Kinetics of alcohol oxidation by electrochemically generated superoxide ions in ionic liquids using double potential step chronoamperometry

Sethupathy K. Praneshwar, Inas Alnashef, Michael A. Matthews, John W. Weidner

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Double Potential Step Chronoamperometry (DPSC) was used to determine the rate constants for the homogeneous reactions of alcohols with the superoxide ion (O2•-) at different temperatures in two room temperature ionic liquids (RTILs). The technique was first tested by determining the pseudo first order rate constant for reduction of azobenzene to hydroazobenzene that, in turn, undergoes the benzidine rearrangement. Our results were in good agreement with values reported in the literature using DPSC and conventional kinetic methods. 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. The corresponding values of δS δH and δG for the reaction of superoxide ion with benzhydrol in [bdmim][HFP] calculated at T=45°C are -0.49 kJ/mole, 22.4 kJ/mole, and 177.9 kJ/mole, respectively. The second order rate constant for the oxidation of benzyl alcohol at 10°C in RTIL in [bmim][HFP] was determined to be =1.3 L mol-1 s-1. The pseudo first order rate constant for the homogeneous reaction of O2•- with different primary and secondary 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.

Original languageBritish English
Pages (from-to)672-688
Number of pages17
JournalAnalytical and Bioanalytical Electrochemistry
Volume5
Issue number6
StatePublished - Oct 2013

Keywords

  • Alcohol oxidation
  • Double potential chronoamperometry
  • Kinetics
  • Superoxide

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