Kinetics and Substituent Effect in the Oxidation of Aceto-phenones by Acid Iodate in Aqueous Methanol Medium

Department of Chemistry, University College, Kakatiya University, Warangal-506 009 Manuscript received 7 April 1982, revised 13 December 1982, accepted 23 April 1983 The kinetics of oxidation of acetophenone and substituted acetophenones by iodate in 50% (v/v) aq. methanol medium in presence of sulphuric acid has been investigated. The reaction is first order with respect to [acetophenone] and [iodate]. The oxidation process is catalysed by sulphuric acid and increase in the proportion of methanol in the reaction mixture enhances the rate. The order of reactivity observed among different acetophenones studied is H>p-OCH2 >p-CH2>p-Cl>m-CH3>m-OCH2>p-NO2> m-NO2. The plot of log kobs vs \(\sigma\)\(_p^+\). is linear, suggesting through conjugation between substituent and reaction centre. Activation parameters are evaluated and linearity of ΔH≠ vs ΔS≠ plot and Exners plot suggests the existence of isokinetic relationship. A probable mechanism involving rate limiting electrophilic attack of IO\(_2^+\) on methyl carbon atom of the acetophenone is proposed and the substituent effect is discussed