A : When 2-fluoro butane is reacted with alcoholic KOH then butene-1 is formed as major product.
R: Butene-2 is more stable than butene-1.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1).
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2)
C. if Assertion is true statement but Reason is false, then mark (3)
D. If both Assertion and Reason are false statements, then mark (4)

Answer

To solve the question, we need to analyze the assertion and reason provided:

**Assertion (A):** When 2-fluoro butane is reacted with alcoholic KOH, then butene-1 is formed as the major product.

**Reason (R):** Butene-2 is more stable than butene-1.

### Step-by-Step Solution:

**Step 1: Understand the Reaction**
- 2-fluorobutane (C4H9F) is a halogenated alkane where the fluorine atom is attached to the second carbon.
- When treated with alcoholic KOH, a strong base, it undergoes elimination to form an alkene.

**Step 2: Mechanism of Reaction**
- The reaction proceeds via the E1CB mechanism due to the presence of a poor leaving group (fluorine) and a strong base (alcoholic KOH).
- In the E1CB mechanism, the first step involves deprotonation of a hydrogen atom adjacent to the carbon bearing the leaving group, resulting in the formation of a carbanion.

**Step 3: Identify the Carbanion Formation**
- The carbanion is formed by removing a hydrogen atom from the carbon adjacent to the carbon with the fluorine atom.
- The stability of the carbanion formed will influence which alkene is produced.

**Step 4: Determine the Major Product**
- The carbanion formed from deprotonation will lead to the formation of butene-1 (CH2=CH-CH2-CH3) as the major product.
- This occurs because the carbanion stability is affected by the inductive effect of the adjacent methyl group, making the pathway to butene-1 more favorable.

**Step 5: Analyze the Reason**
- Butene-2 (CH3-CH=CH-CH3) is indeed more stable than butene-1 due to hyperconjugation and the greater number of alkyl groups attached to the double bond.
- However, the reason does not explain why butene-1 is the major product in this reaction.

**Step 6: Conclusion**
- Both the assertion and the reason are true, but the reason does not correctly explain the assertion. Therefore, the correct conclusion is that the assertion is true, and the reason is also true, but it does not provide the correct explanation for the assertion.

### Final Answer:
Both assertion and reason are true, but the reason is not the correct explanation of the assertion.

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