Mechanistic duality of the side-chain substitution in electrophilic aromatic nitration. Unexpected large difference in deuterium isotope effect kH/kD between the side-chain nitration and nitrooxylation of deuterated p-xylenes

A large difference in deuterium kinetic isotope effect observed between the side-chain nitration and nitrooxylation of deuterated p-xylenes, 1,4-(CH3)(CD3)C6H4 and 1,4-(CD3)2C6D4, suggests the operation of different mechanisms for these two types of side-chain substitution.