The Role of Solvent in the Partition of Procaine and p-Aminobenzoic Acid between Organic Solvent and Water

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The role of the solvent in the partition of procaine (PC) and its hydrolysis product, p-aminobenzoic acid (PABA), into various organic solvents was investigated from the viewpoints of the solvent polarity, the proton-donating and/or -accepting properties, and the solvation of the solute. The partition coefficients of PC and PABA in a pentanol (PeOH)-cyclohexane (CyH) mixture/water system gradually increased with increase of the mixing ratio of PeOH, but the change with the mixing ratio was not linearly correlated with the change of solvent polarity. The electrophilicity and/or nucleophilicity of the solvents did not greatly influence the partition of PC, whereas the partition of PABA varied with different solvent systems as follows ; nucleophilic solvents> amphiprotic solvents≫electrophilic solvents≫inert solvent. Furthermore, although it was ascertained that an appropriate solvating agent is required for the partition of a polar solute, the specificity was not always high due to the amphiprotic properties of PC and PABA. The solvation number and the extraction constant were obtained for PeOH, ethyl acetate, and chloroform as solvating agents for PC and PABA, and the nature of the solute-solvent interaction is discussed.
公益社団法人日本薬学会の論文
1985-11-25