oa South African Journal of Chemistry - Nonlinear Kinetics and Mechanism of Nile Blue Reaction with Acidic Bromate and with Aqueous Bromine
Nile blue, a dye of the phenoxazine class follows complex kinetics during its reaction with bromate in acidic solutions. The reaction kinetics were investigated using photometric and potentiometric techniques and a stopped flow apparatus. Under excess acid and bromate concentration conditions, nile blue, (NB<sup>+</sup>) initially depletes very slowly. After an induction period, a swift reaction occurs. The overall reaction is NB<sup>+</sup> + BrO<sub>3</sub><sup>-</sup> react to P + CH<sub>3</sub>COOH + H<sup>+</sup> + Br<sup>-</sup>, where P is the de-ethylated N-oxide derivative of nile blue. The rapid kinetics of the reaction of bromine direct with nile blue were also reported. A 11-step mechanism, consistent with the overall reaction dynamics and supported by simulations, is described. The role of various bromo- and oxybromo- species is discussed.
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