Hydrogen Bonding

Step 1: Understanding the Concept:
For similar molecules (alkyl halides), the boiling point increases with an increase in molecular weight and the size of the halogen atom due to stronger London dispersion forces.

Step 2: Detailed Explanation:
Among the given halomethanes, CH₃I has the largest and most polarizable iodine atom. This leads to the strongest London dispersion forces between its molecules. CH₃F, CH₃Cl, and CH₃Br are smaller and have weaker intermolecular forces. CH₃CH₂F (ethyl fluoride) has a higher molecular weight than CH₃F but lower than CH₃I. Iodine is much larger and heavier than fluorine, chlorine, or bromine, so CH₃I will have the highest boiling point.

Step 3: Final Answer:
CH₃I has the highest boiling point.