Arrange the following alkyl halides in increasing order of boiling points

(A) 1-lodobutane
(B) 1-Bromobutane
(C) 1-Chlorobutane
(D) Butane

Choose the correct answer from the options given below:

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

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

Boiling points of these compounds increase with increasing molecular weight (molar mass) because stronger van der Waals forces require more energy to overcome. All are non-polar or nearly non-polar molecules of similar shape (straight chain), so polarity differences are negligible compared to mass.

Molar masses:

• (D) Butane (C₄H₁₀): 58 g/mol
• (C) 1-Chlorobutane (C₄H₉Cl): 92.5 g/mol
• (B) 1-Bromobutane (C₄H₉Br): 137 g/mol
• (A) 1-Iodobutane (C₄H₉I): 184 g/mol

Thus, increasing order of boiling points: Butane < 1-Chlorobutane < 1-Bromobutane < 1-Iodobutane, i.e., (D) < (C) < (B) < (A).

Actual approximate boiling points confirm this:

• Butane: −0.5 °C
• 1-Chlorobutane: 78 °C
• 1-Bromobutane: 101 °C
• 1-Iodobutane: 130 °C