Electron Transfer Reaction of Theobromine and Permanganate Ion in Aqueous Acidic Media

Electron transfer reaction of theobromine (hereafter referred to as TB) and permanganate ion has been studied using spectrophotometric technique under pseudo first-order conditions at T = 24, [H+] = 3.2 × 10–1 mol dm–3and I = 1.0 mol dm–3 (Na2SO4). Stoichiometric study depicted that two moles of TB were consumed by one mole of permanganate ion. The rate of the reaction is first order in both [TB] and [MnO4-] and second order overall. It was observed that, [H+] and ionic strength respectively enhanced the rate of the reaction in the range studied. Michaelis-Mentens analysis showed no evidence of intermediate complex formation. Added anions and cations were observed to catalyze the reaction rate. The reaction conforms to the rate law as shown below:

-d [MnO4-]/dt = (a+b [H+]) [TB] [MnO4-]

where a = 0.041 dm3mol–1 s–1 and b= 0.028 dm3mol–1 s–1.

The reaction thus occurs by an outer-sphere pathway and plausible mechanism is proposed for the reaction.