Hydrogen-bonded solutions, thermodynamic properties

The solute descriptors such as Jt, a, and P can be extracted from the hterature [2-5] and are in most cases empirically determined by spectroscopic measurements. Their calculation is based on the shift of absorption bands of the given solutes due to varying solvatochromic effects when the dipolar or hydrogen-bond donor /acceptor properties of the solvent mixture used for spectroscopy are altered. Hence, they are not true thermodynamic data. Abraham and co-workers also determined descriptors from GC retention data and octanol/water partition coefficients [6-9]. With the help of such descriptors, the so-called solvation equation (Eq. 5) can be set out [10,11] ... 

The reason is that classical thermodynamics tells us nothing about the atomic or molecular state of a system. We use thermodynamic results to infer molecular properties, but the evidence is circumstantial. For example, we can infer why a (hydrocarbon + alkanol) mixture shows large positive deviations from ideal solution behavior, in terms of the breaking of hydrogen bonds during mixing, but our description cannot be backed up by thermodynamic equations that involve molecular parameters. 

Abstract—This paper is an analysis of measurements of the thermodynamic properties of aqueous solutions of non-electrolytes, which has been made in order to establish both the relative strength of different kinds of hydrogen bonds in such solutions and the correlation between bond-strengths and the phase-behaviour of the solutions. The thermodynamic properties are compared with the results of statistical theories of solutions and with the properties of more simple solutions. 

Aqttbdus solutions are the most difficult to understand of all solutions of non-electrolytes and no quantitative theory of their thermodynamic properties has yet been proposed. This paper is a classification of such solutions and an attempt at a qualitative interpretation of their properties in terms of the strength and number of the hydrogen bonds formed between water and the solute. 

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