Which of the following alkyl halides has the highest boiling point ?

The correct answer is Option (1) → Bromoform

The boiling point of a haloalkane rises with the strength of its van der Waals forces, which grow with molecular mass and the number of electrons. Two things increase them in halomethanes:

• a heavier halogen (for the same alkyl group: RI > RBr > RCl > RF), and

• more halogen atoms on the carbon.

Comparing the four compounds (molar mass and boiling point):

• Chloromethane, \( \ce{CH3Cl} \): 50.5 g mol⁻¹, 249 K

• Bromomethane, \( \ce{CH3Br} \): 95 g mol⁻¹, 277 K

• Dibromomethane, \( \ce{CH2Br2} \): 174 g mol⁻¹, 370 K

• Bromoform, CHBr₃: 253 g mol⁻¹, 423 K

So bromoform, with three bromine atoms, has the highest boiling point.

Why the other options are incorrect

• Option (2) Bromomethane — Incorrect. Only one bromine atom; it is a gas at room temperature.

• Option (3) Chloromethane — Incorrect. The lightest, with one chlorine atom; it is also a gas at room temperature.

• Option (4) Dibromomethane — Incorrect. Two bromine atoms, one fewer than bromoform, so weaker forces.

NCERT (2026-27 edition):
Physical Properties – …

Note: The same/similar question has been asked in different years by NTA as per the details given below: