Synthesis of 2‐chloroethyl (13C)‐methyl sulfide

Abstract
Incorporation of a stable isotope‐labelled methylthio group into the mustard 2‐chloroethyl methyl sulfide 2 was complicated by concomitant reaction with iodide ion, a necessary byproduct from the precursor stable isotope‐labelled iodomethane. A two step procedure was therefore employed, initial displacement with mercaptoethanol 4 being followed by chlorination with thionyl chloride.