A statement of Assertion is given followed by a corresponding statement of Reason (R). Choose the correct answer from the given options.

Assertion: Addition reaction of water to but-1-ene in acidic medium yields butan-1-ol.

Reason: Addition of water in acidic medium proceeds through the formation of primary carbocation.

Both Assertion and Reason are incorrect

The correct answer is option 4. Both Assertion and Reason are incorrect.

To understand why both statements fail, we need to look at the mechanism of acid-catalyzed hydration of alkenes, which follows Markovnikov's Rule.

Assertion: "Addition reaction of water to but-1-ene in acidic medium yields butan-1-ol."

• The Reality: When but-1-ene ($CH_{3}-CH_{2}-CH=CH_{2}$) reacts with water in the presence of an acid catalyst ($H^{+}$), the hydroxyl group ($-OH$) attaches to the carbon with the fewer hydrogen atoms.
• The Product: This results in the formation of butan-2-ol, not butan-1-ol.

Reason: "Addition of water in acidic medium proceeds through the formation of primary carbocation."

• The Reality: The reaction proceeds via the formation of the most stable carbocation.
• The Comparison: For but-1-ene, the proton ($H^{+}$) adds to the terminal carbon ($C_{1}$), creating a secondary carbocation at $C_{2}$. A secondary carbocation is much more stable than a primary carbocation due to inductive effects and hyperconjugation.
• Conclusion: The reaction specifically avoids the formation of a primary carbocation whenever a more stable secondary or tertiary intermediate is possible.