Redox kinetic studies of the reaction of nitrite ions and hexamethyl pararosalinine chloride in aqueous acidic medium: An approach to mechanism of reaction

Redox kinetics and mechanism of the reactions of hexamethylpararosalinine chloride (CV⁺) and NO₂⁻ were carried out in aqueous acidic medium, at temperature of 32.0 ± 1.0°C; ionic strength μ = 0.50 mol dm⁻³ (Na₂SO₄), [H⁺] = 5.0 x 10⁻³ mol dm⁻³ (H₂SO₄). The reaction showed a stoichiometry of 1:1, first order dependence in both [CV⁺] and [NO₂⁻], dependence on acid concentrations (in the acid range used), positive salt effect, evidence of intermediate complex formation and was not affected by added cations or anions Rate equation for the reaction has been proposed as: -d[CV⁺]/dt=(a[H⁺])[CV⁺][NO₂⁻]. The second order rate constant for the CV⁺ – NO₂ reaction was found to be 0.37 dm³ mol⁻¹ min⁻¹. Log k₁ versus 1/D gave negative slope for the reaction. Based on the results obtained experimentally, the inner – sphere mechanism is proposed for the CV⁺ – NO₂ reaction.