Acids and bases, definitions

For the sake of completeness, it is worthwhile to briefly discuss role of acid-base interactions in adhesion. In this context, the term acid refers to a Lewis acid (an electron acceptor) and a Lewis base (electron donor), rather than the more conventional acid and base definitions. The role of acid-base interactions in adhesion is discussed in detail by Lee [105]. 

However, the practice of investigations of acid-base equilibria consists in studies of the reactions with the transfer of definite particles (acid or base) in different solvents, irrespective of the fact whether they are prone to dissociation with the formation of given acid (base), or not. In order to give the most general formulation of the solvosystem concept we should divide the solvent in relation to the initially chosen definition of acids and bases (definition of acidic and basic particles). 

In the case of our initial and unsuccessful TLC attempts to enantioseparate the 5,/ -( )-ibuprofen and the 5,/ -( )-2-phenylpropionic acid antipodes [1-3], we kept our test samples for a longer period of time dissolved in 70% ethanol (and also in dichloromethane and physiological salt). Evidently, none of these solvents can be considered as a base or an acid, at least not in the spirit of the acid and base definitions introduced by Arrhenius. In other words, none of these solvents can catalyze or hamper transenantiomerization of the chiral APAs. However, the 70% ethanol solvent can easily be viewed as a weak ampholyte, able to simultaneously exert the catalytic and inhibiting effect on transenantiomerization of the chiral analytes considered. Perhaps, this perceptible ampholytic nature of 70% ethanol (combined with a change in viscosity of the APA solutions, as related to that of... 

---