Mass spectra of 2H‐1,4‐benzoxazine and‐benzothiazine hydroxamic acids

Abstract

The mass spectra of various benzoxazine and benzothiazine hydroxamic acids and related lactams have been recorded and interpreted. Proposed fragmentations have been substantiated by means of deuterium-labeling and accurate mass measurements. Abundant molecular ions were observed in all spectra. The benzoxazine hydroxarnic acids fragmented initially by expelling an oxygen atom and a COOH radical from the molecular ion. The corresponding benzothiazine hydroxamic acids lost an oxygen atom and an OH radical, whereas their 1,l-dioxides decomposed by losing an oxygen atom and a ketene or substituted ketene molecule. The expulsion of CO, HCN, CS and SO, molecules, as well as alkyl and NO radicals were common subsequent fragmentations.