[Ethyl-1,2-H-3]Chlorpyrifos oxon and [ethyl-1,2-H-3]diazoxon were synthesiz
ed at a specific activity of 79 and 58 Ci/mmol, respectively, by catalytic
tritiation of the corresponding monovinyl analogs over Pd/C. The high speci
fic activity results from isotope exchange of the terminal vinylic protons
prior to saturation of the double bond. This radiosynthesis procedure is ap
plicable to the toxicologically-important oxon metabolites of many commerci
al O,O-diethyl phosphorothioate pesticides.