B. Pare, R. Vijay, S. Jonnalagadda
Feb 1, 2005
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Journal
Indian journal of chemistry. Sect. A: Inorganic, physical, theoretical & analytical
Abstract
The kinetics and mechanism of uncatalysed and Ru(III) catalyzed oxidative degradation of acridine orange {3,6-bis(dimethylamino)acridine zinc chloride double salt}(AO + ) by sodium chlorite in acidic medium has been investigated. With excess concentration of other reactants, both uncatalysed and catalyzed reactions follow pseudo-first order kinetics with respect to [AO + ]. The uncatalysed reaction follows fractional order kinetics in oxidant and first order kinetics in catalyst [Ru(III)]. Role of acid has been found to be complex. The rate coefficient of the uncatalysed reaction is 4.45×10 - 4 s - 1 while the catalytic constant for the catalyzed reaction is 8.00×10 - 4 s - 1 . Increase in ionic strength by the addition of neutral salt (Na 2 SO 4 ) resulted in decrease in rate constant value suggesting that oppositely charged species are involved in rate determining step. The effect of change in pH has also been reported. The overall stoichiometry of the reaction has been found to be 2AO + + 3ClO 2 - + 3H + + 6H 2 O = 2P + 2(CH 3 ) 2 N + OH + 2CH 3 CH 2 OH + 3HCl, where P is 7-aminoquinoline-2,3-dicarboxylic acid. The catalytic range for Ru(III) is found to be 1.0×10 - 8 mol dm - 3 . Ru(III) has been found to be complexed with chlorite. A mechanism consistent with the experimental results has been proposed.