O-(Methyl-d3) Phosphorodichloridothioic Acid Ester is an intermediate used in the synthesis of Chlorpyriphos-methyl-d6 (C425332), which is an isotope labelled Chlorpyriphos-methyl is an derivative of Chlorpyrifos (C425300), an insecticide that acts on the nervous system of insects by inhibiting acetylcholinesterase.