II in solvents, strong electron donors

Drastic acceleration of the oxidation of hexacyanoferrate(II) in solvents, strong electron donors 

Analogously to the dissociation of X in [Fe(CN)5(X)] , the oxidation of [FeCCN) ] to [Fe(CN)g] by O2 in aqueous-organic solvent mixtures depends drastically on the electron-donating abilities of solvents, the reaction in dimethyl sulfoxide and dimethylformamide being about 10 times faster than 

Oxidation rates depend very strongly on the solvent electron-donor ability. Oxidation is the fastest in DMSO, which is the best electron donor among those investigated [the rate acceleration factor 2x10 (relative to the rate in water where = 1.3x 10 s , at 35 °C, and at pH = 6.0), the electron-donor number, = 29.8, relative permittivity, = 48.9, at 20 °C], see Table 

The next largest rate acceleration is in DMF [acceleration factor 5x10, DNs Q = 27, Sj. = 36.7 (25 °C)]. The donor number of acetonitrile is 14.1, and the acceleration factor is only 160. The oxidation rates, as already mentioned, do not correlate with the relative permittivities of solvents. Thus, the relative permittivity of formamide is the highest of all solvents used (113.5 at 20 °C), but the acceleration factor is only 100. 

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