Kinetics and Mechanism of the Oxidation of 2-Mercaptoethanol by Hydrogen Peroxide in Aqueous Solution

Article abstract of DOI:10.1021/j100270a029

The kinetics of oxidation of 2-mercaptoethanol by H2O2 to 2-hydroxethyl disulfide in aqueous solution has been studied.Over the pH range 9 to 13, the rate law for the oxidation of 2-mercaptoethanol was found to be where R is HOC2H4, K' is the apparent acid dissociation constant of H2O2, K'_a1 and K'_a2 are the apparent acid dissociation constants of HOC2H4SH and HOC2H4S^-, respectively, and a_H+ is the hydrogen ion activity.A nonlinear least-squares fit of experimental data to the above rate law gave values of k₁ = 12.64 +/- 0.54 M^-1 s^-1 and k₂ = 0.93 +/- 0.39 M^-1 s^-1 at 20 deg C.The rate law and other data indicate that the reaction proceeds via a nucleophilic displacement by thioethanol on hydrogen peroxide with the formation of HOCH2CH2SOH as a intermediate.