Benzoic acid on reaction with ammonia gives product [A], [A] on dehydration gives [B]. In this reaction [A] and [B] are respectively:

Question

Accepted Answer

To understand why Option 2 is the correct answer, let's break down the reaction process and analyze each step:

1. **Reaction of Benzoic Acid with Ammonia:**
   - When benzoic acid reacts with ammonia, it forms ammonium benzoate. This is a straightforward acid-base reaction where the acidic proton of benzoic acid is replaced by an ammonium ion, resulting in the formation of ammonium benzoate. Therefore, the product [A] is ammonium benzoate.

2. **Dehydration of Ammonium Benzoate:**
   - Upon heating, ammonium benzoate undergoes dehydration. This process involves the removal of a water molecule, leading to the formation of benzamide. The dehydration of ammonium salts of carboxylic acids typically results in the formation of amides. Therefore, the product [B] is benzamide.

Now, let's examine why the other options are incorrect:

1. **Option 1: Ammonium benzoate and aniline**
   - While ammonium benzoate is correctly identified as product [A], the dehydration of ammonium benzoate does not yield aniline. Aniline is an aromatic amine, and its formation from benzoic acid and ammonia is not feasible through simple dehydration. Therefore, this option is incorrect.

3. **Option 3: Benzamide and aniline**
   - This option incorrectly identifies benzamide as product [A]. Benzamide is actually the product [B] formed after dehydration. Additionally, aniline is not formed in this reaction sequence, making this option incorrect.

4. **Option 4: Benzamide and benzoic acid**
   - This option incorrectly suggests that benzamide is product [A]. Benzamide is the product [B] formed after dehydration. Moreover, benzoic acid is the starting material, not a product of the reaction sequence. Therefore, this option is incorrect.

In conclusion, Option 2 is the correct answer because it accurately describes the formation of ammonium benzoate as product [A] and benzamide as product [B] through the reaction of benzoic acid with ammonia followed by dehydration.