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Chemical ionization mass spectra of mononitroarenes
Author(s) -
Harrison Alex. G.,
Kallury R. Krishna Mohan Rao
Publication year - 1980
Publication title -
organic mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0030-493X
DOI - 10.1002/oms.1210150604
Subject(s) - substituent , chemistry , fragmentation (computing) , mass spectrum , protonation , nitrobenzene , chemical ionization , electron ionization , ionization , ion , mass spectrometry , medicinal chemistry , polyatomic ion , organic chemistry , chromatography , computer science , catalysis , operating system
The H 2 and CH 4 chemical ionization mass spectra of a selection of substituted nitrobenzenes have been determined. It is shown that reduction of the nitro group to the amine is favoured by high source temperatures and the presence of water in the ion source. The H 2 chemical ionization mass spectra are much more useful for distinguishing between isomeric compounds than the CH 4 CI mass spectra because of the more extensive fragmentation. For ortho substituents bearing a labile hydrogen abundant [MH H 2 O] + fragments are observed. When the substituent is electron‐releasing both ortho and para substituted nitrobenzenes show abundant [MHOH] + fragment ions while meta substituted compounds show abundant loss of NO and NO 2 from [MH] + . The latter fragmentation is interpreted in terms of protonation para to the substituent or ortho to the vitro function, while the first two fragmentation routes arise from protonation at the nitro group. When the substituent is electron‐attracting the chemical ionization mass spectra of isomers are very similar except for the H 2 O loss reaction for ortho compounds.