Mass Spectrometry of Some Substituted 2-Benzylidenecyclohexanones and 2,6-bis-Benzylidenecyclohexanones

Abstract

The mass spectra of a series of some substituted 2-benzylidenecyclohexanones and a series of substituted 2,6-bis-benzylidenecyclohexanones have been determined at 70 eV. The major fragmentation pathways include an intramolecular aromatic substitution reaction leading to the loss of an ortho-substituent with the formation of a stable benzopyrylium ion, loss of carbon monoxide and ethylene from the parent ion and also further ions derived from subsequent cleavages of the cyclohexanone ring. The structural and electronic factors involved in the aromatic substitution reaction were examined by comparing the M – H/M and M – Cl/M ratios determined from the spectra of the various substrates.