Choose the correct sequence for the increasing boiling point of the following compounds.

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

Choose the correct answer from the options given below:

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

The correct answer is Option (1) → (C), (D), (B), (A)
Ethanol < Propan-1-ol < Butan-2-ol < Pentan-1-ol
Boiling point of alcohols depends mainly on:

1. Molecular mass / chain length – Higher mass → higher boiling point.

2. Branching – More branching → lower boiling point (less surface area, weaker intermolecular forces).

3. Hydrogen bonding – Present in all, so differences come mostly from size and structure.

• Ethanol (C₂) – smallest → lowest boiling point.

• Propan-1-ol (C₃) – longer chain → higher than ethanol.

• Butan-2-ol (C₄, branched at 2-position) – higher mass than propanol, so higher boiling point despite slight branching.

• Pentan-1-ol (C₅, straight chain) – largest molecule → strongest intermolecular forces → highest boiling point.

Hence, (C) < (D) < (B) < (A).