Yield and Purity Comparison of Dimethoate Manufacturing Processes: Homogeneous Reaction, Two-Phase Uncatalyzed Reaction, and Phase Transfer Catalysis

摘要

The process for manufacturing dimethoate (O,O-dimethyl S-methylcarbamoylmethyl phosphoro-dithioate) should provide high yields of highly pure product which requires no further purification steps. A comparison of dimethoate yield and purity obtained by different manufacturing processes is presented. Ethanol, isopropanol, acetone, ethyl methyl ketone, and isobutyl methyl ketone were the solvents used when the reaction was carried out in one single homogeneous phase. In heterogeneous aqueous—organic solvent medium, an analysis by linear regression techniques has revealed temperature, reaction time, and organic solvent volume as the operational variables with statistical significance above 95% on the dimethoate purity, while only temperature was significant on gross and net yields. The phase transfer catalysis did not improve purity and yield obtained in heterogeneous solvent medium with any of the studied catalysts, namely methyltrioctylammonium chloride, tetrabutylammonium bromide, tetraoctyl-ammonium bromide, tetraphenylphosphonium bromide, and tetrabutylphosphonium bromide.