Description
Demephion is an obsolete insecticide. Other than having a high aqueous solubility, very little data is available regarding its environmental fate or ecotoxicology. Demephion is an acetylcholinesterase inhibitor and a neurotoxin.
Production Methods
Demephion was manufactured as a mixture of two organophosphate isomers, demephion O (the oxon) and demephion S (the thiono), and commercial production followed the same processes used for other phosphorothioate/oxon pairs such as parathion and methyl parathion. Industrial synthesis began with preparation of the O,O diethyl phosphorochloridate or phosphorochloridothioate intermediate, generated by reacting phosphorus oxychloride or phosphorus thiochloride with ethanol under strictly anhydrous, acid scavenged conditions. In parallel, the dimethylamino substituted sulfide/oxide side chain was produced from the appropriate chloroalkyl precursor. Coupling of the amine derived fragment with the phosphorus intermediate occurred via nucleophilic substitution in aromatic or chlorinated solvents, with temperature control to manage hydrogen chloride evolution. The ratio of demephion O to demephion S depended on whether the phosphorus center was oxidised or thionated before or after coupling, and commercial material typically contained both isomers. After reaction completion, the mixture underwent neutralisation, phase separation, solvent exchange, and vacuum stripping to yield technical grade demephion.
