Assertion: Electron withdrawing groups in aryl halides decrease the reactivity towards nucleophilic substitution.
Reason: 2,4-Dinitrochlorobenzene is less reactive than chlorobenzene.

Options

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

Explanation

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

### Step 1: Understanding the Assertion
The assertion states that "Electron withdrawing groups in aryl halides decrease the reactivity towards nucleophilic substitution."

- **Explanation**: In nucleophilic substitution reactions, the presence of electron-withdrawing groups (EWGs) such as nitro groups (-NO2) can stabilize the negative charge that develops during the reaction. However, they also make the carbon atom attached to the halogen (like chlorine) less electrophilic because they pull electron density away from the aromatic ring. This can lead to a decrease in reactivity towards nucleophilic substitution.

### Step 2: Understanding the Reason
The reason states that "2,4-Dinitrochlorobenzene is less reactive than chlorobenzene."

- **Explanation**: 2,4-Dinitrochlorobenzene has two nitro groups that are strong electron-withdrawing groups. These groups significantly reduce the electron density on the aromatic ring, making the carbon atom bonded to chlorine less reactive towards nucleophiles compared to chlorobenzene, which has only one chlorine atom and no electron-withdrawing groups.

### Step 3: Evaluating the Assertion and Reason
Now, we need to evaluate whether both the assertion and the reason are true or false.

- **Assertion Evaluation**: The assertion is **true** because electron-withdrawing groups do indeed decrease the reactivity of aryl halides towards nucleophilic substitution.

- **Reason Evaluation**: The reason is **true** as well because 2,4-Dinitrochlorobenzene is indeed less reactive than chlorobenzene due to the presence of the two electron-withdrawing nitro groups.

### Step 4: Conclusion
Both the assertion and the reason are true, and the reason correctly explains the assertion.

### Final Answer
Both the assertion and the reason are true, and the reason correctly explains the assertion.

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