An Unexpected γ-Hydrogen Rearrangement in the Mass Spectra of Di-ortho-substituted Alkylbenzenes

Article abstract of DOI:10.1002/oms.1210230108

In contradiction of long-accepted mass spectrometric dogma, the site-specific γ-hydrogen rearrangement is observed in alkylbenzenes in which both ortho positions are blocked with methyl substituents.Mass spectrometric studies of a series of five trimethyl- and three tetramethylisopentylbenzenes have shown that this rearrangement is only suppressed to a significant degree in those compounds in which all three positions ortho and para to the isopenyl group are blocked.Deuterium labelling has confirmed the γ-site-specific origin of the migrating H atom while metastable studies have been used to investigate the mechanism of the rearrangement process.