The electrochemical reduction of di-(2-ethylhexyl) phthalate (DEHP) in acetonitrile

Abstract

The redox behavior of the extensively utilized plasticizer and toxicant, di-(2-ethylhexyl) phthalate (DEHP), was studied in acetonitrile solutions using a combination of cyclic voltammetry (at varied scan rates, temperatures, and concentrations) and controlled potential electrolysis techniques. Overall, DEHP was found to be reducible by two one-electron steps at moderately large negative potentials to form a radical anion (Epred≈−2.47 vs. (Fc/Fc+)/V, where Epred=cathodic peak potential and Fc/Fc+=ferrocene/ferrocenium) and dianion (Epred≈−2.65 vs. (Fc/Fc+)/V), respectively. The results revealed that the cathodic reactions were only moderately chemically reversible, even when measured at high scan rates or lowered temperatures, as the reduced forms of DEHP were involved in several chemical transformations (dimerization and decomposition) following their generation. Based on the voltammetric and electrolytic responses gathered, a mechanism was proposed for the electrochemical reduction of DEHP, and the heterogeneous electron transfer and homogeneous reaction steps were modeled by digital simulations to determine the associated thermodynamic and kinetic parameters.