Structure reactivity in the oxidation of cyclic ketones by quinolinium dichromate

The kinetics of oxidation of cyclic ketones viz., cyclopentanone, cyclohexanone, cycloheptanone and cyclooctanone with quinolinium dichromate has been studied in 60 % acetic acid-water medium. The reaction shows first order dependence with respect to both oxidant and substrate. The reaction exhibits dual behaviour with respect to [H+] i.e., unit order dependence at lower [H+] and greater than one at higher [H+]. The rate of the reaction decreases with increase in the dielectric constant of the medium. The retardation of the rate by the addition of Mn2+ ions confirms that a two electron transfer process is involved in the reaction. A relationship has been observed between ring size and reactivity of the cyclic ketones. The order of reactivity has been rationalized.