Abstract
The kinetics of the iodination of acetone, diethylketone and di-isopropylketone in aqueous media ([H 2SO 4] = 0·1 to 1·0 N; [I 2] a o = 10 −7 to 10 −5M) have been studied by couloamperometry under irreversible conditions. At these concentrations the rates of formation of the enol and of its iodination are similar. The general equation, which assumes the steady state approximation for the enol, is applicable, and is used to separate the rate constants of enolisation (k 1) and the apparent enol iodination rate constant (k II I 2 = K Ek 2 I 2 ). For acetone, the value given by Schwarzenbach for the enol equilibrium constant (K E = 2·5 x 10 −6) leads to an elementary rate constant for the addition of iodine to the enol (k 2 I 2 = 6·5 x 10 6 M −1s −1). This value is not, however, consistent with k I 2 = 1·5 x 10 8 M −1s −1, the rate constant for the iodination of the corresponding ether 2-ethoxypropene.
Published Version
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