Subramaniam, Perumal and Selvi, Natesan Thamil (2015) Interaction of Pyridine-2,6-dicarboxylic Acid with Cr(VI) in the Oxidative Decarboxylation of Phenylsulfinyl Acetic Acid and Linear Free Energy Relationship. American Chemical Science Journal, 6 (2). pp. 105-114. ISSN 22490205
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Abstract
Aims: To investigate the catalytic activity of pyridine-2,6-dicarboxylic acid in the redox reaction of Cr(VI) and phenylsulfinyl acetic acid.
Study Design: The mechanism of the reaction was designed on the basis of the observed results of kinetic, spectral and substituent effect studies.
Place and Duration of Study: Laboratory of the Research Department of Chemistry, Aditanar College of Arts and Science, Tiruchendur, Tamil Nadu, India. September 2013 – January 2014.
Methodology: Phenylsulfinyl acetic acid and ten meta- and para-substituted phenylsulfinyl acetic acids essential for the present kinetic study were synthesized. The kinetic study was performed in 40% acetonitrile-60% H2O medium under pseudo-first-order conditions by maintaining [PSAA] >> [Cr(VI)] throughout the experiment. The progress of the reaction was monitored by following the rate of disappearance of Cr(VI) spectrophotometrically at 351 nm. The effect of pyridine-2,6-dicarboxylic acid on the rate of the reaction and the applicability of linear free energy relationship with different phenylsulfinyl acetic acids were tested.
Results: The reaction shows unit order dependence on Cr(VI) but follows Michalis-Menten kinetics with respect to substrate as well as catalyst. The order with respect to [H+] is between one and two. The thermodynamic parameters ∆‡S (-93.2 JK-1 mol-1) and ∆‡H (57.7 kJ mol-1) are evaluated respectively from the intercept and slope of the Eyring’s plot. The Hammett’s correlation affords a negative ρ value (-1.05).
Conclusion: Pyridine-2,6-dicarboxylic acid catalyzes the reaction and Cr(VI)-PDA complex is assumed to be the oxidizing species of the reaction. The sulfur of PSAA undergoes nucleophilic attack on Cr(VI)-PDA complex forming a ternary complex, Cr(VI)-PDA-PSAA which experiences decarboxylation, ligand coupling and further decomposition giving methylphenyl sulfone as the product. The mechanism with the associated reaction kinetics is assigned in support of substituent effect.
Item Type: | Article |
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Subjects: | AP Academic Press > Chemical Science |
Depositing User: | Unnamed user with email support@apacademicpress.com |
Date Deposited: | 01 Jul 2023 09:37 |
Last Modified: | 18 May 2024 07:42 |
URI: | http://info.openarchivespress.com/id/eprint/1476 |