noncovalent

Noncovalent refers to interactions between atoms or molecules that do not involve the sharing of electron pairs to form covalent bonds. These interactions include hydrogen bonds, electrostatic or ionic interactions between charged or polar groups, dipole–dipole and dipole–induced dipole forces, and London dispersion (van der Waals) forces. Hydrophobic effects, although not a single type of bond, also arise from noncovalent forces in aqueous environments. Collectively, noncovalent interactions govern the arrangement and behavior of matter at molecular and supramolecular scales.

The strength of noncovalent interactions is generally weaker than covalent bonds on a per-interaction basis, typically ranging from a fraction to a few tens of kilojoules per mole, depending on the type and environment. Hydrogen bonds are commonly several kilojoules per mole, while dispersion forces can accumulate to significant stabilizing energies in large molecules. The forces are often directional (as with hydrogen bonds and certain ionic interactions) or highly sensitive to distance and surrounding medium.

Noncovalent interactions play central roles in biology, chemistry, and materials science. They drive protein folding and stabilizing tertiary and quaternary structures, govern DNA base pairing, and mediate enzyme–substrate and receptor–ligand recognition. In chemistry and materials science, they underlie crystal packing, self-assembly, supramolecular chemistry, and the design of sensors and nanomaterials. Solvent, temperature, and concentration can modulate these interactions, sometimes enhancing or suppressing specific contacts.

Because noncovalent forces enable selective binding and reversible associations, they are foundational to fields such as drug design, catalysis, and molecular engineering.