ortho-methoxy-substituted diphenylmethyl cations



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Eur. J. Mass Spectrom. 5, 363 - 368 (1999)

Studies in organic mass spectrometry; Part 26. Unimolecular decomposition of ortho-methoxy-substituted diphenylmethyl cations

Maria Concetta Natoli
Dipartimento di Chimica Organica E. Paternò, viale Delle Scienze- Parco dOrleans, I-90128 Palermo, Italy
Leopoldo Ceraulo,* Mirella Ferrugia and Liliana Lamartina
Dipartimento di Chimica e Tecnologie Farmaceutiche, and Mass Spectrometry Network of South Italy, via Archirafi 32, I-90123 Palermo, Italy. E-mail:

ABSTRACT:
A double rearrangement (hydrogen migration followed by carboncarbon displacement) constitutes the main fragmentation process of the 2-methoxydiphenylmethyl cations formed by benzylic cleavage of the molecular ion of ortho-methoxy-substituted 1,1-diphenylalkanes with a wide range of internal energy. This has been demonstrated by recording mass analysed ion kinetic energy (MIKE) spectra, calculation of approximate activation energies (obtained by appearance energy difference) and calculation of a degrees-of-freedom effect. A geometry of the transition state, which accounts for the observed substituent effects, is proposed.

Keywords: electron ionisation, rearrangement process, mass analysed ion kinetic energy spectra, appearance energy, isotopic effect

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