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Electrochemical reductive cleavage of carbon-halogen bonds – application of Marcus theory in the analysis of nonlinear activation-driving force relationships

Arun Prasad Murthy

Abstract


A simple analytical expression for the current function has been formulated for reversible and irreversible processes in linear sweep voltammetry. The current function expression pertaining to the irreversible electron transfer reactions has been modified for the systems obeying Marcus-Hush kinetic law. The distinction between stepwise and concerted mechanisms has been delineated employing the current function analysis. A systematic way of distinguishing the mechanisms has been formulated employing Marcus-Hush model. The electrochemical reductive cleavage of the carbon-halogen bonds in 5-bromo-1,3-dichloro-2-iodobenzene have been analyzed so as to distinguish between the mechanistic dichotomy. The transition between the stepwise and concerted mechanisms has been demonstrated in 4′-bromomethylbiphenyl-2-carbonitrile. The electrochemical reductive cleavage of carbon-chlorine bond in 1-chloro-2,4-dinitrobenzene has been analyzed under EC mechanism. The reduction of carbon tetrachloride in various solvents follows a quadratic activation-driving force dynamics whereas the Butler-Volmer kinetics is observed in benzonitrile. A Hammett-type linear kinetic correlation pertaining to the cleavage of radical anions of aromatic halides has been formulated. The method of estimating standard potentials of irreversible electrode reactions has been demonstrated in the reduction of carbon-halogen bonds. The methodology for estimating Gibbs free energy of transfer of electrolytes from a reference solvent to the target solvent has been developed.

Keywords


Linear sweep voltammetry; Current function; Electrochemical reductive cleavage; Marcus theory; Convolution voltammetry;

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References


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ISSN 2347 – 8853

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