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

Perumal Subramaniam, Natesan Thamil Selvi, Soundarapandian Sugirtha Devi
2014 Journal of the Korean Chemical Society  
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] and [Cr(VI)] at constant [H + ] and ionic strength. The reaction is acid catalysed, the order with respect to [H + ] is unity and the active oxidizing species is found to be HCrO3 + . The reaction mechanism involves the rate determining nucleophilic attack of sulfur atom of PSAA on chromium of
more » ... on chromium of HCrO3 + forming a sulfonium ion intermediate. The intermediate then undergoes α,β-cleavage leading to the liberation of CO2. 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.
doi:10.5012/jkcs.2014.58.1.17 fatcat:emlrif4rebczjoqimzriu47pnq