Mechanistic studies of oxidation of substituted oxo acids by IFC in the presence of 1,10-phenanthroline
Department of Chemistry, Rajah Serfoji Government College (Autonomous), Thanjavur-613 005, Tamilnadu, India E-mail: prof.m.vellaisamy@gmail.com Manuscript received online 07 February 2019, revised 07 May 2019, accepted 16 May 2019 The catalytic activity of 1,10-phenanthroline (phen) in imidazolium fluorochromate (IFC) oxidation of 4-oxo-4-phenylbutanoic acid (4-oxo acids) has been studied in 50% acetic acid-50% water medium. The reaction is first order each in imidazolium fluorochromate, oxo acid and hydrogen ion concentration. The rate of the reaction has been conducted at five different temperatures. Thermodynamic parameters have been calculated. A good correlation is found to exist between log k 1(308 K) and Hammett constant (σ). For substituted oxoacids, the electron withdrawing substituents retard the reaction rate, while the electron releasing substituents enhance the rate of the reaction. The order of reactivities with substituents is p-CH3O > p-CH3 > p-C6 H5 > H > p-Cl > p-Br > m-NO2 is due to the presence of +I and –I effect. The Exner plot k2 (313 K) versus k2 (318 K) is linear and isokinetic temperature is obtained. This supports that all the reactions under this investigation follow a common mechanism. The constant ΔG values are obtained for all the substituted compounds. It also indicates that the substituted compounds are oxidized by same mechanism. Benzoic acid has been identified as the corresponding product of oxidation. Based on the kinetics results, a suitable mechanism has been proposed.
