The kinetics and mechanism of the reaction between chlorine dioxide and phenol in acidic aqueous solution

Abstract

Chlorine dioxide reacts with phenol in aqueous solution below pH 2 appropriate to the rate law − d[C1O 2] dt ={k 1+k 2/H +}[ C1O 2][φOH] where k 1 = 0·47 ± 0·01 M −1 sec −1 and k 2 = 0·0110 ± 0·0002 sec −1 at 25°C and unit ionic strength. The corresponding activation parameters in the 5–35°C range are ΔH 1 ‡ = 11·6 ± 0·3 kcal mole −1, ΔH 2 ‡ = 13·5 ± 0·3 kcal mole −1, ΔS 1 ‡ = −21 ± 0·5 eu and ΔS 2 ‡ = −22 ± 1 eu. Additional evidence for a term in the rate law also containing ClO 2 − and suggesting Cl 2O 4 − as an oxidizing species was obtained. The mechanism of the reaction is discussed in terms of the observed rate law and a one-electron transfer process.