Aryl halides are less reactive towards nucleophilic substitution reaction as compared to alkyl halides due to

Options

A. formation of a less stable carbonium ion in aryl halides
B. resonance stabilisation in ary halides
C. presence of double bonds in alkyl halides
D. inductive effect in aryl halides.

Answer

To understand why aryl halides are less reactive towards nucleophilic substitution reactions compared to alkyl halides, we can analyze the factors involved in these reactions step by step.

### Step-by-Step Solution:

1. **Understanding Nucleophilic Substitution**:
- In nucleophilic substitution reactions, a nucleophile attacks the carbon atom bonded to the leaving group (halogen) and replaces it. The stability of the intermediate formed during this process is crucial for the reaction to proceed.

2. **Structure of Alkyl Halides**:
- Alkyl halides have a carbon atom bonded to a halogen (like Cl, Br, or I). When a nucleophile approaches, it can easily attack the carbon atom because there is no significant resonance stabilization of the carbon-halogen bond. This allows the bond to break and the nucleophile to substitute the halogen.

3. **Structure of Aryl Halides**:
- Aryl halides, on the other hand, have a halogen atom bonded to a carbon atom that is part of an aromatic ring (like benzene). The halogen atom has lone pairs of electrons that can participate in resonance with the aromatic system.

4. **Resonance Stabilization**:
- In aryl halides, the lone pair of electrons on the halogen can delocalize into the aromatic ring, creating resonance structures. This delocalization gives the carbon-halogen bond a partial double bond character, making it stronger and less reactive. The resonance structures stabilize the aryl halide and hinder the nucleophile's ability to attack.

5. **Comparison of Stability**:
- The resonance in aryl halides leads to a situation where the carbon-halogen bond is more stable due to the partial double bond character. In contrast, alkyl halides do not have this resonance stabilization, making their carbon-halogen bonds more susceptible to nucleophilic attack.

6. **Conclusion**:
- Therefore, the correct reason why aryl halides are less reactive towards nucleophilic substitution compared to alkyl halides is due to the resonance stabilization in aryl halides, which makes the carbon-halogen bond stronger and less likely to break.

### Final Answer:
Aryl halides are less reactive towards nucleophilic substitution reactions compared to alkyl halides due to **resonance stabilization in the aryl halides**.