Electrochemical Oxidation Of Symmetrical Antioxidant Chicoric Acid In Dmso: Is This A Sequential Or A Simultaneous 2ece Mechanism?

Chicoric acid (ChA) is present in various plants, and it is known to have interesting biological properties, e. g., antioxidant activity. In this work, a detailed analysis of the electrochemical oxidation mechanism of L-(ChA) in DMSO on glassy carbon is reported, for the first time. Since geometry optimization of ChA using Density Functional Theory, confirms a C-2 symmetry, three mechanistic routes involving electron transfers (E) and deprotonation reactions (C) were proposed for the simulation work: 1) EECCEECC, 2) ECECECEC, and 3) two simultaneous 2(ECE) steps. Thermodynamic and kinetic parameters of the electrochemical and chemical steps were estimated by fitting the voltammetric simulation with the experimental voltammograms at different scan rates. Results showed that only the ECECECEC mechanism presented an adequate fitting with respect to experimental voltammograms. Homogeneous kinetic constants were close to a diffusion-limited process (ca. 1x10(10) M-1 s(-1), for bimolecular reactions) and equilibrium constants, within the range of 1.5-12.0.