Dipole-dipole Interactions

• are stronger intermolecular forces than Dispersion forces
• occur between molecules that have permanent net dipoles (polar molecules), for example, dipole-dipole interactions occur between SCl₂ molecules, PCl₃ molecules and CH₃Cl molecules.
  If the permanent net dipole within the polar molecules results from a covalent bond between a hydrogen atom and either fluorine, oxygen or nitrogen, the resulting intermolecular force is referred to as a hydrogen bond (see below).
• The partial positive charge on one molecule is electrostatically attracted to the partial negative charge on a neighbouring molecule.

from-http://www.ausetute.com.au/intermof.html