How do you account for the formation of ethane during chlorination of methane ?

Explanation

To account for the formation of ethane during the chlorination of methane, we can break down the process into several key steps: initiation, propagation, and termination. Here’s a step-by-step explanation:

### Step 1: Initiation
- The chlorination process begins with the initiation step, where chlorine gas (Cl₂) is exposed to energy (usually heat or light, represented as Hν). This energy causes the Cl-Cl bond to break through a process called homolytic cleavage, resulting in the formation of two chlorine free radicals (Cl•).

### Step 2: Propagation
- In the propagation step, one of the chlorine free radicals (Cl•) reacts with methane (CH₄). The chlorine radical abstracts a hydrogen atom from methane, resulting in the formation of a methyl radical (CH₃•) and hydrochloric acid (HCl).

**Reaction:**
Cl• + CH₄ → CH₃• + HCl

- The newly formed methyl radical (CH₃•) can now react with another chlorine molecule. The methyl radical attacks another Cl₂ molecule, leading to the formation of chloromethane (CH₃Cl) and regenerating another chlorine radical.

**Reaction:**
CH₃• + Cl₂ → CH₃Cl + Cl•

### Step 3: Formation of Ethane
- The key to understanding the formation of ethane (C₂H₆) lies in the termination step. If two methyl radicals (CH₃•) collide, they can combine to form ethane.

**Reaction:**
CH₃• + CH₃• → C₂H₆

### Step 4: Termination
- In the termination step, free radicals combine to form stable products. Various combinations can occur, including:
- Two methyl radicals forming ethane (C₂H₆).
- A chlorine radical combining with a methyl radical to form chloromethane (CH₃Cl).
- Two chlorine radicals recombining to form chlorine gas (Cl₂).

### Conclusion
- Thus, during the chlorination of methane, ethane is formed as a byproduct due to the combination of two methyl radicals. This process illustrates the radical mechanism of chlorination, where free radicals play a crucial role in the formation of various products.

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