Dissociation in chemistry and biochemistry is a general process in which complexes, molecules, or salts separate or split into smaller molecules, ions, or radicals, usually in a reversible manner. Dissociation is the opposite of association and recombination.
Dissociation constant
For reversible dissociations in a chemical_equilibrium
- AB <=> A + B
the dissociation constant Kd is the ratio of dissociated to undissociated compound
- Kd = ([A] · [B]) / [AB]
Salts
The dissociation of salts by solvation in a solvent like water (molecule) means the separation of the anions and cations. The salt can be recovered by evaporation of the solvent. See also: Solubility equilibrium
Acids
The dissociation of acids in a solution means the split-off of a proton H+, see Acid-base reaction theories. This is an equilibrium process, meaning that dissociation and recombination takes place at the same time. The acid dissociation constant Ka is an indicator of the acid strength: stronger acids have a higher Ka value (and a lower pKa value).
Fragmentation
Adsorption
Receptors
Receptors are proteins that bind small ligands. The dissociation constant Kd is used as indicator of the affinity of the ligand to the receptor. The higher the affinity of the ligand for the receptor the lower the Kd value (and the higher the pKd value).