Some alkyl halides undergo substitutionn whereas some undergo elimination reaction on treatment with bases. Discuss the structural features of alkyl halides with the help of examples which are responsible for this difference.

Explanation

To understand why some alkyl halides undergo substitution reactions while others undergo elimination reactions when treated with bases, we need to analyze the structural features of alkyl halides and how these features influence the reaction pathway.

### Step 1: Classification of Alkyl Halides
Alkyl halides can be classified based on the degree of the carbon atom to which the halogen is attached:
- **Primary (1°) Alkyl Halides**: The carbon attached to the halogen is connected to only one other carbon (e.g., RCH₂X).
- **Secondary (2°) Alkyl Halides**: The carbon attached to the halogen is connected to two other carbons (e.g., R₂CHX).
- **Tertiary (3°) Alkyl Halides**: The carbon attached to the halogen is connected to three other carbons (e.g., R₃CX).

...