Which of the following is a free radical susbtitution reaction ?

Options

A. Benzene + `Me - Cl overset ("Anhyd.") underset (AlCl_3) rarr Ph-CH_3`
B.
C.
D.

Explanation

To determine which of the given reactions is a free radical substitution reaction, we will analyze each option step by step.

### Step 1: Analyze the first reaction
**Reaction:** Benzene + CH3Cl in the presence of AlCl3
**Mechanism:** This reaction involves electrophilic aromatic substitution. The AlCl3 acts as a Lewis acid, facilitating the generation of a methyl cation (CH3+), which then attacks the benzene ring. The chlorine atom is eliminated as a chloride ion (Cl-).
**Conclusion:** This is not a free radical substitution reaction.

### Step 2: Analyze the second reaction
**Reaction:** AgNO2 with a substrate leading to a product with NO2
**Mechanism:** This reaction follows the SN1 mechanism, where Ag+ ion forms a carbocation intermediate, and the NO2- ion attacks the carbocation.
**Conclusion:** This is not a free radical substitution reaction.

### Step 3: Analyze the third reaction
**Reaction:** PhCH3 + Cl2 in the presence of sunlight
**Mechanism:** This reaction involves the generation of free radicals. The chlorine molecule (Cl2) dissociates into two chlorine free radicals (Cl•) in the presence of sunlight. One of the chlorine free radicals abstracts a hydrogen atom from the methyl group of toluene (PhCH3), forming a methyl free radical (PhCH2•) and HCl. The methyl free radical then reacts with another chlorine free radical to form the product (PhCH2Cl).
**Conclusion:** This is a free radical substitution reaction.

### Step 4: Analyze the fourth reaction
**Reaction:** Nucleophilic addition reaction involving MeO and H
**Mechanism:** This reaction involves nucleophilic attack by MeO- on a carbonyl compound, leading to the formation of an alcohol product.
**Conclusion:** This is not a free radical substitution reaction.

### Final Conclusion
The correct answer to the question "Which of the following is a free radical substitution reaction?" is the third reaction involving PhCH3 and Cl2 in the presence of sunlight.

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