Which interaction involves attractions between permanent dipoles of polar molecules?

• A. London dispersion forces
• B. Hydrogen bonding
• C. Dipole-dipole interactions
• D. Electrostatic interactions

Answer: (C)

When polar molecules have a permanent separation of charge, each molecule has a partial positive end and a partial negative end. The attraction between the positive end of one molecule and the negative end of another is a dipole-dipole interaction. This is the main way permanent dipoles attract each other, and it helps explain why polar substances often have higher boiling points and orient themselves along electric fields or during interactions with other polar species. Hydrogen bonding is a strong, special case of this kind of interaction when hydrogen is bound to highly electronegative atoms like nitrogen, oxygen, or fluorine, but it’s still a dipole-dipole attraction at its core. London dispersion forces arise from temporary fluctuations and occur in all molecules, especially nonpolar ones, and are typically weaker for small polar molecules. Electrostatic interactions is a broader term that includes many charge-based attractions and isn’t specific to permanent dipoles of polar molecules.