Arrange the following compounds in the increasing order of their boiling points.
(A) n-Butane
(B) Propanol
(C) Propanal
(D) Acetone
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A), (C), (D), (B)
All four compounds have almost the same molar mass (58–60 g mol−1), so the type of intermolecular force decides the boiling point:
First, (A) n-butane (273 K): non-polar, only weak van der Waals forces.
Second, (C) propanal (322 K): polar C=O group, dipole-dipole attractions.
Third, (D) acetone (329 K): also dipole-dipole attractions, with a slightly larger dipole than propanal.
Fourth, (B) propanol (370 K): intermolecular hydrogen bonds through its –OH group.
Shortcut: n-Butane (A) boils lowest and propanol (B) highest. Only Option (1) starts with (A) and ends with (B).
NCERT (2026-27 edition):
Physical Properties
