Microdisk, single potential-step chronoamperometry, is applied to a range of organic substrates in the aprotic solvents tetrahydrofuran, propylene carbonate, acetonitrile and the room temperature ionic liquid [C 4 dmim][N(Tf) 2 ]. Fitting of the chronoamperometric transients was achieved using the Shoup and Szabo method [3]. Accurate values for the diffusion coefficients, D, and the number of electron(s) transferred, n, in the electrode process have been simultaneously and consistently obtained. This method is shown to be generally applicable and reliable for the determination of the number of electrons transferred in faradaic processes uncomplicated by relatively slow coupled homogeneous kinetics. Since the experiment is conducted essentially on typical voltammetric timescales it can be commended as a complementary technique for classical coulometry which is only possible on much longer timescales. The chronoamperometric method is therefore likely to be of greater relevance to the interpretation of voltammetric data.

Kinetic and thermodynamic (formal potential) data relating to the synthetically useful Li/Li+ couple in tetrahydrofuran (THF) solvent at a range of temperatures (196–295 K) are reported. Formal potentials, $E_{\rm f}^{\rm 0} $ have been measured versus the standard reference electrode, ${\rm Fc}\left( {4\,{\rm mM}} \right)/{\rm Fc}^ + {\rm PF}_6^ - \left( {4\,{\rm mM})} \right)$ in THF. At 295 K the following data have been obtained using a mathematical model to simulate the electro‐deposition (metal deposition and growth kinetics) processes of lithium (Li) on a platinum microelectrode; a $E_{\rm f}^0 $ of −3.48 ± 0.005 V, ${\rm d}E_{\rm f}^0 /{\rm d}T$ = −9.2 (±0.5) × 10−4 V K−1, the standard electrochemical rate constant, k0 = 1 (± 0.1) × 10−4 cm s−1, transfer coefficient, α = 0.57 ± 0.03 and diffusion coefficient, D = 8.7 ± 0.1 × 10−6 cm2 s−1. Copyright © 2007 John Wiley & Sons, Ltd.

Recent interest in the electrocatalytic activity of silver towards the reduction of alkyl iodides has led us to investigate whether the effect is observed in tetrahydrofuran (THF) at room temperature. Using platinum electrodes in THF for the reduction of alkyl halides at 298 K has been hampered by the solvent window, which 'obscures' the voltammetric signals of interest. In order to overcome these problems, voltammetry has been performed at low temperature and was shown to extend the voltammetric window, leading to accurate electrochemical analyses and even novel changes in mechanism(s) of the reactive species following electron-transfer (ET). Herein, it is shown that for a primary and tertiary alkyl iodide in THF, electroreduction at silver leads to a significant shift in the reduction potential to more positive values compared to platinum. In addition, following reduction, a characteristic series of oxidation peaks are observed and are shown to be due to the specific activity of iodide ions towards silver following reductive cleavage of the parent alkyl iodide. This characteristic feature is not observed with other halide ions: bromide and chloride. Preparative electrolyses at controlled-potential have suggested that the reduction of the above alkyl iodides is a one-electron concerted process. The 'free' iodide ions act as a monitor of reaction progression, and the carbon-centred radical either dimerises and/or abstracts a hydrogen atom from the electrolyte/solvent; 1-iodoadamantane giving percentage yields of 58% adamantane and 39% 1,1'-biadamantane, the primary alkyl iodide, prepared in-house, giving 67% R-H and 25% R-R.

A study of a range of aromatic molecules is investigated electrochemically to determine what makes an effective reducing mediator. With the aim of developing a better understanding of electron transfers (ETs) mediated from lithium in functional group reduction, a series of single ET reactions are reported in this paper. Typical reaction conditions involved the use of aromatic mediators such as naphthalene, anthracene, 4,4′‐di‐tert‐butyl‐1,1′‐biphenyl (DBB) with lithium metal in tetrahydrofuran (THF) at −78 °C. The results of these experiments showed that some mediators were more effective reducing reagents than others. Cryoelectrochemical procedures are used to mimic the conditions of the SET reactions in order to investigate the exact nature and role of the mediator formed upon ET. It is demonstrated that electro‐generated and stabilized radical anions of anthracene at −78 °C mediate the reduction of organic substrates, whereas the more reactive dianion is quickly protonated and therefore unable to act as an ET reagent; direct electrochemical reduction of the sulfide, phenyl 3‐phenylpropylsulfide (RSPh) gives the thiol, thiophenol, and propyl benzene whereas mediated reduction gives the dimer, diphenyl disulfide and propyl benzene. The possibility to selectively reduce a substrate with either a single electron or with two electrons is possible by using either the radical anion (mediated) or via the direct electroreduction. DBB and naphthalene (both single electron accepting species only) have been found to be the most effective reducing reagents in this study. Anthracene and other two‐electron accepting species only showed effective reducing ability when a stoichiometric amount of lithium was used therefore preventing the ‘over‐reduction’ to the dianion. Copyright © 2007 John Wiley & Sons, Ltd.

A synthetic method for conducting the acyloin reaction using electron transfer in solution is reported. By linking two esters via their oxygen atoms, it was possible to perform crossed acyloin reactions between two different ester functionalities and display a high degree of preference for an intramolecular coupling process.