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Formation and identification of ionized and neutral cumulenes, RNCCCNH, by tandem mass spectrometry

✍ Scribed by Robert Flammang; Sophie Laurent; Monique Flammang-Barbieux; Curt Wentrup

Book ID: 102560332
Publisher: John Wiley and Sons
Year: 1993
Tongue: English
Weight: 423 KB
Volume: 28
Category: Article
ISSN: 1076-5174
DOI: 10.1002/oms.1210281030

No coin nor oath required. For personal study only.

✦ Synopsis

Using a combination of mass spectrometric techniques, it is shown that 5-amino-4-cyanoisoxazole molecular ions (I+'), lose isocyanic acid HNC=O, not fulminic acid, HCGN + 0. Metastable ion fragmentations (unimolecular and collision induced) and deuterium-labelling experiments are in agreement with the formation of a cumulenic structure, HN=C=C=C=NH (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+' [ RN=C=C=C=NH+', R = Cfi, or C,H,I. On flash-vacuum pyrolysis at 7OO0C, 1 also loses HN=C=O producing the cumulene 3a, which is in turn readily tautomerized into malononitrile via wall collisions.

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