Final answer:
A dipole-dipole interaction is classified as a hydrogen bond when the molecule contains bonds between hydrogen and highly electronegative atoms like F, O, or N, leading to strong intermolecular forces and unique properties.
Step-by-step explanation:
In order for a dipole-dipole interaction to be classified as a hydrogen bond, the molecule must contain O-H, N-H, or H-F bonds. These bonds are unique due to the high electronegativity of F, O, and N compared to hydrogen, creating a significant dipole with a dense positive charge on the smaller hydrogen atom.
Hydrogen can penetrate into tighter spaces, allowing strong interactions between hydrogen's delta positive (δ+) and the delta negative (δ−) of an adjacent electronegative atom. Hydrogen bonds are significantly stronger than other types of dipole-dipole interactions, which gives substances like water high boiling points and excellent solvent properties due to the strong intermolecular forces.