Historical Introduction

Aqueous solutions of alcohols have been for many years, and are still today, of considerable interest to a wide range of scientists and technologists. A low cost and miscibility with water of the lower members of the homologous series renders such mixtures useful as industrial solvent media for a variety of chemical reactions and for small and large scale separation processes. In particular, aqueous solutions of alcohols are often employed in the extraction and manipulation of labile materials such as proteins.

Physical chemists have long been intrigued by the eccentric properties of the mixtures, especially in the low concentration range. A review, published in 1966, and entitled ‘The structural properties of alcohol–water mixtures’ highlighted and tried to explain these peculiar features in the light of the then current ideas about the intermolecular nature of liquid water and solute–solvent hydrogen bonding. Emphasis was on thermodynamic properties with some excursions into spectroscopic, dielectric and transport phenomena. The general conclusion was that the predominant interaction, at least in dilute solutions, is not hydrogen bonding between the two species, but is determined primarily by the alkyl residue. The review posed more questions than it was able to answer but it stimulated considerable interest and activity among organic, physical and biochemists, as confirmed by the number of citations it achieved and the rapid growth in the number of publications describing investigations into alcohol–water mixtures.

In the light of developments over the past two decades, the time is ripe for a reappraisal of binary aqueous solutions of alcohols.