Which of the following reactions involve free radical as intermediate ?

Options

A.
B.
C.
D.

Answer

To determine which of the reactions involve free radicals as intermediates, we can analyze each reaction step by step.

### Step 1: Analyze Reaction A (Benzene with Cl2 and FeCl3)
- In this reaction, benzene reacts with chlorine (Cl2) in the presence of iron(III) chloride (FeCl3).
- The FeCl3 acts as a Lewis acid and facilitates the formation of the electrophile Cl+.
- The mechanism involves the formation of a carbocation intermediate, not a free radical.
- **Conclusion**: This reaction does not involve free radicals.

### Step 2: Analyze Reaction B (Alkane with Br2 in sunlight)
- In this reaction, bromine (Br2) reacts with an alkane in the presence of sunlight.
- The sunlight provides energy for the homolytic cleavage of the Br-Br bond, generating two bromine radicals (Br•).
- The bromine radical then abstracts a hydrogen atom from the alkane, forming an alkyl radical (R•).
- The alkyl radical can then react with another bromine radical to form the bromoalkane (RBr).
- **Conclusion**: This reaction involves free radicals as intermediates.

### Step 3: Analyze Reaction C (Alkene with N-bromosuccinimide, NBS)
- In this reaction, N-bromosuccinimide (NBS) reacts with an alkene.
- The N-Br bond in NBS can undergo homolytic cleavage to generate a bromine radical (Br•) and a nitrogen radical (N•).
- The bromine radical abstracts a hydrogen atom from the alkene, forming an allylic radical.
- This allylic radical can then react with another bromine radical to form the brominated product.
- **Conclusion**: This reaction involves free radicals as intermediates.

### Step 4: Analyze Reaction D (Silver Acetate with Br2 in CCl4)
- In this reaction, silver acetate reacts with bromine (Br2) in carbon tetrachloride (CCl4).
- The Br-Br bond undergoes homolytic cleavage to form bromine radicals (Br•).
- The silver acetate can interact with the bromine radical, leading to the formation of a radical on the acetate.
- This radical can then rearrange or react further, involving free radical mechanisms.
- **Conclusion**: This reaction involves free radicals as intermediates.

### Final Conclusion
Based on the analysis:
- **Reactions that involve free radicals as intermediates**: B, C, and D.
- **Reactions that do not involve free radicals**: A.

### Answer: B, C, D involve free radicals as intermediates.

---