The reaction, `CH_4+Cl_2 overset("hv") to , CH_3 Cl+HCl,` occurs through

Options

A. electrophilic substitution
B. nucleophilic substitution
C. free radical substitution
D. none of the above.

Explanation

To determine the type of reaction mechanism for the halogenation of methane, we can break down the process step by step.

### Step-by-Step Solution:

1. **Identify the Reactants and Products**:
- The reactants are methane (CH₄) and chlorine (Cl₂).
- The products are chloromethane (CH₃Cl) and hydrochloric acid (HCl).

2. **Understand the Conditions**:
- The reaction occurs in the presence of sunlight (hv), which provides energy for the reaction to proceed.

3. **Recognize the Type of Reaction**:
- This reaction is a halogenation reaction, specifically chlorination, where hydrogen atoms in methane are substituted by chlorine atoms.

4. **Mechanism of the Reaction**:
- The reaction proceeds through a free radical mechanism. This involves several steps:
- **Initiation**: The chlorine molecules (Cl₂) undergo homolytic cleavage due to the energy from sunlight, producing two chlorine radicals (Cl•).
- **Propagation**:
- The chlorine radical reacts with methane (CH₄) to form a methyl radical (CH₃•) and hydrochloric acid (HCl).
- The methyl radical (CH₃•) can then react with another chlorine molecule (Cl₂) to produce chloromethane (CH₃Cl) and regenerate another chlorine radical (Cl•).
- **Termination**: The reaction continues until all hydrogen atoms in methane are substituted by chlorine, forming products like chloromethane (CH₃Cl) and potentially carbon tetrachloride (CCl₄) if the reaction continues.

5. **Conclusion**:
- The overall mechanism of the reaction is classified as a **free radical substitution reaction**.

### Final Answer:
The reaction `CH₄ + Cl₂ → CH₃Cl + HCl` occurs through a **free radical substitution mechanism**.

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