Chlorine atom migration in the fragmentation of α-mesyl sulfonyl chlorides

The mass spectra of alkanesulfonyl chlorides can be rationalized by loss of a chlorine atom from the molecular ion, followed by loss of SO₂ with concomitant alkyl cation formation. The mass spectra of two α-mesyl sulfonyl chlorides exhibit a new fragmentation process in which the chlorine atom initially attached to sulfur migrates to the α-carbon atom with loss of SO₂, thereby resulting in retention of chlorine in the alkyl cation.