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Formation and identification of ionized and neutral cumulenes, RNCCCNH, by tandem mass spectrometry
Author(s) -
Flammang Robert,
Laurent Sophie,
FlammangBarbieux Monique,
Wentrup Curt
Publication year - 1993
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.1210281030
Subject(s) - chemistry , mass spectrometry , cumulene , isocyanic acid , tandem mass spectrometry , pyrolysis , analytical chemistry (journal) , molecule , ion , deuterium , organic chemistry , chromatography , physics , quantum mechanics
Using a combination of mass spectrometric techniques, it is shown that 5‐amino‐4‐cyanoisoxazole molecular ions (1 +˙ ), lose isocyanic acid HNO, not fulminic acid, HCN → O. Metastable ion fragmentations (unimolecular and collision induced) and deuterium‐labelling experiments are in agreement with the formation of a cumulenic structure, HNCCCNH (3a +˙ ). The hitherto unreported molecules HNCCCNH are also shown to be stable when formed in the low‐pressure gas phase of the mass spectrometer by using the technique of neutralization–reionization mass spectrometry. The arguments developed for the characterization of 3a +˙ have also been extended to the methylated and phenylated analogues 3b +˙ and 3c +˙ [RNCCCNH + ˙, R = CH 3 or C 6 H 5 ]. On flash‐vacuum pyrolysis at 700°C, 1 also loses HNCO producing the cumulene 3a, which is in turn readily tautomerized into malononitrile via wall collisions.