Attractive forces between permanent dipoles of polar molecules are called?

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

Answer: (B)

Think about how molecules with a permanent separation of charge interact. Polar molecules carry a partial negative charge on one end and a partial positive charge on the other, so the attraction between the positive end of one molecule and the negative end of another is an intermolecular force that depends on how the dipoles are oriented and how far apart they are. This specific interaction is called dipole-dipole interactions. It’s distinct from London dispersion forces, which come from temporary fluctuations in electron distribution and can occur in nonpolar molecules as well; hydrogen bonding is a special, stronger form of dipole-dipole interaction that occurs when hydrogen is bonded to nitrogen, oxygen, or fluorine; and electrostatic interactions is a broad term for any Coulombic attraction or repulsion not specifically naming permanent dipoles. So the attractive force between permanent dipoles of polar molecules is dipole-dipole interactions.