試題詳解

15. In the Friedel-Crafts alkylation of benzene, dialkylation is often a significant by-product. In the Friedel-Crafts acylation of benzene, diacylation is not a significant by-product. Which of the following is the primary reason for this difference?
(A) Alkyl groups activate the ring to further substitution, acyl groups deactivate it.
(B) AlkyI groups are less sterically hindered than acyl groups.
(C) Acyl cations are more difficult to make with Lewis acids.
(D) Unlike acyl cations, carbocations can undergo rearrangements.