Assertion : Carboxylic acids do not undergo Friedel - Crafts reaction.
Reason : Carboxyl group is meta-directing group.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Explanation

To analyze the assertion and reason provided in the question, we will break down the concepts step by step.

### Step 1: Understanding the Assertion
The assertion states that "Carboxylic acids do not undergo Friedel-Crafts reaction."

**Explanation:**
Friedel-Crafts reactions involve the alkylation or acylation of aromatic compounds using alkyl halides or acyl halides in the presence of a Lewis acid catalyst (like AlCl3). Carboxylic acids, such as benzoic acid, do not participate in these reactions because the carboxyl (-COOH) group is an electron-withdrawing group. This decreases the electron density of the aromatic ring, making it less reactive towards electrophilic substitution reactions.

**Hint for Step 1:** Recall the nature of Friedel-Crafts reactions and the role of electron-withdrawing groups in aromatic reactivity.

### Step 2: Understanding the Reason
The reason states that "The carboxyl group is a meta-directing group."

**Explanation:**
The carboxyl group (-COOH) is indeed a meta-directing group in electrophilic aromatic substitution reactions. This means that if an electrophile were to attack the aromatic ring, it would preferentially do so at the meta position relative to the carboxyl group rather than the ortho or para positions. This is because the carboxyl group decreases the electron density at the ortho and para positions, making them less favorable for electrophilic attack.

**Hint for Step 2:** Remember the directing effects of substituents on aromatic rings and how they influence the position of electrophilic attack.

### Step 3: Evaluating the Assertion and Reason
Both the assertion and the reason are true statements:
- Carboxylic acids do not undergo Friedel-Crafts reactions due to the electron-withdrawing nature of the carboxyl group.
- The carboxyl group is a meta-directing group in electrophilic aromatic substitution reactions.

However, the reason does not correctly explain why carboxylic acids do not undergo Friedel-Crafts reactions. The reason focuses on directing effects rather than the reactivity of the carboxylic acid itself.

**Conclusion:**
- Assertion: True
- Reason: True, but does not explain the assertion.

### Final Answer:
The correct answer is that both statements are true, but the reason does not correctly explain the assertion. Therefore, the answer is **B**.