What type of interactions are permanent dipole-dipole interactions?

Permanent dipole-dipole interactions occur between neighboring polar molecules, which possess permanent dipoles due to differences in electronegativity between atoms within a molecule. These differences create regions of partial positive and partial negative charges, resulting in a polar bond. The attraction occurs because the positive end of one polar molecule is attracted to the negative end of another, leading to a significant interaction compared to nonpolar molecules.

The strength of dipole-dipole interactions is typically stronger than the interactions between nonpolar molecules, which rely solely on London dispersion forces. Furthermore, while these interactions are relevant for substances composed of polar molecules, they do not specifically require that the molecules be of the same type—they can occur between dissimilar polar molecules as well. Thus, the characterization of these interactions as weak electrostatic attractions effectively captures their nature in comparison to other types of intermolecular forces.