Final answer:
An amine group on the aromatic ring increases the electron density, theoretically making it more reactive. However, for alkylations and acylations, this electron-rich environment can repel incoming electrophiles, rendering the ring less reactive.
Step-by-step explanation:
When an amine group is attached to an aromatic ring, it affects the reactivity towards alkylations and acylations. The amine group is an electron-donating group, increasing the electron density of the aromatic ring, which would typically enhance the ring's reactivity. However, in the context of acylations and alkylations, the increased electron density can make the aromatic ring less susceptible to further electrophilic attack because the electron-rich environment repels incoming electrophiles. This should not be confused with the reactivity of amides, which are less reactive due to the resonance stabilization that makes the carbonyl carbon less electrophilic. Reactions involving nucleophilic aromatic substitutions require electron-withdrawing groups on the aromatic ring that make it more accepting of a nucleophile. Amines, being poor leaving groups and good nucleophiles, fit poorly in the role required for electrophilic aromatic substitutions that alkylations and acylations typically involve.