The two N-containing isomers below have a boiling point difference of 19.0 °C. Meanwhile, the two O-containing isomers have a boiling point difference of 83.2 °C. The two N-containing isomers have a much smaller boiling point difference than the two O-containing isomers. Explain this observation.

• A. Since the two N-containing isomers have a much larger molecular weight difference than the two O-containing isomers, the difference in the strength of Van der Waals forces that must be overcome is larger.
• B. Since the two N-containing isomers have a much smaller molecular weight difference than the two O-containing isomers, the difference in the strength of Van der Waals forces that must be overcome is also smaller.
• C. Since an N-H bond is more polarized than an O-H bond, the presence of hydrogen bonding more effectively increases the strength of intermolecular attraction and the energy required to disrupt interactions when the N-H bond is involved compared to when the O-H bond is involved.
• D. Since an O-H bond is more polarized than an N-H bond, the presence of hydrogen bonding more dramatically increases the strength of intermolecular attraction and the energy required to disrupt interactions when the O-H bond is involved compared to when the N-H bond is involved.

Answer: (D)