STRUCTURE AND REACTIVITY OF ALIPHATIC DIAZO/COMPOUNDS .8. POLAROGRAPHIC OXIDATION OF SUBSTITUTED DIPHENYLDIAZOMETHANE AND RELATIONS WITH KINETICS OF THEIR SYNTHESIS WITH BENZOIC ACID

Diphenyldiazomethane and its substituted derivatives I (4-OCH3, 4-CH3, 4-Cl, 4-Br, 4-J, 4,4′-Br2, 4-CN and 4-NO2) undergo a reversible one-electron oxidation at a rotating platinum disk electrode in 0·1 M LiClO4/acetonitrile solution. The products of this electrode process are the radical cations II. A linear dependence was found between the polarographic half-wave potentials of the investigated compounds and the substituent constants σ or σ+. Based on the linear free energy relationship a general equation {A figure is presented} is given, including the correlation between the E 1 2-values and the rate constants of the decomposition of the diphenyldiazomethanes with benzoic acid. Such a linear relation can be formulated, because both the potential determining step of the electrochemical oxidation and the rate controlling proton transfer occurs at the diazo carbon, the position of the maximum electron density. © 1968.