Question

Similarity and difference between hydrogen bonds and van der waals bonds

Answer 1

However, some definitions classify hydrogen bonds and van der Waals forces as two different types of intermolecular forces. In one classification, van der Waals forces must involve at least one non-permanent dipole. Hydrogen bonding involves two permanent dipoles, of course.

The definition preferred by IUPAC is different again. It includes permanent dipole-permanent dipole forces (Keesom forces) in van der Waals forces, but does not include hydrogen bonds. The main difference between “ordinary” permanent dipole-permanent dipole forces and hydrogen bonds is that hydrogen bonds are significantly stronger.

I believe that for a long time the terms “van der Waals forces” and “dispersion forces” (involving non-permanent dipoles) were used to mean the same thing. However, in modern usage, “van der Waals forces” is sometimes used loosely to cover all of the intermolecular forces, according to the authoritative IUPAC Gold Book.