Among the following, which alkyl halide has the highest boiling point?

The correct answer is Option (1) → RI

Alkyl halides are polar molecules held together by dipole-dipole forces and van der Waals forces. For the same alkyl group, a larger halogen atom has more electrons and is more easily polarised, so the van der Waals forces, and with them the boiling point, are greatest for the alkyl iodide, RI.

NCERT (2026-27 edition):
Physical Properties – “… Methyl chloride, methyl bromide, ethyl chloride and some chlorofluoromethanes are gases at room temperature. Higher members are liquids or solids. As we have already learnt, molecules of organic halogen compounds are generally polar. Due to greater polarity as well as higher molecular mass as compared to the parent hydrocarbon, the intermolecular forces of attraction (dipole-dipole and van der Waals) are stronger in the halogen derivatives. … For the same alkyl group, the boiling points of alkyl halides decrease in the order: RI> RBr> RCl> RF. This is because with the increase in size and mass of halogen atom, the magnitude of van der Waal forces increases.”