Electrocarboxylation Reactions: Rotating Ring‐Disk Electrode, Voltammetric, and Electron Spin Resonance Studies of Dialkyl Fumarates and Maleates

Abstract

The reduction of the diactivated olefins dimethyl fumarate (DMeF), diethyl fumarate (DEF), di‐n‐butyl fumarate (DBF), dimethyl maleate (DMM), diethyl maleate (DEM), and di‐n‐butyl maleate (DBM), in N,N‐dimethylformamidetetra‐n‐butylammonium iodide solutions saturated with dissolved carbon dioxide at a platinum electrode has been studied by rotating ring‐disk electrode and cyclic voltammetry and in situ electron spin resonance spectroscopy. The results indicate that the rate‐determining step for each compound is the reaction of the radical anion with ; the radical anions are also involved in the dimerization and (for maleates) isomerization reactions which occur in the absence of . The coupling of the carboxylated radical to dimeric carboxylate is rapid. The rate constants for the reaction of the radical anions with were faster for maleates than for fumarates; pseudo‐first order rate constants for a saturated solution (ca. 0.2M) are DMeF, 1.5 sec−1; DEF, 0.47 sec−1; DBF, 0.35 sec−1; DMM, 32.0 sec−1; DEM, 19.4 sec−1; and DBM, 18.0 sec−1.