O-Methyl O-(3,5,6-Trichloro-2-pyridinyl)phosphorochloridothioic Acid Ester-D3 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.