1‐ und 2‐Elektronenschritte bei der Oxidation substituierter Paraphenylendiamine mit verschiedenen Oxidationsmitteln. II. Reaktionen mit Hexacyanoferrat

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Abstract
The oxidation kinetics of several N‐ and ring‐alkylated p‐phenylenediamines with hexacyanoferrate(III) (F3) was studied in the pH‐range 2,5 – 9 by means of a multimixing stopped flow technique which is described in detail. The p‐phenylene diamine‐derivatives (R) are oxidized via reversible one‐electron steps to the semiquinone diimine radical S (rate constants k1, k−1) and the quinone diimine T (rate constants k2, k−2). – k1 and k−1 could be measured directly for all compounds, k2 and k−2 for two derivatives. – Only the unprotonated species of R, S, T, F3 are reactive. The reduction is possible by the unprotonated Fe(CN)4‐6 (F2) and by its protonated form F2H. The complexes of F2 with alkali ions are inactive. In this way the respective association constants could be calculated. The kinetics of the reaction was compared with the thermodynamics, represented by potential‐pH‐diagrams. – The activation parameters of the reaction of p‐phenylene diamine‐derivatives with F3, F2 and also with iodine were measured. The activation energies of the second step (k2, k−2) are negligible. – Both oxidants attack the alkylated aminogroup of the p‐phenylene diamine derivatives. The radical cation is deprotonated before it is oxidized.