The process for manufacturing dimethoate
(O,O-dimethyl S-methylcarbamoylmethyl
phosphorodithioate) 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, tetraoctylammonium bromide, tetraphenylphosphonium bromide, and
tetrabutylphosphonium bromide.