High resolution mass spectrometry. Part X. Loss of water from the molecular ions of aromatic amides

Abstract

Thermal loss of water by aromatic amides in the mass spectrometer is well known; it is now shown that when the amide group is flanked by both a methyl and a nitro-group elimination of water occurs by an electron-impact process. In view of the results of deuterium-labelling studies a mechanism is proposed for this loss in the case of 1-methyl-4-nitroimidazole-5-carboxamide. It is further shown that the resulting ion does not have the nitrile structure.