malathion

95%tech, 57%ec,

Insecticide, acaricide

organophosphorus

NOMENCLATURE

Common name malathion (BSI, E-ISO, (m) F-ISO, ESA, BAN); maldison (Australia, New Zealand); malathon (JMAF); mercaptothion (South Africa); carbofos (USSR); no name (Germany); mercaptotion (Argentina)

IUPAC name diethyl (dimethoxythiophosphorylthio)succinate; S-1,2-bis(ethoxycarbonyl)ethyl O,O-dimethyl phosphorodithioate 

Chemical Abstracts name diethyl [(dimethoxyphosphinothioyl)thio]butanedioate 

CAS RN [121-75-5]  EEC no. 204-497-7  Development codes EI 4049 (Cyanamid)  Official codes OMS 1; ENT 17 034 

PHYSICAL CHEMISTRY

Composition Tech. grade is c. 95% pure.  Mol. wt. 330.3  M.f. C10H19O6PS2  Form Tech. is a clear, amber liquid.  M.p. 2.85 ºC  B.p. 156-157 ºC/0.7 mmHg.  V.p. 5.3 mPa (30 ºC)  KOW logP = 2.75  Henry 1.21 ´ 10-2 Pa m3 mol-1 (calc.)  S.g./density 1.23 (25 ºC)  Solubility In water 145 mg/l (25 ºC). Miscible with most organic solvents, e.g. alcohols, esters, ketones, ethers, aromatic hydrocarbons. Slightly soluble in petroleum ether and some types of mineral oil.  Stability Relatively stable in neutral, aqueous media. Decomposed by strong acids and by alkali; hydrolysis DT50 107 d (pH 5), 6 d (pH 7), 0.5 d (pH 9) (all 25 °C);  F.p. 163 °C (Pensky-Martens closed cup) 

APPLICATIONS

Biochemistry Cholinesterase inhibitor; proinsecticide, activated by metabolic oxidative desulfuration to the corresponding oxon.  Mode of action Non-systemic insecticide and acaricide with contact, stomach, and respiratory action.  Uses Used to control Coleoptera, Diptera, Hemiptera, Hymenoptera and Lepidoptera in a wide range of crops, including cotton, pome, soft and stone fruit, potatoes, rice and vegetables. Used extensively to control major arthropod disease vectors (Culicidae) in public health programmes, ectoparasites (Diptera, Acari, Mallophaga) of cattle, poultry, dogs and cats, human head and body lice (Anoplura), household insects (Diptera, Orthoptera), and for the protection of stored grain. Typical application rates for agricultural uses 0.5-1.25 kg/ha.  Phytotoxicity Non-phytotoxic in general, if used as recommended, but glasshouse cucurbits and beans, certain ornamentals, and some varieties of apple, pear, and grape may be injured.  Formulation types DP; EC; EW; UL; WP.  Compatibility Incompatible with alkaline materials (residual toxicity may be decreased).