Fragmentation of 1-Alkyl Derivatives of 5- and 7-Nitro-2,1-Benzisothiazoline 2,2-Dioxides upon Electron Ionization

Fragmentation patterns upon electron ionization of some 1-alkyl-5-nitro- and 1-alkyl-7-nitro-2,1-benzisothiazoline 2,2-dioxides are described. It is observed that the molecular ions of the 7-nitro isomers undergo rearrangement reactions resulting in the loss of a molecule of the appropriate carbonyl compound and, concurrently, an acyl radical. Mechanisms for these reactions, which can be assumed to be an example of the “ortho-effect”, are proposed.