Synthesis of high specific activity [ethyl-1, 2-H-3]-labeled chlorpyrifos oxon and diazoxon

[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.