Electron impact mass spectrometry of 2-(methoxycarbonylmethyl)-2-phenyl-1,3-benzoxathiole and 2-acetonyl-2-phenyl-1,3-benzoxathiole

The electron impact mass spectrometric behaviour of 2-(methoxycarbonylmethyl)-2-phenyl-1,3-benzoxa-thiole 3a and 2-acetonyl-2-phenyl-1,3-benzoxathiole 3b has been studied in detail. The structures of the more interesting fragment ions have been confirmed with the aid of accurate mass measurements, linked scans and collisional activation experiments. In addition to the ionic species already described in the general fragmentation pattern of 1,3-benzoxathiole derivatives, other fragments arising from the interaction of the carboxy-containing chain with the sulfur atom of these compounds have been observed and evidence presented.