Decomposition of Strong Carboxylic Acids Redox Catalyzed By Carboxylate Ions; Chemical Grafting of Carbon Surfaces

Abstract

In mixtures of trichloroacetate ion and trichloroacetic acid in acetonitrile, trichloromethyl radicals are produced as a result of the redox reaction between the acid and its conjugated base. The reaction follows a loop mechanism in which the trichloroacetic acid is slowly consumed by proton reduction while the trichloroacetate ion is oxidized like in an electrochemical Kolbe reaction [1]. The hydroquinone-trichloroacetate complex was a good sensor of this unexpected self-decarboxylation redox reaction [2]. According to the conceptual framework of this reaction, the acid-base mixture was also tested but using the compounds derived from 4-nitrophenylacetic acid. The reaction ocurrs also in this system, however, when a glassy carbon electrode was present in the reaction solution, the grafting of nitrobenzyl groups on the surface was detected, whereas 4-nitrotoluene was detected as the product of a paralel reaction in solution. Therefore, the reaction represent an alternative to the covalent modification of carbon substrates without electrochemical induction.[1] Drochss P. Valencia, Pablo D. Astudillo, Annia Galano, Felipe J. González, Org. & Biomol. Chem., 2013, 11, 318-325 [2] Pablo D. Astudillo, Annia Galano, Jorge Tiburcio, Felipe J. González, J. Electroanal. Chem., 2007, 604, 57-64 Figure 1