Dimethyl fumarate, reductive dimerization

In an EC2j process, the initial ET step is followed by a second-order irreversible homogeneous reaction. For example, the feedback mode of SECM was employed to study the reductive hydrodimerization of the dimethyl fumarate (DF) radical anion [22]. The experiments were carried out in solutions containing either 5.15 or 11.5 mM DF and 0.1 M tetrabutylammonium tetrafluoroborate in A,A,-dimethyl form amide (DMF). The increase in the feedback current with increasing concentration of DF indicated that the homogeneous step involved in this process is not a first-order reaction. The analysis of the data based on the EC2 theory yielded the fc2 values of 180M-1 s-1 and 160M-1 s-1 for two different concentrations. Another second order reaction studied by the TG/SC mode was oxidative dimerization of 4-nitrophenolate (ArO-) in acetonitrile [23]. In this experiment, the tip was placed at a fixed distance from the substrate. The d value was determined from the positive feedback current of benzoquinone, which did not interfere with the reaction of interest. The dimerization rate constant of (1.2 0.3) x 108 M x s-1 was obtained for different concentrations of ArO-. 

One of the few mechanistic studies of mixed coupling reactions involves the reduction of dimethyl fumarate, or diethyl maleate, in the presence of the less easily reduced compounds 7 or cinnamon trile, [151]. In anhydrous DMF (BU4NI), the individual rate constants for dimerization of 52b and of 9 are known (110 and 880 M s respectively, (Tables 11 and 3) that is, 9 dimerizes faster than 52b by a factor of 8, and A 1/, = 0.41 V. With a twofold excess of 9 RRDE experiments at potentials where only 52b is reduced indicated that the normal RR homocoupling of 52b took place with a second-order rate constant identical to that measured in the absence of 9. RRDE experiments at a potential where both substrates are reduced revealed that electron transfer from 9 to unreduced 52b was the major reaction of [151]. No product studies were reported for... 

Reductive Dimerization of Dimethyl Fumarate and Fumaronitrile in N N-Dimethylformamide... 

The reductive hydrodimerization of activated olefins was considered as a good test system for initial SECM studies, due to the fact that the dimerization rate constant could be tuned via the substituent activating the olefinic double bond." " For the relatively slow dimerization of the dimethyl fumarate (DF) radical anion, a large UME (25 jam diameter Pt electrode) was employed so that the value of K2 (Equation 7.19) was in the range where the SECM response would be sensitive to the kinetics. Experiments were carried out with solutions of 5.15 and 11.5mM DF in dimethylformamide (DMF), containing 0.1 M tetrabutylammoniumtetrafluoroborate as a supporting electrolyte. The oxidation of -tetramethyl-l,4-phenylenediamine (TMPD), included in solutions at a con-... 

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