Assertion (A): In nucleophilic substitution reactions the presence of nitro group increases the reaction of aryl halides.
Reason (R): The intermediate carbanion is stabilized due to the presence of nitro group.

Options

A. Both A and R are 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 but R is true.

Explanation

To solve the given assertion and reason question, we will analyze both the assertion and the reason step by step.

### Step 1: Understanding the Assertion
The assertion states that "In nucleophilic substitution reactions, the presence of a nitro group increases the reaction of aryl halides."

- Aryl halides are compounds where a halogen atom (like Cl, Br, I) is bonded to an aromatic ring.
- The presence of a nitro group (–NO2) on the aromatic ring is known to enhance the reactivity of the aryl halide in nucleophilic substitution reactions.

### Step 2: Analyzing the Reason
The reason provided states that "The intermediate carbanion is stabilized due to the presence of the nitro group."

- A carbanion is a negatively charged carbon species that can form during the nucleophilic substitution process.
- The nitro group is an electron-withdrawing group. It pulls electron density away from the aromatic ring, which can stabilize the carbanion formed during the reaction.

### Step 3: Mechanism of Nucleophilic Substitution
1. **Nucleophile Attack**: In a nucleophilic substitution reaction, the nucleophile attacks the carbon atom bonded to the halogen. The carbon atom has a partial positive charge due to the electronegativity of the halogen.

2. **Formation of Carbanion**: When the nucleophile attacks, the bond between the carbon and the halogen breaks, leading to the formation of a carbanion intermediate.

3. **Stabilization of Carbanion**: The nitro group, being electron-withdrawing, helps stabilize the carbanion through resonance. The negative charge on the carbanion can be delocalized onto the nitro group, which stabilizes the intermediate.

### Step 4: Conclusion
Both the assertion and reason are true. The presence of the nitro group increases the reactivity of aryl halides in nucleophilic substitution reactions by stabilizing the intermediate carbanion formed during the reaction.

### Final Answer
- **Assertion (A)**: True
- **Reason (R)**: True
- **Explanation**: The nitro group increases the reactivity of aryl halides in nucleophilic substitution reactions by stabilizing the intermediate carbanion.

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