Which of the following has the highest boiling point?

Correct option is D

The correct answer is (d) Alkynes.
• Alkynes generally have higher boiling points compared to alkenes and alkanes due to the triple bond between carbon atoms, which increases the molecular weight and intermolecular forces.
Facts to Remember:
• Boiling points of organic compounds increase with molecular weight and stronger intermolecular forces.
• Free carbon dioxide is a gas at standard temperature and pressure, thus it has a very low boiling point compared to hydrocarbons.
• Alkynes, with their triple bonds, have stronger van der Waals forces than alkenes and alkanes of similar molecular weight, leading to higher boiling points.