Phosphorothiolates

This subclass contains a single bond, sulfur to the phosphorus atom. Phosphorothiolates are also called phosphorothioates by many authors they do not distinguish a thiono sulfur =S from a thiolo sulfur -S-. An example of this group is oxydemeton-methyl. Oxydemeton-methyl is a systemic and contact insecticide and acaricide for controlling aphids, leafhop-pers, mites, thrips, and other sucking insects on vegetables, ornamentals, and field crops. It has an oral LD50 in rats of 65-75 mg/kg. 

Pyraclofos is a contact and stomach poison insecticide effective against lepidopterous, coleopterous, and some hemipterous insects, mites, and nematodes in vegetables, fruit crops, and ornamentals. Its oral LD50 in rats is 237 mg/kg. 

---

The methylphosphonates differ from the phosphodiesters and phosphorothiolates in that the methyl derivatives are uncharged and are thus less water soluble. Moreover, compared to the naturally occurring phosphodiesters, the methylphosphonates form slightly less stable duplexes with complementary DNA and RNA sequences. This effect has been ascribed to the iaevitable chiraUty problem that is, if one isomer biads less well, the overall binding is decreased. Methylphosphonates can enter cell membranes by a passive mechanism and are completely resistant to nucleases. 

Haloisoxazolylureas have acardicidal and insecticidal properties 76JAP(K)7659858 and isoxazoles with a phosphorothiolate functionality are broad spectrum insecticides <80USP4212861, 78USP4104375, 78JAP(K)7825566>. 

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. 

Among phosphorus insecticides containing also nitrogen and sulphur we may mention 00 -diethyl-/S-/ -diethylaminoethyl phosphorothiolate (X). It was prepared (i) from diethyl phos-phorochloridate1 and sodium / -diethylaminoethyl mercaptide, (ii) from sodium diethyl phosphite and / -diethylaminoethyl thiocyanate, (iii) by the isomerization of OO -diethyl-O"-/ -diethylaminoethyl phosphorothionate (XI) obtained from / -diethylaminoethoxide and diethyl phosphorochloridothionate. 

DEDPI, and diethyl phosphorothiolate (DEPTh) in urine after dermal and possibly inhalation exposure to disulfoton (Brokopp et al. 1981). 

Exposure Levels in Humans. No data on disulfoton levels in various human tissues and body fluids of a control population, populations near hazardous waste sites, or occupationally exposed groups in the United States are available. The levels of disulfoton metabolites (DEP [0.05 ppm], DETP [0.04 ppm], DEPTh [0.008 ppm], dimethyl phosphate [0.04 ppm], dimethyl thiophosphate [0.180 ppm], and dimethyl phosphorothiolate [0.004 ppm]) in the urine of disulfoton formulators have been measured (Brokopp et al. 1981). Data on the levels of disulfoton and its metabolites in body tissues and fluids are needed to estimate the extent of exposure to disulfoton. 

Scheme 9 Phosphorothiolates from dialkyl- and diaryl phosphites. 

Dimethylethyl) -3- (methylthio) -1,2,4 -triazin-5 - (4 H) -one, see Metribuzin 7V,7V-Dimethylformamide, see Dimethylamine Dimethyl hydrogen phosphate, see Dichlorvos TV.O-Dimethylhydroxylamine, see Linuron 0,0-Dimethyl 5- (TV-hydroxymethylcarbamoyhnethyl) phosphorothioate, see Dimethoate 0,0-Dimethyl 5- (TV-hydroxymethylcarbamoyhnethyl) phosphorothiolate), see Dimethoate 0,0-Dimethyl 5- (A-methylcarbamoylmethyl) phosphorothiolate, see Dimethoate O, O-Dimethyl-0- (4- (methylthio) -m-tolyl) phosphate. 

CASRN 60-51-5 molecular formula C5H12NO3PS2 FW 229.30 Soil Duff and Menzer (1973) reported that in moist soils, dimethoate is converted to the oxygen analog, dimethoxon (0,0-dimethyl-5-(W-methylcarbamoylmethyl) phosphorothiolate) and two unidentified metabolites. The degradation rate of dimethoate in three different soils increased almost two-fold with a 10 °C increase in temperature (Kolbe et al., 1991). The reported half-lives of dimethoate in a humus-rich sandy soil, clay loam, and heavy clay soil at 10 and 20 °C were 15.3, 10.3, 15.5 d and 9.7, 4.8, 8.5 d, respectively. 

Scalfe, J.F. Protection of human red cell cholinesterase against inhibition by tabun and 0,O-diethyl-S-2-diethyl-aminoethyl phosphorothiolate. Can. J. Biochem. Physiol. 38 301-303, 1960. 

D,D-Diethyl-S-2-diethylaminoethyl phosphorothiolate [78-53-5] M 269.3, m 98-99". from isopropanol/ethyl ether. 

Diethyldithiocarbamic acid, AE9 >AE65 0,0-Diethyl 2-(ethylsulfinyl)-ethyl phosphorothiolate, A052 0,0-Diethyl 2-(ethylthio)ethyl phosphorothionate, A051 Diethyl fumarate, A007... 

---