Systox

Among other insecticides may be mentioned systox, first synthesized by Schrader. Ripper calls for caution in its use on food crops until more is known about the toxic metabohtes. 

The active constituent of this insecticide is stated to be 00 diethyl 0 -ethylmercaptoethyl phosphorothionate, 

Parathion (OO -diethyl 0 -p-nitrophenyl phosphorothionate) is known to isomerize to 0/S-diethyl O -p-nitrophenyl thiophos- 

A thorough examination of the whole problem was carried out by Gardner and Heath. Using diethyl phosphorochloridate containing P, they prepared compound (VIII) thus  

An infra-red spectrograph showed absorption in the wavelength band expected for P=S. 

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Styrene oxide Sulphate Sulphite Sulprofos Sulphur dioxide Sulphur hexafluoride Sulphuric acid Sulphuryl fluoride Systox... 

Rider JA, Moeller HC. 1964. Studies on the anticholinesterase effects of systox and methyl parathion in humans [Abstract], Fed Proc 23 176. 

Rider JA, Moeller HC, Puletti EJ, et al. 1969. Toxicity of parathion, systox, octamethyl pyrophosphoramide, and methyl parathion in man. Toxicol Appl Pharmacol 14 603-611. 

It was shown that systox indeed consisted of 00 diethyl (S-ethylmercaptoethyl phosphorothiolate (VIII) and OO -di-ethyl O -ethylmercaptoethyl phosphorothionate (VII). (Compound (IX) was not present, and in any case it does not seem to have been fully characterized.) It seems that at room temperature (VII) isomerizes to (VIII), the half-life being about 3 years. Furthermore, the P=S compound is much less effective than the P=0 compound as an insecticide. 

Just as O.M.P.A. is oxidized enzymically to a cholinesterase inhibitor of greatly enhanced activity (p. 173), so also are systox (p. 179), thimet and certain related sulphur organo-phosphorus compounds. 

March RB, Fukuto TR, Metcalf RL. 1957. Metabolism of p32-dithio-systox in the white mouse. m American cockroach. University of California, Citrus Experiment Station, Riverside, California MRID 83215. 

There is, however, one means of achieving the conflicting properties required for apoplastic transport without resort to compromise. This is by using precursors which have characteristics favouring uptake and are then converted within the plant to active toxicants which are more readily translocated. The principle is best illustrated by the long-established organophosphorus insecticides of the systox type such as demeton, disulfoton and phorate which are relatively lipophilic... 

Synonyms Mixture of 0,0-diethyl S-(and 0)-2-[(ethylthio)ethyl] phosphorothioates Mer-captofos Demox Systox... 

Demeton, or Systox, was one of the most interesting and challenging pesticides studied. Demeton consists of two isomers, Demeton-S and Demeton-0. The vapor pressures of both isomers are reported to be nearly the same. When gas chromatographed, the isomers are completely resolved and easily quantitated separately. 

Heath D. F., The Composition of Systox and the Behaviour of This Insecticide in the Living Plant, Pest Control Ltd., Cambridge, 1953. 

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