0,0-Dimethyl phosphorodithioic acid Malathion

The feed materials for malathion manufacture are 0,0-dimethyl phosphorodithioic acid and diethyl maleate or fumarate which react according to the equation ... 

At 87 °C and pH 2.5, malathion degraded in water to malathion a-monoacid and malathion P-monoacid. From the extrapolated acid degradation constant at 27 °C, the half-life was calculated to be >4 yr (Wolfe et al., 1977a). Under alkaline conditions (pH 8 and 27 °C), malathion degraded in water to malathion monoacid, diethyl fumarate, ethyl hydrogen fumarate, and QO-dimethyl phosphorodithioic acid. At pH 8, the reported half-lives at 0, 27, and 40 °C are 40 d, 36 h, and 1 h, respectively. However, under acidic conditions, it was reported that malathion degraded into diethyl thiomalate and 0,0-dimethyl phosphorothionic acid (Wolfe et al, 1977a). 

Diethyl mercaptosuccinic acid O.O-dimethyl phosphorodithioate. see Malathion Diethyl mercaptosuccinate. 0,0-dimethyl phosphorodithioate. see Malathion... 

Dimethyl phosphorodithioate, see Malathion 0,0-Dimethyl phosphorodithioate, see Dimethoate Dimethyl phosphorodithioic acid, see Dimethoate. Malathion... 

Dimethyl phosphorodithioic acid, see Malathion 0,0-Dimethyl phosphorophosphate, see Methoate Dimethyl phosphorothioate, see Malathion, Parathion 0,0-Dimethyl phosphorothioate, see Malathion 0,5-Dimethyl phosphorothioate, see Acephate Dimethyl phosphorothioic acid, see Dimethoate Dimethyl phosphorothionic acid, see Malathion 0,0-Dimethyl phosphorothionic acid, see Malathion Dimethyl sulfide, see Methyl mercaptan Dimethyl thiophosphate, see Malathion Dimethyl thiophosphoric acid, see Malathion Dimethyl triclopyr-aspartate, see Triclonvr Dimethyl triclopyr-glutamate, see Triclopvr... 

American Cyanamid in the early 1950s was therefore welcome. Malathion is widely used today. It is synthesized by condensing diethyl maleate with the 0,0-dimethyl phosphorodithioic acid obtained as previously discussed. 

In the 1970s, organophosphorus compounds became the leading type of insecticide. Over 40 such compounds have been registered in the United States as insecticides. The first organophosphorus insecticide was synthesized in 1938 and is known as tetraethyl pyrophosphate (TEPP). Another phosphate insecticide, Malathion is synthesized by condensing diethyl maleate with the o,o-dimethyl phosphorodithioic acid. 

Cassaday (1950), Shostakovski et al. (1951) and Melnikov et al. (1952) investigated extensively the addition reactions of dialkyl phosphorodithioic acids to unsaturated dicarbonic acid esters, and found that the dialkyl phosphorodithioic acids are added at the double bond in the same way as are mercaptans. This reaction was used by Cassaday (1950) who prepared 0,0-dimethyl-S-(l,2-dicarbethoxy)-ethyl phosphorodithioate by the addition reaction of dimethyl phosphorodithioic acid and maleic acid diethyl ester. This compound, known by the name malathion (89), became one of the most important phosphorus ester insecticides because of its low toxicity to warm-blooded animals. 

The technical production of malathion can be carried out in a single-step process without the intermediate preparation of dimethyl phosphorodithioic acid, starting from phosphorus pentasulfide, methanol and maleic acid diethyl ester (Matolcsy and Oswald, 1955 1957). 

Day (1991) reported that the hydrolysis prodncts are dependent upon pH. In basic solutions, malathion hydrolyzes to diethyl fumarate and dimethyl phosphorodithioic acid (Bender, 1969 Day, 1991). Dimethyl phosphorothionic acid and 2-mercaptodiethyl succinate formed in acidic solutions (Day, 1991). The hydrolysis half-hves of malathion in a sterile 1% ethanol/water solution at 25°C and pH valnes of 4.5, 6.0, 7.0 and 8.0, were 18, 5.8, 1.7 and 0.53 weeks, respectively (Chapman and Cole, 1982). The reported Itydrolysis half-lives at pH 7.4 at 20 and 37.5°C were 10.5 and 1.3 days, respectively. At 20°C and pH 6.1, the hydrolysis half-life is 120 days (Freed et al., 1979). Konrad et al. (1969) reported that after 7 days at pH values of 9.0 and 11.0, 25 and 100% of the malathion was hydrolyzed. Hydrolysis of malathion in acidic and alkahne (0.5 M sodium hydroxide) conditions gives (CH30)2P(S)Na and (CH30)2P(S)0H (Sittig, 1985). 

Malathion, the well-known insecticide, and the much more toxic isomalathion, (83) have one and two chiral centres, respectively. Chiral forms of the former have been prepared from the appropriate diethyl malate by sequential reaction with trifluoromethanesulphonic anhydride and sodium 0,0-dimethyl phosphorodithioate thus, for example, (-)-malic acid yields (/f )-malathion (84). Monodemethylation of the malathion enantiomers with strychnine, and methylation (dimethyl sulphate) of the... 

Dimethyl phosphorodithioate of diethyl mercaptosuccinate. See Malathion 0,0-Dimethyl phosphorothioate-0,0-diester with 4,4 -thiodiphenol. SeeTemephos Dimethyl phosphorous acid. See Dimethyl hydrogen phosphite... 

Synonyms S-(1-2,-Bis (carbethoxy) ethyl)-0,0-dimethyl dithiophosphate S-[1,2-Bis (ethoxycarbonyl) ethyl]-0,0-dimethyl phosphorodithioate S-1,2-Bis (Ethoxycarbonyl) ethyl-0,0-dimethyl thiophosphate Carbethoxy malathion S-(1,2-Dicarbethoxyethyl)-0,0-dimethyldithiophosphate Diethyl (dimethoxyphosphinothioylthio) butanedioate Diethyl mercaptosuccinate-0,0-dimethyl phosphorodithioate 0,0-Dimethyl-S-(1,2-dicarbethoxyethyl) dithiophosphate 0,0-Dimethyl phosphorodithioate of diethyl mercaptosuccinate Phosphorodithioic acid-0,0-dimethyl ester-S-ester with diethyl mercaptosuccinate Empirical C10H19O6PS2 Formula ... 

Phosphorodithioic acid-0,0-dimethyl ester-S-esterwith diethyl mercaptosuccinate. See Malathion... 

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