The Mechanism of Chromatographic Retention - Chromatographic Interactions > Polar Interactions > Dipole-Dipole Interactions. > Page 9

Water strongly associates with itself (by so-called 'hydrogen bonding') which reduces its apparent net dipole moment when calculated from bulk external electrical measurements. In a similar manner, methanol associates strongly with itself and gives low dipole moment values also due to intermolecular field compensation. Consequently, bulk properties measurements will not provide true values for the dipole moment of the individual dipoles. Nevertheless, another molecule approaching a strongly polar moleculesuchas water or methanol will experience the uncompensated field of the single dipole and interact accordingly.

If a molecule contains two dipoles, and they are appropriately oriented, the electric field from one dipole can oppose that from the other, reducing the net field as measured externally. This is called intramolecular compensation.


Figure 3. Schematic Representation of Dipole-Dipole Interaction