Kinetics of the reaction of para-substituted nitrosobenzenes with methoxide ion in methanol

Abstract

The kinetics of the reaction of RC₆H₄NO with MeO^– to yield RC₆H₄NN(O)C₆H₄R (R = H, p-NMe₂, p-OMe, or p-Cl), or RC₆H₄NO₂ in the presence of oxygen (R = H, p-OMe, or p-Cl) were studied as a function of temperature and MeO^– concentration. ρ Values (3·9 and 4·0 at 25 °C, for azoxy formation and oxidation respectively) are consistent with the presence of a negative charge in the transition state, the rate-determining steps being the formation of RC₆H₄NOH· from RC₆H₄NO and MeO^– for azoxy formation and the reduction of RC₆H₄NO₂^– by MeOH for oxidation. Activation parameters are discussed in the light of the proposed mechanism.