Proximity Effects in the Electron Impact Mass Spectra of 2-Substituted Benzazoles
dc.contributor.author | Chantler, Thomas | * |
dc.contributor.author | Perrin, Victoria L. | * |
dc.contributor.author | Donkor, Rachel E. | * |
dc.contributor.author | Cawthorne, Richard S. | * |
dc.contributor.author | Bowen, Richard D. | * |
dc.date.accessioned | 2009-02-09T10:06:58Z | |
dc.date.available | 2009-02-09T10:06:58Z | |
dc.date.issued | 2004 | |
dc.identifier.citation | Chantler T, Perrin VL, Donkor RE, Cawthorne RS and Bowen RD (2004) Proximity Effects in the Electron Impact Mass Spectra of 2-Substituted Benzazoles. International Journal of Mass Spectrometry. 236 (1-3): 65-80. Special issue: In honour of Dudley H. Williams. | |
dc.identifier.uri | http://hdl.handle.net/10454/2351 | |
dc.description | No | |
dc.description.abstract | The 70 eV electron impact mass spectra of a wide range of 2-substituted benzazoles are reported and discussed. Particular attention is paid to the mechanistic significance and analytical utility of [M–H]+ and [M–X]+ signals in the spectra of benzazoles in which the 2-substituent contains a terminal aryl group with one or more substituents, X. Loss of H or X occurs preferentially from an ortho-position from ionized 2-benzylbenzimidazoles, 2-phenethylbenzimidazoles, 2-styrylbenzimidazoles, 2-styrylbenzoxazoles and 2-styrylbenzothiazoles. In the three styrylbenzazole series, the [M–H]+ and/or [M–X]+ signals dominate the spectra. This unusually facile loss of H or X may be attributed to a proximity effect, in which cyclization of the ionized molecule is followed by elimination of an ortho-substituent to give an exceptionally stable polycyclic ion. Formation of a new five- or six-membered ring by the proximity effect occurs rapidly; cyclization to a seven-membered ring takes place rather less readily; but formation of a ring with only four atoms or more than seven atoms is not observed to a significant extent. The proximity effect competes effectively with loss of a methyl radical by simple cleavage of an ethyl, isopropyl and even a t-butyl group in the pendant aromatic ring of ionized 2-(4-alkylstyryl) benzazoles. | |
dc.language.iso | en | |
dc.subject | Benzimidazoles | |
dc.subject | Benzoxazoles | |
dc.subject | Benzothiazoles | |
dc.subject | Proximity effect | |
dc.subject | Rearrangement | |
dc.subject | Hydrogen atom elimination | |
dc.subject | Doubly-charged | |
dc.title | Proximity Effects in the Electron Impact Mass Spectra of 2-Substituted Benzazoles | |
dc.status.refereed | Yes | |
dc.type | Article | |
dc.type.version | No full-text in the repository | |
dc.identifier.doi | https://doi.org/10.1016/j.ijms.2004.05.012 | |
dc.openaccess.status | closedAccess |