Account for the fact that fairly reactive arenes (e.g., benzene, toluene, and ethylbenzene) are nitrated with excess nitric acid in nitromethane solution at a rate that is independent of the concentration of the arene (i.e., zeroth order). Does this mean that nitration of an equimolal mixture of benzene and toluene would necessarily give an equimolal mixture of nitrobenzene and nitrotoluenes? Why or why not?

A zeroth-order reaction is one in which the rate of the reaction is independent of the concentration of the reactants. In this case, the rate of nitration of arenes (benzene, toluene, and ethylbenzene) is given to be independent of their concentration, hence exhibiting zeroth-order kinetics. Mathematically, for a zeroth-order reaction, the rate law equation is expressed as: Rate = k Here, k is the rate constant.

When nitration of an equimolar mixture of benzene and toluene is carried out, it doesn't necessarily imply that an equimolar mixture of nitrobenzene and nitrotoluenes would be obtained. This is because the kinetics of the nitration process, i.e., the reaction rate, doesn't solely depend on the concentration of the arenes involved. The rate constant k may vary for different arenes, which means that nitration may proceed at different rates for benzene, toluene, and ethylbenzene, even if the reaction is zeroth-order with respect to their concentrations.

To support the explanation provided in the previous step, we must consider the reaction mechanism for the nitration of arenes. Nitration typically occurs via an electrophilic aromatic substitution mechanism, in which a nitronium ion (NO2+) acts as the electrophile. The rates at which nitronium ions attack different arenes could be influenced by their electron density, the presence of electron-donating or electron-withdrawing groups, steric factors, and other factors, which may lead to a deviation from the expected equimolar mixture of nitrobenzene and nitrotoluenes. In conclusion, even though the nitration of fairly reactive arenes follows zeroth-order kinetics with respect to their concentrations, that doesn't mean that nitration of an equimolar mixture of benzene and toluene would necessarily yield an equimolar mixture of nitrobenzene and nitrotoluenes. This is because the rate of nitration depends on other factors such as the specific reactivity of each arene and its reaction mechanism, which may lead to differences in the reaction rate constant k and result in deviation from the expected product distribution.