Stanley Wawzonek and the Introduction of Polar Aprotic Solvents into Organic Electrochemistry

The Observation of Dianions Generated by Electrochemical Reduction of trans-Stilbenes in Ionic Liquids at Room Temperature

“…The reversible and diffusion controlled nature of the process in eq was established from the linear dependence of peak height on concentration (1 to 15 mM), the linear dependence of peak height on the square root of the scan rate (0.05 to 1.0 V s –1 ), the unity ratio of the magnitude of reductive and oxidative peak currents, and by finding Δ E p = E p Ox – E p Red to be close to 0.06 V, after taking the Ohmic iR u drop into account. At more negative potentials, a chemically irreversible reduction process (Figure a) is detected consistent with coupling of the t -Stb •–/2– electron transfer and protonation reactions given in eqs and and also with data provided in other reports. − That is, no voltammetric evidence for the dianion is detected under these conditions. Rotating disk electrode (RDE) measurements (Figure S1) confirm that both reduction steps give the same limiting current per unit concentration values and hence involve the transfer of the same number of electrons, which in this case is equal to unity.…”

“…A very negative cathodic potential limit, significant electrochemical stability, along with the high hydrophobicity and hydridic nature of the cation of the (N 111 )(N 112 )BH 2 -NTf 2 ionic liquid should favor the registration of processes that require both very negative potentials and stabilization of the resulting products, particularly those that are strong bases and hence readily protonated. A paradigm of this type of process is electroreduction of trans -stilbene, which was chosen by Wawzonek to revolutionize electrochemical studies of organic compounds by pioneering the application of organic solvents such as acetonitrile and dimethylformamide (DMF) as an alternative to aqueous media in 1955. , An apt combination of sufficient polarity, good organic solvating power, and a sufficiently wide electrochemical window has made aprotic molecular solvents containing suitable electrolytes the medium of choice for numerous electrochemical studies for over 50 years. In the case of trans -stilbene, use of an aprotic solvent allowed detection of a fast and reversible one-electron reduction to yield the radical anion (reaction ).…”

“…A paradigm of this type of process is electroreduction of trans-stilbene, which was chosen by Wawzonek to revolutionize electrochemical studies of organic compounds by pioneering the application of organic solvents such as acetonitrile and dimethylformamide (DMF) as an alternative to aqueous media in 1955. 5,6 An apt combination of sufficient polarity, good organic solvating power, and a sufficiently wide electrochemical window has made aprotic molecular solvents containing suitable electrolytes the medium of choice for numerous electrochemical studies for over 50 years. In the case of trans-stilbene, use of an aprotic solvent allowed detection of a fast and reversible one-electron reduction to yield the radical anion (reaction 1).…”