Which of the following will have the lowest boiling point?

• A. CH₃–O–CH₃
• B. KI
• C. C₆H₅OH
• D. C₆H₁₄
• E. C₆₀

Answer: (D)

Verified step by step guidance

1. Identify the types of intermolecular forces present in each compound. CH3–O–CH3 (dimethyl ether) has dipole-dipole interactions and London dispersion forces. KI (potassium iodide) is ionic and has strong ionic bonds. C6H5OH (phenol) has hydrogen bonding, dipole-dipole interactions, and London dispersion forces. C6H14 (hexane) has only London dispersion forces. C60 (buckminsterfullerene) also has London dispersion forces.
2. Recall that the strength of intermolecular forces affects the boiling point. Stronger intermolecular forces result in higher boiling points because more energy is required to separate the molecules.
3. Compare the strength of the intermolecular forces: Ionic bonds (KI) are generally stronger than hydrogen bonds (C6H5OH), which are stronger than dipole-dipole interactions (CH3–O–CH3), which are stronger than London dispersion forces (C6H14 and C60).
4. Consider the molecular size and shape: Larger molecules with more electrons, like C60, have stronger London dispersion forces compared to smaller molecules like C6H14.
5. Determine which compound has the weakest intermolecular forces and thus the lowest boiling point. Since C6H14 has only London dispersion forces and is smaller than C60, it will have the lowest boiling point among the given options.