Analysis of C–F bond cleavages in methylfluorobenzoates—Fragmentation and dimerization of anion radicals using convolution potential sweep voltammetry

Electrosynthetic C–F bond cleavage

“…DFT calculations for both fluorobenzoate substrates indicated that the * orbital of the extended aromatic system is the initial electron acceptor, with the charge subsequently being transferred to the C-F σ* bond and resulting bond cleavage. 34 Electroreductive polymerization of polyhalogenated arenes with concomitant C-X bond cleavage was recently reported by Ekinci and co-workers. 37 In this reductive synthesis, polyaromatic compounds were formed on the surface of silicon or gold cathodes from polyhalogenated starting materials, including hexafluorobenzene, and were subsequently treated thermally to form graphene-like films.…”

“…22,33 An interesting case of a substrate-dependent mechanistic switch was reported by Muthukrishnan and Sangaranarayanan for electrochemical defluorination of fluorobenzoates (Figure 5, bottom). 34 Voltammetric studies of methyl-2-fluorobenzoate at high scan rates revealed a reversible electron transfer, indicative of a stable radical anion with decomposition to the corresponding aryl radical and fluoride being rate limiting. In contrast, methyl-4-fluorobenzoate was found to undergo electro-dimerization rather than hydrodefluorination.…”

“…For example, incorporation of fluorine in molecules can result in increased lipophilicity, bioavailability and metabolic stability. 1 Fluorine has the highest electronegativity of all elements in the periodic table 2 and forms highly polarized bonds with carbon, similar to Page 1 of 34 Organic & Biomolecular Chemistry 2 it heavier halogen congeners. However, the C-F bond is significantly stabilized by the electrostatic attraction between the positively polarized carbon and the negatively polarized fluoride.…”

Reductive dimerization mechanisms of some streptocyanine dyes

“…Note that in second order chemical reactions the response of the system can be expressed by the dimensionless parameter [23,26] = (RT/F)(k c • /r) with log ≥ 0.13 in the pure kinetic zone. Moreover, for kinetic control (high rate constant k ) of the overall process (reactions 1 and 2), the convolution potential sweep voltammetry method [27,28] shows that:…”

“…For reduction process governed by electron transfer (followed by fast dimerization), the apparent cathodic transfer coefficient˛a p could be evaluated from equations (12) and (13) [27], at 0.65 and 0.78 respectively.…”