Non-covalent interactions

A non-covalent interaction differs from a covalent bond in that it does not involve the sharing of electrons, but rather involves more dispersed variations of electromagnetic interactions between molecules or within a molecule. The chemical energy released in the formation of non-covalent interactions is typically on the order of 1-5 kcal/mol (1000–5000 calories per 6.02 x 10^23 molecules). Non-covalent interactions can be classified into different categories, such as electrostatic, π-effects, van der Waals forces, and hydrophobic effects.

Non-covalent interactions are critical in maintaining the three-dimensional structure of large molecules, such as proteins and nucleic acids. In addition, they are also involved in many biological processes in which large molecules bind specifically but transiently to one another (see the properties section of the DNA page). These interactions also heavily influence drug design, crystallinity and design of materials, particularly for self-assembly, and, in general, the synthesis of many organic molecules.

Intermolecular forces are non-covalent interactions that occur between different molecules, rather than between different atoms of the same molecule

For a more detailed introduction to electrostatics, see Coulomb's Law

Ionic interactions involve the attraction of ions or molecules with full permanent charges of opposite signs. For example, sodium fluoride involves the attraction of the positive charge on sodium (Na⁺) with the negative charge on fluoride (F⁻). These bonds are harder to break than covalent bonds because there is a strong electrostatic interaction between oppositely charged ions. However, this particular interaction is easily broken upon addition to water, or other highly polar solvents.

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