Voltammetric Electro-synthesis of Catechol-Aspartic Acid Adduct at Different pHs and Concentrations

Electrochemical oxidation of catechol generates o-benzoquinone which acts as Michael acceptor and its reaction has been studied in the presence of different concentration of aspartic acid in aqueous solution with various pH values, different electrodes using cyclic voltammetry, controlled potential coulometry and differential pulse voltammetry. In this investigation aspartic acid behaves as a nucleophile and undergoes 1,4-Michael addition reaction with catechol. The participation of reaction of o-benzoquinone with aspartic acid at moderately higher concentration of nucleophiles in the second scan of potential was observed. The products synthesized from the reaction are assumed to be 2-((3,4-dioxocyclohexa-1,5-dien-1-yl)amino)succinic acid that undergo electron transfer at more negative potentials than the catechol’s. The effect of pH on catechol in presence of aspartic acid was studied by varying pH from 5 to 11. The concentration effect of nucleophiles with the fixed concentration of catechol (2 mM) was measured from 30 mM to 100 mM. The reaction was strongly influenced by the pH as well as concentration of aspartic acid. This nucleophilic addition reaction was mostly suitable in 70 mM of aspartic acid and 2 mM of catechol at pH 7. The behavior of the reaction was of ECE type followed by diffusion mechanism.