A : On dehydration with concentrated `H_(2)SO_(4)` neopentyl alcohul gives 2-methyl butene-2.
R : `3^(@)` carbocation is more stable than `2^(@)` carbocation.

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 both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that neopentyl alcohol, upon dehydration with concentrated sulfuric acid (H₂SO₄), yields 2-methylbutene-2.
- Neopentyl alcohol has the structure:
\[ \text{(CH₃)₄C(OH)CH₂} \]
- When dehydrated, it loses a water molecule (H₂O), leading to the formation of a double bond.

2. **Dehydration Mechanism**:
- The dehydration process involves the formation of a carbocation. Initially, the hydroxyl group (OH) leaves, forming a carbocation.
- The carbocation formed from neopentyl alcohol is initially a primary carbocation, which is less stable.

3. **Carbocation Rearrangement**:
- To stabilize the carbocation, a methyl shift occurs. This rearrangement transforms the primary carbocation into a more stable tertiary carbocation.
- The structure of the tertiary carbocation can be represented as:
\[ \text{(CH₃)₃C⁺} \]
- This tertiary carbocation is more stable due to the inductive effect of the surrounding alkyl groups.

4. **Formation of the Alkene**:
- From the tertiary carbocation, the elimination of a proton (H⁺) occurs, leading to the formation of the double bond.
- The resulting product is 2-methylbutene-2:
\[ \text{CH₃C(CH₃)=CH(CH₂CH₃)} \]

5. **Understanding the Reason**:
- The reason states that a tertiary carbocation is more stable than a secondary carbocation. This is true and is a well-known principle in organic chemistry.
- The stability of carbocations increases with the number of alkyl groups attached to the positively charged carbon atom due to hyperconjugation and the inductive effect.

6. **Conclusion**:
- Both the assertion and the reason are true.
- However, the reason provided does not directly explain the assertion since it compares tertiary and secondary carbocations instead of primary and tertiary. Therefore, while both statements are true, the reason is not the correct explanation for the assertion.

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