Electron impact studies: CXXXI—Ion cyclotron resonance studies of ambident nucleophiles. The reaction between the thioacetate anion and thioacetic anhydride. A further example of a negative ion McLafferty rearrangement

The [MeCOS]^? ion undergoes reaction with neutral thioacetic anhydride in an ion cyclotron resonance cell to yield an adduct [M+MeCOS]^? which decomposes principally by loss of CH₂CS, thus establishing the occurrence of nucleophilic attack through O at the carbonyl centre.