Question

The dehydration of 1$^\circ$, 2$^\circ$ and 3$^\circ$ alcohols follows the order :

• A. 2$^\circ$ > 1$^\circ$ > 3$^\circ$
• B. 3$^\circ$ > 2$^\circ$ > 1$^\circ$
• C. 1$^\circ$ > 2$^\circ$ > 3$^\circ$
• D. 1$^\circ$ > 3$^\circ$ > 2$^\circ$

Hint:

Whenever dehydration proceeds through carbocation formation, remember: more stable carbocation means faster dehydration.

Answer 1

The Correct Option is B

Step 1: Dehydration mechanism.
Dehydration of alcohols in acid proceeds via carbocation intermediate formation. The stability of the carbocation determines how readily the alcohol dehydrates.
Step 2: Carbocation stability order.
$3^\circ > 2^\circ > 1^\circ$: more alkyl groups stabilize the positive charge through hyperconjugation and the inductive (+I) effect.
Step 3: Dehydration order follows carbocation stability.
The more stable the carbocation, the lower the activation energy, and the faster the dehydration.
\[ \boxed{3^\circ > 2^\circ > 1^\circ} \]