Consider the nucleophilic addition of ammonia to benzoyl chloride shown below. Which of the following statements is true?

Question

BlackTom AI · Accepted Answer

Acyl chlorides undergo nucleophilic acyl substitution: the carbonyl carbon is strongly electrophilic and is attacked by nucleophiles such as ammonia.

1) Relevant knowledge points and concepts
- Carbonyl reactivity: in an acyl chloride (benzoyl chloride) the C=O carbon is more electrophilic because the chlorine withdraws electron density.
- Nucleophile vs electrophile: ammonia (NH3) is a nucleophile (lone pair on N); the acyl carbon is the electrophile.
- Leaving-group ability: chloride (Cl−) is a good leaving group because its conjugate acid (HCl) is a very strong acid, so Cl− is a relatively stable, weakly basic anion in solution and is well solvated.

2) Step-by-step reaction reasoning (mechanism)
- Step 1: The lone pair on ammonia attacks the electrophilic carbonyl carbon of benzoyl chloride, forming a tetrahedral (addition) intermediate where the oxygen bears a negative charge and nitrogen is temporarily bonded to carbon.
- Step 2: Proton transfer(s) occur within the intermediate (or to another NH3 molecule), generating an -NH2 substituent and a protonated oxygen or ammonium species as needed.
- Step 3: The tetrahedral intermediate collapses: the C–Cl bond breaks and chloride departs, restoring the carbonyl and giving the amide (benzamide) plus Cl−. Often the expelled Cl− protonates an ammonium to give HCl or NH4+Cl−.

3) Intermediate steps shown conceptually
- R–C(=O)–Cl + :NH3 → R–C(OH)(NH3)–Cl (tetrahedral) → collapse → R–C(=O)–NH2 + Cl− (and HCl/NH4+Cl− depending on proton transfers).

4) Why the correct answer is correct
- Option b correctly states that chloride anions are good leaving groups because they are stable in solution: Cl− is the conjugate base of a strong acid (HCl) and is well solvated, making departure favorable in this substitution.

5) Why the other options are incorrect
- a: Incorrect — reaction does occur; acyl chlorides react readily with amines to form amides.
- c: Incorrect — contradicts established leaving-group trends; Cl− is relatively stable, not a poor leaving group.
- d: Incorrect — benzoyl chloride is the electrophile (its carbonyl carbon is attacked), not the nucleophile.
- e: Incorrect — ammonia is a nucleophile (donates its lone pair), not an electrophile.

Conclusion: The correct statement is b, matching the provided answer.

Consider the nucleophilic addition of ammonia to benzoyl chloride shown below. Which of the following statements is true?单项选择题

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