Mass spectral study of isomeric benzoxazolinones by electron ionisation

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Eur. J. Mass Spectrom. 3, 49 - 54 (1997)

Mass spectral study of isomeric benzoxazolinones by electron ionisation

S. Prabhakar, B.B. Gawali, U.T. Bhalerao and M. Vairamani^*
Indian Institute of Chemical Technology, Hyderabad - 500 007, India.

ABSTRACT:

The electron impact mass spectra of isomeric dihydrofurobenzoxazolinones, (13), hydroxy (2-methyl-2-propenyl)benzoxazolinones (45) and (2-methyl-2-propenyloxy)benzoxazolinones (67) are studied. The mass spectra of 13 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 proposed to explain the results. The mass spectra and collision-induced dissociation 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 fragmentation of 6 and 7 supports the proposition of dihydrofuran ring opening in 13. The fragmentation of 6 and 7 is different in comparison to 4 and 5, suggesting that 6 and 7 do not rearrange to 4and 5, respectively, either before or after ionisation.

Keywords: Isomeric benzoxazolinones, EI mass spectra, heteroatomeffect, comparison with solution phase.

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