Kinetics of Alcohol Oxidation by Electrochemically Generated Superoxide Ions in Ionic Liquids Using Double Potential Step Chronoamperometry

Double potential step chronoamperometry (dpsc) was used to determine the rateconstants for the homogeneous reactions of alcohols with the superoxide ion (o2?-) atdifferent temperatures in two room temperature ionic liquids (rtils). the technique wasfirst tested by determining the pseudo first order rate constant for reduction of azobenzene tohydroazobenzene that, in turn, undergoes the benzidine rearrangement. our results were ingood agreement with values reported in the literature using dpsc and conventional kineticmethods. the activation energy for the oxidation of benzyl alcohol is 19.1 kj/mol in[bmim][hfp]; which is in good agreement with the value reported in the literature. thecorresponding values of s? ? , h? ? and g? ? for the reaction of superoxide ion withbenzhydrol in [bdmim][hfp] calculated at t=45?c are –0.49 kj/mole, 22.4 kj/mole, and177.9 kj/mole, respectively. the second order rate constant for the oxidation of benzylalcohol at 10?c in rtil in [bmim][hfp] was determined to be ?1.3 l mol-1 s-1. the pseudofirst order rate constant for the homogeneous reaction of o2?- with different primary andsecondary alcohols in 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][hfp]) and 1-butyl-2,3-dimethylimidazolium hexafluorophosphate [bdmim][hfp] at different temperatures was measured. the pseudo first order rate constant for the reaction of o2?- with benzhydrol in [bdmim][hfp] at t= 49, 57, 65, 84 c were found to be 60, 72, 92, 148 l mol-1 s-1. the pseudo first order rate constant for the reaction of o2?- with benzhydrol in [bmim][hfp] at t=27, 40 and 80 ?c were found to be 53,74, 201 l mol-1 s-1.the arrhenius plot was then used to determine the activation energy and pre-exponential factor for the corresponding reactions