Kinetics of the Reduction Reaction of Tetranitromethane by Thiosulfate Ion in the Absence and Presence of Copper(II) Ion in Aqueous Mixtures of Methanol and Ethanol

Abstract

Abstract The kinetics of the reduction reaction of tetranitromethane by the thiosulfate ion in the absence and presence of the copper(II) ion have been investigated in aqueous solution and aqueous mixtures of methanol and ethanol. The mechanism of reaction has been thought to be the following: C(NO2)4+S2O32−\xrightarrowk1C(NO2)3−+NO2+S2O3− Cu(II)+S2O32\xrightarrowk2Cu(I)+S2O3− C(NO2)4+Cu(I)\xrightarrowk3C(NO2)3−+NO2+Cu(II) 2S2O3−\xrightarrowrapidS4O62 The rate constants k1 and k2 have been determined under several conditions. The value of k1 was hardly affected by ionic strength, permittivity, and acetate ion concentration in the reaction solution, whereas k2 was markedly increased with decreasing ionic strength (μ), permittivity (D), and acetate ion concentration. For k2, plots of logk2 vs. μ1⁄2⁄(1+μ1⁄2 and logk2 vs. 1/D gave linear relationships. Under the specified conditions the k2-term in the reaction mechanism accounts for up to 90% of the reaction, the reaction being composed of a copper(II) catalyzed-chain reaction.