Premium
Mass spectrometry of cycloheptatriene derivatives—II: Ring contraction of the molecular ion of 7‐cyanocycloheptatriene. Participation of ring carbon in the loss of HCN (or HNC)
Author(s) -
Venema A.,
Nibbering N. M. M.,
De Boer Th. J.
Publication year - 1972
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.1210060607
Subject(s) - chemistry , ion , cycloheptatriene , polyatomic ion , ring (chemistry) , mass spectrometry , stereochemistry , organic chemistry , chromatography
At an electron energy of 70 eV (nominal) both the [M] + ·‐ion and the [MH] + ‐ion of the title compound expel hydrogen cyanide. 13 C labelling in the cyano group shows that these ions lose—within experimental error—only H 13 CN when decomposing in the ion source, i.e. when possessing a relatively high internal energy. In the first and second field free region, however, as well as in the ion source at low ionizing energies (9 eV, nominal), H 12 CN is also eliminated. This phenomenon may be explained by ring contraction of the molecular ion to a six membered ring, possibly initiated by the formation of a norcaradiene structure, which may then rearrange further to a species of higher symmetry. This ring contraction is supported by the occurrence of peaks of low intensity at m / e 78 and m / e 77, due to fragments which are generated in one step from the molecular ion.