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Concerted chain isomerization in protonated alkylbenzenes
Author(s) -
Denhez J. P.,
Audier H. E.,
Berthomieu D.
Publication year - 1993
Publication title -
organic mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0030-493X
DOI - 10.1002/oms.1210280609
Subject(s) - alkylbenzenes , isomerization , chemistry , alkene , benzene , alkyl , protonation , photochemistry , medicinal chemistry , metastability , dissociation (chemistry) , cyclohexane , bond cleavage , ion , catalysis , organic chemistry
The first step in the unimolecular reaction of metastable protonated alkylbenzenes is the stretching of the C(benzene)—C(α) bond. Therefore, the intermediacy of a π‐complex [C 6 H 6 , alkyl + ] has often been proposed. In this work, the kinetic energy releases associated with the [ tert ‐alkyl] + product were measured for a large number of [C 6 H 6 –C n H 2 n +1 + ] ( n > 3) ions. At least for β‐branched alkylbenzenes, it is shown that the chain isomerization which occurs prior to dissociation involves neither the [C 6 H 6 , C n H 2 n +1 + ] π‐complex nor a [C 6 H 7 + , alkene] ion–neutral complex. The data are explained by a concerted process in which the stretching of the C(benzene)—C(α) bond is accompanied by the migration of the tertiary β‐hydrogen from C(β) to C(α).