Spectrophotometric Investigation of the Redox Reaction of Acid Green 1 with Periodate Ion in Aqueous Acid: Kinetics and Mechanistic Approach

Abstract

The redox reaction of acid green 1 (AG^3-) by periodate ion has been studied in aqueous acid at an ionic strength of I = 0.50 mol dm^-3 (NaCl), [H⁺] = 1.0 × 10^-4 mol dm^-3, T = 25 ± 1^oC and λ = 700 nm. The redox reaction displayed a stoichiometry of 2:1. The reaction showed a first-order dependence on [IO₄^-] and [AG^3-]. Investigation of the effect of ionic strength on the rate of the reaction showed that the rate of the reaction obeyed the positive Bronsted - Debye salt effect. This signified that the activated complex is composed of reactants of like charges. The rate of the reaction increases with an increase in hydrogen ion concentration in the range (0.1 – 4.0) × 10^-4mol dm^-3 investigated. The addition of acrylonitrile to a partially reacted mixture in the presence of excess methanol did not lead to gel formation. This shows that the participation of free radicals in this reaction is unlikely. Based on the results obtained, the reaction probably obeyed the outer-sphere reaction mechanism.