Pyrolyses and Mass Spectra of 2-Benzoxazolinone, 2-Benzimidazolinone, and 2-Benzothiazolinone

The electron-impact and chemical-ionization mass spectra of 2-benzoxazolinone (5), 2-benzimidazolinone (6), and 2-benzothiazolinone (7) have been compared with their pyrolysis products and parallels have been found. In each case, loss of CO occurs from [Formula: see text] followed by loss of CO for 5 and by HCN for 6 and 7. At 950° in a stream of N2, 5 gave 17% of C5H5N isomers, related to the loss of 2CO, along with 5.6% of quinoline. Compound 6 gave 14% of C6H4N2 isomers, related to the loss of CO. At 950°, 7 gave 2-thiophenecarbonitrile (1.1%), cyanonaphthalenes (4.5%), aniline (3%), cyanobenzene (2.5%), naphthalene (1.5%), and phenylisocyanate (2.5%). From 5–720–70% of the starting material was recovered or accounted for by isolation and identification of products in each case. G.c./m.s. was used to study pyrolysis mixtures.