Spectrophotometric Study of Kinetics of Redox Reaction between Caffeine and Permanganate Ion in Aqueous Acidic Medium
Frank Jones
Department of Chemistry, Ahmadu Bello University, Zaria, Nigeria.
Idongesit Bassey Anweting *
Department of Chemistry, University of Uyo, Uyo, Nigeria.
Idongesit Edem Okon
Department of Chemistry, Ahmadu Bello University, Zaria, Nigeria and Transport Technology Centre, Nigerian Institute of Transport Technology, Zaria, Kaduna State, Nigeria.
Kenneth Edet Andem
Department of Marine Engineering, Maritime Academy of Nigeria, Oron, Akwa Ibom State, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
The kinetics of redox reaction between caffeine (hereafter referred to as CAF) and permanganate ion [MnO4-] has been studied spectrophotometrically in aqueous sulfuric acid medium. One mole of CAF was oxidized by one mole of [MnO4-].The reaction showed first-order kinetics with respect to both [CAF] and [MnO4-]. The investigation was carried out under pseudo-first order condition atI= 0.5 mol dm–3, (Na2SO4), T = 24± 0.1℃ and [H+] = 1.0 × 10–1mol dm-3. The reaction obeys the rate law: -d[MnO4-]/dt = (a+b [H+]) [CAF ] [MnO4-]. The reaction was retarded by increased in ionic strength of the reaction medium. The rate of the reaction showed dependence on acid (in the range used).Added anions and cations were observed to catalyze the reaction rate. Spectroscopic investigation and kinetic study did not suggest intermediate complex formation. An outer–sphere mechanism is proposed for the reaction.
Keywords: Redox reaction, caffeine, permanganate ion, spectrophotometric