Kinetics and Mechanism of the Chlorite-Thiourea Reaction in Acidic Medium

Article abstract of DOI:10.1021/j100193a039

The kinetics of the reaction between chlorite and thiourea in acidic medium have been studied.The stoichiometry of the reaction for pH > 3 is 2ClO2^- + SC(NH2)2 + H2O --> 2Cl^- + OC(NH2)2 + SO4^2- + 2H⁺; for pH < 3 OC(NH2)2 is hydrolyzed to NH4⁺ and CO2.The reaction is characterized by an induction period after which chlorine dioxide is produced.For ->/ < 2 the formation of chlorine dioxide is only transient.Thiourea is progressively oxidized to sulfonic acid before cleavage of the sulfur-carbon bond and formation of the sulfate.A 13-stepmechanism is proposed with rate-determining step ClO2^- + SC(NH2)2 + H⁺ --> HOCl + HOSC(NH)NH2.Computer simulation using this mechanism gives good agreement with experiment.