Final answer:
The correct statement regarding nucleophilic acyl substitution is E: addition of a nucleophile to the carbonyl is followed by loss of the leaving group, which is different from an SN2 reaction that proceeds in a concerted step.
Step-by-step explanation:
The correct statement regarding nucleophilic acyl substitution is E. Addition of a nucleophile to the carbonyl is followed by loss of the leaving group. This sequence of events initiates with a nucleophile attacking the electrophilic carbon of the carbonyl group, forming a tetrahedral intermediate. The leaving group then departs, resulting in the regeneration of the carbonyl group. This mechanism is distinct from the SN2 reaction, in which a nucleophile attacks and a leaving group departs simultaneously in a single, concerted step with inversion of stereochemistry, commonly seen in primary alkyl halides substitutions.
As for nucleophilic acyl substitution reactions, they can proceed under various conditions. If the nucleophile is neutral, it may acquire a positive charge upon donating a pair of electrons and become deprotonated afterward. If the nucleophile is anionic, no positive charge is introduced, and the overall substitution reaction may proceed via an SN1 or SN2 pathway, depending on factors such as the substrate, solvent, and nucleophile.