Which one of the following reaction is an example of free radical substitution reaction?

Options

A.
B.
C.
D.

Answer

To determine which reaction is an example of a free radical substitution reaction, we need to analyze the options provided. Free radical substitution reactions typically involve the substitution of one atom or group in a molecule by a free radical, often seen in halogenation reactions.

### Step-by-Step Solution:

1. **Identify the Reaction Types**:
- Understand the different types of reactions: elimination, substitution, and isomerization.
- Elimination reactions involve the removal of atoms or groups from a molecule, leading to the formation of a double bond.
- Substitution reactions involve replacing one atom or group in a molecule with another atom or group.
- Isomerization reactions involve rearranging the structure of a molecule without changing its molecular formula.

2. **Analyze the Given Reactions**:
- **Option 1**: C2H5OH + H2SO4 (heat) → CH2=CH2 + H2O
- This is an elimination reaction, where water is removed, and a double bond is formed.
- **Option 2**: CH3CH2Br + F2 → CH3CH2F + BrF
- This is a halogen exchange reaction, where bromine is replaced by fluorine. It does not involve free radicals.
- **Option 3**: CH3Cl + Cl2 → CH3Cl + Cl (free radical substitution)
- This reaction involves chlorine radicals substituting chlorine in the molecule, indicating a free radical substitution reaction.
- **Option 4**: CH4 + Cl2 (light) → CH3Cl + HCl
- This is a classic example of a free radical substitution reaction, where chlorine radicals replace hydrogen atoms in methane.

3. **Choose the Correct Option**:
- Based on the analysis, **Option 4** (CH4 + Cl2 (light) → CH3Cl + HCl) is the correct answer as it exemplifies a free radical substitution reaction.

### Final Answer:
The reaction that is an example of a free radical substitution reaction is **Option 4**: CH4 + Cl2 (light) → CH3Cl + HCl.

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