A reinterpretation of the zeroth-order kinetics for nitration in acetic anhydride

Abstract

The nitration of benzene, toluene, m-xylene, and mesitylene in acetic anhydride has been studied using high concentrations of the aromatic compound. Previous observations that the order with respect to the aromatic compound decreases from 1 to 0 as the concentration of the aromatic compound is increased are confirmed. However this change in order is shown to arise mainly from a medium effect, not from the rate-determining formation of the electrophile. Similar medium effects are reported for the addition of inert aromatic compounds to the reaction mixture. This reinterpretation of the zeroth-order kinetic form imposes severe restrictions on the mechanism of formation of the electrophile.