Question

The relative ease of dehydration of the following alcohols is
(i) Propan-2-ol (ii) Propan-1-ol (iii) 2-Methylpropan-2-ol

• A. (iii) $>$ (ii) $>$ (i)
• B. (ii) $>$ (i) $>$ (iii)
• C. (ii) $>$ (iii) $>$ (i)
• D. (i) $>$ (ii) $>$ (iii)
• E. (iii) $>$ (i) $>$ (ii)

Hint:

Dehydration order: - Depends on carbocation stability - $3^\circ > 2^\circ > 1^\circ$

Answer 1

Answer: (E)

Concept: Dehydration of alcohols occurs via carbocation formation (E1 mechanism for 2° and 3° alcohols). Stability of carbocation determines ease: \[ \text{Tertiary} > \text{Secondary} > \text{Primary} \]

Step 1: Classify alcohols.

• (iii) 2-Methylpropan-2-ol $\rightarrow$ tertiary alcohol
• (i) Propan-2-ol $\rightarrow$ secondary alcohol
• (ii) Propan-1-ol $\rightarrow$ primary alcohol

Step 2: Arrange by carbocation stability.
\[ \text{Tertiary} > \text{Secondary} > \text{Primary} \]

Step 3: Final order.
\[ (iii) > (i) > (ii) \]