Mass spectra of new heterocycles: XII. Main fragmentation pathways of the molecular ions of 5-methylsulfanyl-1-vinyl-1H-pyrrol-2-amines under electron impact and chemical ionization

Abstract

Fragmentation patterns of 5-methylsulfanyl-1-vinyl-1H-pyrrol-2-amines under electron impact (70 eV) and chemical ionization (methane as reactant gas) were studied for the first time. The electron impact mass spectra of all the examined compounds contained a strong peak of molecular ion which decomposed along four pathways. Two pathways involved cleavage of the C-S bonds with elimination of methyl (major) and MeS radicals (minor), and the two others, decomposition of the pyrrole ring. The chemical ionization mass spectra displayed strong molecular, [M + H]+, and odd-electron [M + H − SMe]+ ion peaks. N,N-Dimethyl-5-methylsulfanyl-4-phenyl-1-vinyl-1H-pyrrol-2-amine under chemical ionization with methane as reactant gas characteristically decomposed with formation of [M − C4H9N]+ as the only fragment ion.