Principles and Practice of Chromatography - Factors Affecting the Magnitude of the Distribution Coefficient (K) > Hydrophobic and Hydrophilic Interactions > Page 29

The reasons for the introduction of the terms "lyophobic" (meaning fear of lye) and "lyophilic" (meaning love of lye) are a little more obscure. The terms originated in the early days of the soap industry when soap was prepared by boiling a vegetable oil with an alkaline solution obtained from leaching 'wood ash' with water. The alkaline product from the wood ash was a crude solution of sodium and potassium carbonates called "lye". On boiling the vegetable oil with the lye, the soap (sodium and potassium salts of long-chained fatty acids) separated from the lye due to the dispersive interactions between the fatty acid alkane chains and were thus called "lyophobic". It follows that "lyophobic", from a physical chemical point of view, would be the same as "hydrophobic", and interactions between hydrophobic and lyophobic materials are dominantly dispersive. The other product of the soap-making industry was glycerol, which remained in the lye and was consequently termed "lyophilic". Thus, glycerol mixes with water because of its many hydroxyl groups and is very polar and hence is a "hydrophilic" or "lyophilic" substance.

Hydrophobic and hydrophilic terms are extensively employed in biotechnology to describe the interactive character of the molecule as a whole. The use of a more general term to describe the interactive property of a biomolecule can be understood if one considers the character of a biopolymer, for example a polypeptide. The peptide will contain a large number of different types of amino acids, each having different interactive groups. All will exhibit polar interactions with the carbonyl and amide groups but each amino acid will contribute its own unique interactive character to the peptide. Thus, the terms hydrophilic and hydrophobic are more often used to describe the overall interactive character of a large molecule as opposed to the individual group interactions. Nevertheless they are basically alternative terms that have been adopted to describe polar and dispersive interactions respectively.