Studies of electrochemically generated reaction intermediates using modulated specular reflectance spectroscopy

Modulated specular reflectance spectroscopy was employed to identify reaction intermediates and to study the kinetics of their decay reactions. The solution-free anion radical CO[graphic omitted] was found to be the intermediate in the reduction of CO2 in aqueous solution and in a number of aprotic solvents. In the former case, the rate constant for protonation was found to be 5.5 1. mol–1 s–1. In aprotic systems, the mechanism for formation of oxalate involved coupling of CO[graphic omitted] with CO2 and not a dimerisation of the former, the rate constant being 7.5 × 103 l. mol–1 s–1. The decay reaction of the thianthrene cation radical generated anodically in acetonitrile containing controlled concentrations of water was found to be pseudo first order; possible mechanisms are discussed.