Kinetics and mechanism of oxidation of substituted benzaldehydes by 4-(dimethylamino)pyridinium chlorochromate

Abstract

Kinetics of oxidation of substituted benzaldehydes by 4-(dimethylamino)pyridinium chlorochromate (DMAPCC) in protic solvent system has been studied at 303 K. The product of oxidation has been identified as benzoic acid. A unit order dependence of the reaction with respect [DMAPCC] and [benzaldehyde] has been observed. The reaction has been found to be catalysed by H + ions. Decrease in the dielectric constant of the medium decreases the rate. To study the effect of structure reactivity relationships some para-substituted benzaldehydes were subjected to oxidation kinetics by DMAPCC at four different temperatures and thermodynamic parameters were calculated. The isokinetic plot and Exner plot shows that all the para-substituted benzaldehydes are oxidised by the same mechanism. The Hammett plot is linear with positive q value. From the observed kinetic results a suitable mechanism was proposed.

Studies on the Kinetics of Benzimidazolium Fluorochromate Oxidation of Pyridine-2-aldehyde in Aqueous Acetic Acid Medium

“…Kinetics of oxidation of benzaldehyde by various oxidizing agents have been well studied [3][4][5][6][7][8][9][10] . A search of literature revealed that only few reports are available for kinetics of oxidation of heterocyclic aldehydes [11][12][13][14][15][16] .…”

“…Exner suggested a method of testing the validity of isokinetic relationship 36 . The isokinetic relationship is tested by plotting the logarithms of rate constants at two different temperatures (T 2 > T 1 ) against each other according to Eq (4). log k (at T 2 ) = a + b log k (at T 1 ) (4) The linear relationship in Exner plots at 2 + log k 2 (313 K) and 2 + log k 2 (303 K) observed in the present study imply the validity of the isokinetic relationship 37,38 .…”

Kinetics and the mechanism of oxidation of methoxy benzaldehydes by benzimidazolium fluorochromate in an aqueous acetic acid medium

“…This reagent is more efficient and a stronger oxidizing agent. The oxidation kinetics of substituted benzaldehydes by various oxidizing agents have been extensively studied [11][12][13][14][15]. As a part of our continuing investigations of the oxidation of organic substrates by Cr(VI) [16][17][18][19][20], we report the kinetic features of the oxidation of benzaldehyde and various methoxy substituted benzaldehydes by BIFC in an aqueous acetic acid medium.…”

Kinetics and Mechanism of Oxidation of Aromatic Aldehydes by Imidazolium Dichromate in Aqueous Acetic Acid Medium

“…A number of new chromium(VI) containing compounds, with heterocyclic bases, like pyridinium chloro chromate(PCC) 2 , pyridinium bromo chromate (PBC) [3][4][5] , quinoliium chloro chromate(QCC) 6,7 , quinolinium fluoro chromate(QFC) 8 , quinolinium bromo chromate(QBC) 9 , imidazolium fluorochromate(IFC) 10 , pyridinium fluoro chromate (PFC) [11][12][13][14] , imidazolium dichromate(IDC) 15 and quinolinium dichromate(QDC) 16 have been developed to improve the selectivity of oxidation of organic compounds. The kinetics and mechanism of oxidation of aromatic aldehydes by various oxidants have been reported [17][18][19] . However, the kinetics of oxidation of substituted benzaldehydes by IDC, a Cr(VI) reagent has not yet been studied.…”