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Correlation analysis of reactivity in the oxidation of substituted benzaldehydes by pyridinium hydrobromide perbromide
Author(s) -
Aneja Meenakshi,
Kothari Seema,
Banerji Kalyan K.
Publication year - 2001
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.413
Subject(s) - chemistry , benzaldehyde , hydrobromide , pyridinium , reactivity (psychology) , bromide , medicinal chemistry , steric effects , solvent , benzoic acid , reaction rate , acetic acid , aqueous solution , organic chemistry , photochemistry , catalysis , medicine , alternative medicine , pathology
Abstract The oxidation of benzaldehyde and 35 monosubstituted benzaldehydes by pyridinium hydrobromide perbromide (PHPB) in aqueous acetic acid leads to the formation of the corresponding benzoic acids. The reaction is first order with respect to each of the benzaldehydes and PHPB. Addition of pyridinium bromide has no effect on the rate of oxidation. The oxidation of [ 2 H]benzaldehyde (PhCDO) indicated the presence of a substantial kinetic isotope effect. The effect of solvent composition indicated that the reaction rate increases with increase in the polarity of the solvent. The rates of oxidation of meta ‐ and para ‐substituted benzaldehydes were correlated in terms of Charton's triparametric LDR equation whereas those of ortho ‐substituted benzaldehydes were correlated with a tetraparametric LDRS equation. The oxidations of para ‐ and ortho ‐substituted benzaldehydes are more susceptible to the delocalization effect while the oxidation of meta ‐substituted compounds displays a greater dependence on the field effect. The positive value of η suggests the presence of an electron‐deficient reaction centre in the rate‐determining step. The reaction is subjected to steric hindrance by the ortho substituents. Copyright © 2001 John Wiley & Sons, Ltd.