Dipole-dipole forces act between molecules possessing permanent dipole.
Van der Waals forces are another name for intermolecular forces. Dipole-dipole forces are the most powerful intermolecular forces that can occur. The attraction between molecules with permanent dipoles is known as dipole-dipole forces and these are the polar molecules.
What are dipole-dipole forces?
The forces between dipoles when they are very close together or touching each other are known as dipole-dipole forces. One polar molecule’s δ- end attracts the δ+ end of another, drawing them together. The forces may be either attractive or repulsive depending on the orientation of the dipoles, but the more stable and likely configuration would increase the attractive interactions.