Question

Which of the following compounds has lower boiling point?

• A. Fluoromethane
• B. Iodomethane
• C. Bromomethane
• D. Chloromethane

Hint:

For alkyl halides, if the alkyl group is the same, boiling point always increases down the halogen group. If the halogen is the same, boiling point increases with the length of the carbon chain!

Answer 1

The Correct Option is A

Step 1: Same group, one thing changes.
All four are methyl halides, so only the halogen differs. The boiling point depends on the strength of the weak forces between molecules.

Step 2: Link force to size.
A bigger, heavier halogen gives stronger van der Waals forces and a higher boiling point.

Step 3: Find the lowest.
Fluorine is the smallest and lightest, so fluoromethane has the weakest forces and the lowest boiling point.
\[ \boxed{\text{Fluoromethane}} \]