MASS-SPECTRAL STUDY OF ISOMERIC BENZOXAZOLINONES BY ELECTRON IONIZATION

The electron impact mass spectra of isomeric dihydrofurobenzoxazolinon es, (1-3), hydroxy (2-methyl-2-propenyl)benzoxazolinones (4-5) and (2- methyl-2-propenyloxy)benzoxazolinones (6-7) are studied, The mass spec tra of 1-3 show differences in the relative abundance of an ion at m/z 163, A mechanism involving the heteroatom of the benzoxazolinone ring which is para to the oxygen of the dihydrofuran ring has been propose d to explain the results, The mass spectra and collision-induced disso ciation spectra of molecular ions of 4 and 5 are similar to those of 1 and 2, respectively, suggesting the rearrangement of 4 and 5 to 1 and 2, respectively, in the source of the mass spectrometer, The fragment ation of 6 and 7 supports the proposition of dihydrofuran ring opening in 1-3, The fragmentation of 6 and 7 is different in comparison to 4 and 5, suggesting that 6 and 7 do not rearrange to 4 and 5, respective ly, either before or after ionisation.