Differentiation of ionised benzimidazole from its isomeric α-distonic ion by collision-induced dissociation and neutralisation

Eur. J. Mass Spectrom. 11, 381–387 (2005)
DOI: 10.1255/ejms.775

Differentiation of ionised benzimidazole from its isomeric α-distonic ion by collision-induced dissociation and neutralisation–reionisation mass spectrometry

Thanasis Karapanayiotis^a and Richard D. Bowen^*
Chemical and Forensic Sciences, School of Life Sciences, University of Bradford, Bradford, West Yorkshire BD7 1DP. E-mail: r.d.bowen@bradford.ac.uk

ABSTRACT:

Ionised benzimidazole and its isomeric α-distonic ion (or ionised ylid) have been examined by recording their metastable ion, collision-induced dissociation and neutralisation–reionisation mass spectra. These tautomers may be distinguished by careful consideration of key features of the collision-induced dissociation spectra, with or without prior neutralisation and reionisation. Formation of doubly-charged ions by charge stripping occurs preferentially when the α-distonic ion is subjected to collision. This α-distonic ion survives neutralisation and reionisation, thus establishing that the corresponding ylid is stable on the microsecond time frame. The effects of benzannulation on the ease of differentiation of classical and distonic radical cations derived from biologically important heterocycles are considered.

Keywords: benzimidazole, ylid, radical-cation, distonic ion, isomerisation, tautomerism

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