Voltammetric and Coulometric Studies of the Mechanism of Electrohydrodimerization of Diethyl Fumarate in Dimethylformamide Solutions

Abstract

The reduction of diethyl fumarate (DEF) in tetra‐n‐butylammonium iodide (TBAI)‐dimethylformamide (DMF) solutions at a platinum electrode has been studied by cyclic voltammetry, double potential step chronoamperometry, and controlled potential coulometry. The chronoamperometric response for several possible mechanisms of electrohydrodimerization has been obtained by digital simulation techniques, and a method for distinguishing among the mechanisms suggested. Results of double potential step chronoamperometric experiments strongly support a mechanism where the electrochemically generated anion radicals undergo a second‐order dimerization reaction. Controlled potential electrolysis results give evidence for a bulk polymerization reaction in the absence of proton donor; protonation in the presence of hydroquinones; and good efficiency to the hydrodimer product in the presence of lithium perchlorate trihydrate.

Dimerization of electrochemically generated ion radicals: mechanisms and reactivity factors

“…A first series of extended studies on the mechanism of the electrohydrodimerization of activated olefins in nonaqueous solvents, mainly dimethylformamide (DMF) and acetonitrile concluded that it involves the radical-radical coupling of two anion radicals (rr mechanism in Scheme 1) rather than the reaction of one anion radical on the starting olefin which would lead to a secondary anion radical that is further reduced at the electrode or in the solution (rs mechanism in Scheme 1) [34][35][36][37][38][39][40][41][42][43][44][45][46][47][48]. In all cases, small amounts of water were added to the solution to avoid the electron stoichiometry being less than one.…”

Effect of Sodium Ions on the Electrochemical Reduction of Diethyl Fumarate in Dimethylsulfoxide and Acetonitrile

“…b V vs. SRE; 0.050 V/sec. 1 This procedure is based on the fact that the boundary value problem comprising reactions [1]-151 is of the same form as that solved by Olmstead et al (13) when it is assumed that reaction [2] is fast and that the diffusion coefficients of the radical anion and ion pair are identical. The formulation treats the sum of the radical anion and ion pair concentrations as a new variable.…”

“…Childs et al (1) noted that the addition of sodium or lithium ions to the supporting electrolyte caused a substantial increase in the rate of dimerization of the radical anions of diethyl fumarate. Lithium also had the effect of decreasing the importance of polymerization side reactions as evidenced by an increase of the coulometric n-value to unity.…”

“…These data are consistent with a reaction scheme in which most of the radical anions exist as ion pairs, and the dimerization proceeds by reaction between these ion pairs (reaction [5]). In conclusion, it has been possible to correlate the data for the reduction of 1 in DMSO containing sodium to the mechanism given by reactions [1] - [5]. The ion pair formation constant and the three rate constants were evaluated.…”

A Life in Electrochemistry

“…And studies of these reactions led to an appreciation of their role in dimerization and polymerization (12). These eventually led to work demonstrating electronically conducting polymers.…”