Arrange the following compounds in the decreasing order of their boiling points:
(A) Butyraldehyde
(B) n-Butyl alcohol
(C) Sec-butyl alcohol
(D) n-butane
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (B), (C), (A), (D)
To arrange them in decreasing order of boiling points, consider the intermolecular forces:
- Alcohols have hydrogen bonding → highest boiling points
- Among alcohols, less branched (n-butyl alcohol) has a higher boiling point than more branched (sec-butyl alcohol)
- Aldehydes have dipole–dipole interactions (no H-bonding)
- Alkanes have only weak London forces → lowest boiling point
So the order is:
n-Butyl alcohol (B) > sec-Butyl alcohol (C) > Butyraldehyde (A) > n-Butane (D)