Assertion (A): Aromatic carboxylic groups do not undergo Friedel- Crafts reaction.
Reason (R): Carboxyl group is deactivating and the catalyst aluminium chloride gets bonded to the carboxyl group

Options

A. Both A and Rare true and R is the correct explanation of A
B. Both A and R are true but R is NOT the correct explanation of A
C. A is true but R is false
D. A is false and R is true

Explanation

To analyze the assertion and reason provided in the question, we can break down the explanation into a step-by-step solution.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that aromatic carboxylic groups do not undergo Friedel-Crafts reactions.
- Friedel-Crafts reactions are electrophilic aromatic substitution reactions that typically involve the introduction of alkyl or acyl groups onto an aromatic ring.

2. **Understanding the Reason (R)**:
- The reason given is that the carboxyl group (-COOH) is a deactivating group.
- Deactivating groups decrease the electron density of the aromatic ring, making it less reactive towards electrophiles.

3. **Role of the Carboxyl Group**:
- The carboxyl group is indeed a strong electron-withdrawing group due to its -I (inductive) and -M (mesomeric) effects.
- This withdrawal of electron density makes the aromatic ring less nucleophilic and thus less reactive towards electrophilic attack.

4. **Interaction with Aluminium Chloride (AlCl3)**:
- Aluminium chloride (AlCl3) is a Lewis acid and acts as a catalyst in Friedel-Crafts reactions.
- In the presence of a carboxylic acid, AlCl3 can coordinate with the oxygen of the carboxyl group, further decreasing the electron density of the aromatic ring.

5. **Formation of Carbocation**:
- In a typical Friedel-Crafts reaction, a carbocation is generated which then attacks the aromatic ring.
- However, due to the strong deactivating nature of the carboxyl group, the generated carbocation cannot effectively attack the aromatic ring.

6. **Conclusion**:
- Since the carboxyl group is a strong deactivating group and interacts with AlCl3, it prevents the Friedel-Crafts reaction from occurring.
- Therefore, both the assertion and the reason are correct, and the reason correctly explains why the assertion is true.

### Final Answer:
Both the assertion (A) and the reason (R) are correct. The carboxylic group is a strong deactivating group, which prevents the Friedel-Crafts reaction from occurring.

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