82453-66-5Relevant academic research and scientific papers
RELATIVE MIGRATORY APTITUDE OF PARA- AND META-SUBSTITUTED PHENYL GROUPS DURING 1,2-SHIFT IN 1-ARYL-1,3,4,5,6-PENTAMETHYL-2-HYDROXYBENZENONIUM IONS
Berezina, R. N.,Ugryumova, L. E.,Korchagina, D. V.,Shubin, V. G.
, p. 516 - 525 (2007/10/02)
The kinetics of the rearrangement of 1-X-phenyl-1,3,4,5,6-pentamethyl-2-hydroxybenzenonium ions (III) to 1-X-phenyl-1,2,3,5,6-pentamethyl-4-hydroxybenzenonium ions (IV) (X = p-CH3, p-OCH3, p-Cl, m-CF3, p-CF3) were studied by the PMR method.The rates of this nondegenerate rearrangement are significantly lower than the rates of the degenerate rearrangements of 1-X-phenyl-1,2,3,4,5,6-hexamethylbenzenonium ions, and this is evidently due to the endothermic character of the controlling stage of 1,2-shift of the aryl group in the ion (III) and by the increase in the "internal" barrier to the 1,2-shift.The logarithms of the rate constants for the 1,2-shift of the aryl groups in the ions (III) are related to the ?+ constants of the substituents X by a linear correlation, and the angular coefficient (ρ) is fairly close to values typical of the degenerate rearrangements of 1-X-phenylhexamethylbenzenonium and 9-X-phenyl-9,10-dimethylphenanthrenonium ions.This indicates that the series of the relative migratory aptitudes in the meta- and para-substituted phenyl groups has little sensitivity to change in the ?-electron deficiency at the carbonium center of the arenonium ions.
