Analysis of the solubility of betaine: calculation of descriptors and physicochemical properties

•Descriptors for betaine have been obtained from solubility data.•These descriptors can be used to predict further solubilities.•Partition coefficients and other properties can also be predicted.

We have previously constructed equations for the estimation of water–solvent partition coefficients of neutral molecules and of ions, in terms of properties or descriptors of the solute. We convert known solubilities of betaine in water and solvents into water–solvent partition coefficients and use the previous equations to determine descriptors for betaine. We show that equations for neutral compounds do not yield realistic results, but equations that include ionic terms allow descriptors for betaine to be determined. These indicate that betaine, although a very ‘polar’ molecule is not at all as polar as ion-pairs. From the determined descriptors, solubilities in further solvents and further water–solvent partition coefficients may be predicted.