Dehydration of 1-butanol or 2-butanol with conc. `H_2SO_4` always gives the same mixture of 2-butene (80 %) and 1-butene (20 %) but dehydrohalogenation of 1-bromobutane with alc. KOH gives 1-butene as the major product while that of 2-bromobutane gives 2-butene as the major product . Explain why ?

Explanation

To understand the differences in the dehydration of alcohols and the dehydrohalogenation of alkyl halides, let's break down the processes step by step.

### Step 1: Dehydration of 1-butanol and 2-butanol
1. **1-butanol Reaction**:
- When 1-butanol (C4H10O) is treated with concentrated sulfuric acid (H2SO4), the hydroxyl group (-OH) is protonated to form a better leaving group (H2O).
- This leads to the formation of a carbocation. In the case of 1-butanol, the carbocation formed is a primary carbocation (C1).
- Since primary carbocations are not very stable, a hydride shift can occur, resulting in the formation of a more stable secondary carbocation (C2).
- The elimination of a beta hydrogen (H) occurs, leading to the formation of 2-butene as the major product (80%) and 1-butene as a minor product (20%).
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