Tuesday, September 3, 2013

Non-covalent interactions (part 1)

Today I will dedicate a post to a type of weak interactions that is often overlooked in chemistry classes (probably because they are weaker than covalent bonds ...), but in biochemistry are equally or more important than the covalent bonds. I'm talking about the non-covalent interactions (or bonds). Before starting to talk about them, it should be highlighted the difference between non-covalent and covalent bonds. In the first there is no sharing of electrons between the atoms participating in the bond, while in the second type there is sharing of the electrons (bonding electrons). Because there is no sharing of electrons, the resulting bond is significantly weaker.
There are different types of non-covalent interactions that collectively are known as van der Waals forces. The main types are:
- Ion interactions
- Dipole-dipole interactions
- Ion-dipole interactions
- Hydrogen bonds
- London dispersion forces

Often these interactions are referred to intermolecular forces, that means, forces that exist between molecules. In fact, it is the existence of interactions of this type that allows the molecules to interact with each other, thus justifying the existence of substances in liquid or solid state. Despite all the intermolecular forces are of this kind, they are also often responsible for interactions that occur between different regions within one molecule, being designated intramolecular forces. This is particularly frequent in the case of biochemistry, where one often deals with macromolecules (large molecules). Therefore, the non-covalent bonds can be intra-or intermolecular.


  1. This page may be useful