Mechanism of the reaction between iodate and iodide ions in acid solutions(Dushman reaction)

Evidence is given for a stepwise mechanism in the Dushman reaction by using accelerated-flow mixing to measure reaction rates at high [H+] and [I-], w here pseudo-first-order rate constants vary from 213 to 6700 s(-1). The typ ical [H+](2) dependence is lowered due to the formation of appreciable [HIO 3]. The typical [I-](2) dependence is lowered because I2O2 is a steady-stat e intermediate, The rate expression is: -d[IO3](T)/dt = k(1)(k(2)/k(-1))K-H [H+](2)[I-](2)[IO3](T)/[(1 + K-H[H+])(1 + (k(2)/ k(-1))[I-])], where k(1) = 4.8 x 10(7) M-2 s(-1), k(2)/k(-1) = 2.3 M-1, and K-H = 2.5 M-1 at mu = 0.5 0 M, 25 degrees C.