binding coefficient binding coefficient in medicinal chemistry and pharmacology, a binding coefficient is a quantity representing the extent to which a chemical compound will bind to a macromolecule. the preferential binding coefficient can be derived from the kirkwood-buff solution theory of solutions. preferential binding is defined as a thermodynamic expression that describes the binding of the cosolvent over the solvent. this is in a system that is open to both the solvent and cosolvent. consequently, preferential interaction coefficients are measures of interactions that involve “solutes that participate in a reaction in solution.”