides (Sections 14.1 and 14.2) are well-known microbicides. They are electrophilic active agents with an activated N-S bond their role as an important class of microbicides is described separately in Section 14 (A -haloalkylthio compounds). 

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