What is the difference between Keesom interactions and London dispersion forces?

Keesom interactions and London dispersion forces are both types of intermolecular forces that play a significant role in determining the physical properties and behaviors of molecules. However, they arise from different mechanisms and have distinct characteristics.

Keesom Interactions:
Keesom interactions, also known as dipole-dipole interactions, occur between molecules that have permanent dipoles. A permanent dipole arises when there is an unequal distribution of electron density within a molecule, resulting in a partial positive charge (δ+) on one end and a partial negative charge (δ-) on the other end. These partial charges create attractive forces between molecules that have complementary orientations of their dipoles.
Key points about Keesom interactions:

They are stronger when the magnitude of the permanent dipole moment is larger.
They are directional in nature, meaning that the strength of the interaction depends on the relative alignment of the dipoles.
Keesom interactions are relatively stronger in polar molecules and can contribute significantly to the overall intermolecular forces in such systems.
Examples of molecules with Keesom interactions include hydrogen fluoride (HF) and water (H2O).
London Dispersion Forces:
London dispersion forces, also known as van der Waals forces or induced dipole-induced dipole interactions, arise due to temporary fluctuations in electron distribution within molecules. At any given moment, an atom or molecule may have a temporary imbalance in electron density, resulting in a temporary partial positive charge (δ+) and a temporary partial negative charge (δ-) within the molecule. These temporary charges induce corresponding fluctuations in the neighboring molecules' electron distribution, leading to attractive forces.
Key points about London dispersion forces:

They are present in all molecules, regardless of whether they have permanent dipoles or not.
These forces are generally weaker than Keesom interactions, but they become significant as the size of the molecules increases.
London dispersion forces increase with increasing molecular size and surface area, as larger molecules tend to have more electrons available for temporary fluctuations.
Molecules with larger numbers of electrons, such as long hydrocarbon chains or noble gases like xenon, exhibit stronger London dispersion forces.
These forces are considered non-directional, as they arise from temporary fluctuations in electron distribution.
In summary, Keesom interactions are specific intermolecular forces that arise between molecules with permanent dipoles, whereas London dispersion forces are more general forces that result from temporary fluctuations in electron density within molecules, regardless of their permanent dipole moments. Both types of forces contribute to the overall intermolecular interactions in different ways, and they collectively determine the physical properties of substances such as boiling points, melting points, and solubility.