The kinetics of complex formation between Ti(IV) and hydrogen peroxide

The kinetics of the formation of the titanium-peroxide [TiO22+] complex from the reaction of Ti(IV)OSO4 with hydrogen peroxide and the hydrolysis of hydroxymethyl hydroperoxide (HMHP) were examined to determine whether Ti(IV)OSO4 could be used to distinguish between hydrogen peroxide and HMHP in mixed solutions. Stopped-flow analysis coupled to UV-vis spectroscopy was used to examine the reaction kinetics at various temperatures. The molar absorptivity (epsilon) of the [TiO22+] complex was found to be 679.5 +/- 20.8 L mol(-1) cm(-1) at 405 nm. The reaction between hydrogen peroxide and Ti(IV)OSO4 was first order with respect to both Ti(IV)OSO4 and H2O2 with a rate constant of 5.70 +/- 0.18 x 10(4) M-1 s(-1) at 25 degrees C, and an activation energy, E-a = 40.5 +/- 1.9 kJ mol(-1). The rate constant for the hydrolysis of HMHP was 4.3 x 10(-3) s(-1) at pH 8.5. Since the rate of complex formation between Ti(IV)OSO4 and hydrogen peroxide is much faster than the rate of hydrolysis of HMHP, the Ti(IV)OSO4 reaction coupled to time-dependent UV-vis spectroscopic measurements can be used to distinguish between hydrogen peroxide and HMHP in solution. (c) 2007 Wiley Periodicals, Inc.