Mass spectrometry of N-methylsulfonylureas. A re-examination

Some confusion has arisen in the literature regarding the electron impact mass spectrum of N-methyltolbutamide. The situation is complicated by the thermal lability of this compound which causes the formation of the corresponding N-methylsulfonamide. We present here spectral data at relatively low probe temperatures (and without an intervening gas chromatographic system) which we believe define the mass spectrum of N-methyltolbutamide more accurately than before. Similar data are presented for the analogous N-methylacetohexamide and show a rearrangement process for both substances not reported previously for this class of compounds.