The Behavior of 1-Phenyl-2-benzimidazolinethione and 1-Phenyl-2-benzimidazolinone upon Electron Impact and Pyrolysis

The mass spectra of 1-phenyl-2-benzimidazolinethione ( 3 ) and 1-phenyl-2-benzimidazolinone ( 4 ) have been compared with their pyrolysis products and similarities have been found. In the 70 eV mass spectrum of 3 , the base peak results from the loss of H*; at low ionizing voltages, this path and a competing path, loss of S, are the only ones which remain. At 650° in a stream of N 2 , 1-phenylbenzimidazole ( 8 , 20%) formed from the loss of S and benzimidazo-[2,1-b]benzothiazole ( 5 , 11%) formed by loss of H 2 . The major fragmentation paths in the mass spectrum of 4 are loss of CHO* and NCO*. At 950°, phenazine ( 6 , 35%) formed by loss of CH 2 O, and carbazole ( 7 , 14%) formed by loss of HNCO. In each pyrolysis, 65-70% of the starting material was recovered or accounted for.