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Mass spectrometric studies of some 4‐acyl substituted 1‐phenyl‐3‐methyl‐5‐pyrazolones
Author(s) -
Larsen Elfinn,
Qureshi Iqbal H.,
Møller Jørgen
Publication year - 1973
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.1210070114
Subject(s) - pyrazolones , chemistry , pyrazolone , cleavage (geology) , molecule , alkyl , mass spectrum , fragmentation (computing) , medicinal chemistry , alcohol , benzene , stereochemistry , mass spectrometry , organic chemistry , geotechnical engineering , chromatography , fracture (geology) , computer science , engineering , operating system
The electron‐impact‐induced fragmentation of 1‐phenyl‐3‐methyl‐5‐pyrazolone and six 4‐acyl substituted derivatives, have been studied with the aid of deuterium labelling, high resolution mass measurements and the metastable defocusing technique. The mass spectra of the pure keto and the pure enol forms do not show any significant differences. The predominant decomposition of the 4‐acyl substituted pyrazolones is the α‐cleavage with respect to the carbonyl group leading to intense peaks at m/e 201 by loss of the alkyl group. In the case of benzoyl and ethoxycarbonyl derivatives the α‐cleavage is associated with a specific hydrogen rearrangement causing the loss of a benzene and an ethyl alcohol molecule, respectively.