Halogenation of alkanes does not occur in …………

Answer

To solve the question "Halogenation of alkanes does not occur in …………", we need to understand the conditions required for the halogenation reaction to take place.

### Step-by-Step Solution:

1. **Understanding Halogenation**: Halogenation is a reaction where alkanes react with halogens (like chlorine or bromine) to form haloalkanes. A common example is the reaction of methane (CH₄) with chlorine (Cl₂).

2. **Reaction Conditions**: The reaction between alkanes and halogens typically requires specific conditions to occur. One critical condition is the presence of light, specifically ultraviolet (UV) light or sunlight.

3. **Free Radical Mechanism**: The halogenation of alkanes proceeds through a free radical mechanism. This involves the formation of free radicals, which are highly reactive species. The initiation of this reaction requires energy, which is provided by sunlight.

4. **Role of Sunlight**: Sunlight acts as a reaction initiator. Without sunlight, the energy required to initiate the formation of free radicals is not available, and thus the halogenation reaction cannot proceed.

5. **Conclusion**: Since the halogenation of alkanes cannot occur without the presence of light, we conclude that halogenation does not occur in the absence of light.

### Final Answer:
Halogenation of alkanes does not occur in **dark**.