Arrange the following alcohols in increasing order of their boiling points.

(A) Propan-1-ol
(B) Butan-2-ol
(C) Butan-1-ol
(D) Pentan-1-ol

Choose the correct answer from the options given below:

(A), (B), (C), (D)

The correct answer is Option (1) → (A), (B), (C), (D)

Boiling point of alcohols depends mainly on:

1. Hydrogen bonding (–OH group) → more H-bonding, higher BP
2. Molecular mass / chain length → longer chain, higher BP
3. Branching → more branching, lower BP

Step 1: Analyze the compounds

• Propan-1-ol (A) →Contains 3 carbon atoms, so it has the lowest molecular mass and lowest boiling point.
• Butan-2-ol (B) → Contains 4 carbons but is a secondary alcohol, meaning it is more branched and therefore has a slightly lower boiling point than the straight-chain isomer.
• Butan-1-ol (C) → Contains 4 carbons and is a straight-chain alcohol, giving stronger intermolecular forces and higher boiling point than butan-2-ol.
• Pentan-1-ol (D) → Contains 5 carbons, giving the strongest van der Waals forces and the highest boiling point.

Step 2: Arrange in increasing order of BP

$\text{Propan-1-ol (A)} < \text{Butan-2-ol (B)} < \text{Butan-1-ol (C)} < \text{Pentan-1-ol (D)}$