PHOTOLYSIS OF DIMEPIPERATE IN AQUEOUS-SOLUTION

Dimepiperate, S-(1-methyl-1-phenylethyl) piperidine-1-carbothioate (I) was degraded in aqueous solution by ultraviolet irradiation into piperidine (II), alpha-methylstyrene (III), acetophenone (IV), and formaldehyde (V). The reaction followed first-order kinetics. In sunlight the reaction occurred only in the presence of a sensitiser and afforded the same four photolytic degradation products. In the absence of oxygen the herbicide was converted much more rapidly, but yielded only (II) and (III) as products. A mechanism which accounts for the formation of the photoproducts is proposed.