Spectral and Mechanistic Investigation of Oxidative Decarboxylation of Phenylsulfinylacetic Acid by Cr(VI)

Abstract

ABSTRACT. The oxidative decarboxylation of phenylsulfinylacetic acid (PSAA) by Cr(VI) in 20% acetonitrile − 80% water (v/v) medium follows overall second order kinetics, first order each with respect to [PSAA] The product of the reaction is found to be methyl phenyl sulfone. The operation of substituent effect shows that PSAA containing electron-releasing groups in the meta-and para-positions accelerate the reaction rate while electron withdrawing groups retard the rate. An excellent correlation is found to exist between log k2 and Hammett σ constants with a negative value of reaction constant. The ρ value decreases with increase in temperature evidencing the high reactivity and low selectivity in the case of substituted PSAAs.

Dynamics of cetyltrimethylammonium bromide mediated reaction of phenylsulfinylacetic acid with Cr(VI): Treatment of pseudo-phase models

“…[H + ] = 0.50 mol dm -3 , [CTAB] = 5.0×10 -2 mol dm -3 , I = 0.65 mol dm -3 [PSAA] / 10 -2 mol dm -3 [Cr(VI)] / 10 -4 mol dm -3 k 1 / 10 centrations is contradictory with that of the reaction in the absence of micelles, where a negative effect with concentration of Cr(VI) was registerd. 23 The observed constancy of the k 1 values in the CTAB-mediated reaction indicates that dimer formation was prevented by the surfactant molecules.…”

“…This finding is in contradiction with the results observed in the reaction without micelles when a blue shift was observed in the absorption peaks of Cr(III). 23 It was assumed that in the absence of CTAB, Cr(III) formed a complex with the organic product, methyl phenyl sulfone. In a CTAB micellar medium, methyl phenyl sulfone may be solubilized deep in the micelle by hydrophobic interaction while the Cr(III) ion existed in the aqueous phase as the result of electrostatic repulsion.…”

“…Even though phenylsulfinylacetic acid (PSAA) shows a wide range of synthetic utility, no reports are available in the literature on the oxidation of PSAA except a few recent works. [22][23][24][25] Hence, this investigation of the redox reaction between PSAA and Cr(VI) in the presence of cationic surfactant cetyltrimethylammonium bromide (CTAB) is of great interest. The substituent and micellar effects are highlighted and the rate data in the presence of CTAB were subjected to Menger-Portnoy and Piszkiewicz kinetic pseudo-phase models.…”

A paradigm shift in rate determining step from single electron transfer between phenylsulfinylacetic acids and iron(III) polypyridyl complexes to nucleophilic attack of water to the produced sulfoxide radical cation: a non‐linear Hammett

“…As these intermediates are reported in most of the sulfoxidation reactions, and there is no systematic mechanistic study on the oxidation of phenylsulfinylacetic acid (PSAA) in the literature except our recent publications, [18][19][20][21] a systematic mechanistic investigation on the reaction between biologically active iron(III) polypyridyl complexes and therapeutically active PSAA is undertaken in the present work. On the basis of the observed spectral, kinetic, thermodynamic and substituent effects a suitable mechanistic path is proposed.…”

Picolinic acid promoted oxidative decarboxylation of phenylsulfinylacetic acid by Cr(VI)

“…Though phenylsulfinylacetic acid (PSAA) is a versatile compound finding utility in pharmaceutical and synthetic fields [20][21][22][23][24][25][26], literature survey clearly reveals that there is no systematic mechanistic study on the oxidation of PSAA except our recent publications [27][28][29][30][31]. Hence, in continuation of our work it is decided to carry out a systematic investigation on the PA promoted Cr(VI) reaction with PSAA with a view to proposing a suitable mechanistic path.…”