ABSTRACT
The ionization of a compound depends on the strength of binding of the ionizable group to the core of the molecule, a property determined by the value of the dissociation constant. If the solubility of a compound is accompanied by degradation, the estimation of solubility becomes difficult and must be quoted with the degradant found. As compound supply is likely to be limited, only a few solvent systems can be investigated during initial solubility studies. Large organic molecules have a lesser aqueous solubility than smaller molecules. This is due to interactions between the nonpolar groups and water; solubility is dependent on the number of solvent molecules that can pack around the solute molecule. The measurement of partitioning is practical only if the compound shows some solubility; insoluble compounds are difficult to characterize and often prove less valuable anyway. The choice of the partitioning solvent can have significant effects on the results obtained and also on its relevance to biological systems.
