Photochemical chlorination of alkane is initiated by a process

Options

A. Pyrolysis
B. Substitution
C. Homolysis
D. Peroxidation

Answer

To solve the question regarding the initiation of the photochemical chlorination of alkanes, we can break down the process into clear steps:

### Step-by-Step Solution:

1. **Understanding Photochemical Chlorination**:
- Photochemical chlorination involves the reaction of alkanes with chlorine gas (Cl₂) under the influence of light (denoted as Hν). This process leads to the formation of alkyl chlorides (RCl) and hydrogen chloride (HCl).

2. **Initiation Step**:
- The first step in this reaction is known as the **chain initiation step**. This is where the chlorine molecules (Cl₂) are broken down into chlorine radicals (Cl•).
- This process occurs via **homolytic cleavage**, where the bond between the two chlorine atoms is broken, resulting in the formation of two chlorine radicals.

3. **Homolytic Cleavage**:
- Homolytic cleavage is a type of bond dissociation where each atom involved in the bond takes one of the shared electrons, leading to the formation of two free radicals.
- In the case of Cl₂, the reaction can be represented as:
\[ \text{Cl}_2 \xrightarrow{H\nu} 2 \text{Cl}• \]

4. **Chain Propagation**:
- After the initiation step, the chlorine radicals can react with the alkane (Rh) to form a new radical and HCl. This is known as the **chain propagation step**.
- The reaction can be represented as:
\[ \text{R} + \text{Cl}• \rightarrow \text{R}• + \text{HCl} \]

5. **Chain Termination**:
- Finally, the reaction can terminate when two radicals combine to form a stable product. This is known as the **chain termination step**.
- For example:
\[ \text{R}• + \text{Cl}• \rightarrow \text{RCl} \]

6. **Conclusion**:
- Therefore, the initiation of the photochemical chlorination of alkanes is specifically initiated by the process of **homolysis**.

### Final Answer:
The photochemical chlorination of alkanes is initiated by a process called **homolysis**.

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