Enthalpies of acid-base interactions

For decades such adsorption had been assumed to involve dipole interactions and interacting sites were termed "polar." It is quite clear in the above studies that dipoles in the polymers and in the solid surfaces do not contribute measurably to adsorption. Even from carbon tetrachloride, the solvent most favorable to adsorption, the amount of basic polymer (PMMA) that adsorbed onto basic calcium carbonate was only 2.5% of the amount that adsorbed on the same area of silica surface. Similarly, the amount of acidic polymer (CPVC) that adsorbed onto the acidic silica from any of the six solvents was less than 0.2% of the amount that adsorbed from carbon tetrachloride or dichloromethane onto the same area of basic calcium carbonate. It is concluded that adsorption of organic acids or bases from neutral organic solvents onto inorganic solids is governed entirely by acid-base interactions and is quite independent of dipole phenomena. It is therefore proposed that heats of adsorption are actually enthalpies of acid-base interaction and should therefore be subject to the Drago correlation ... 

A four-parameter equation for predicting the calorimetric enthalpies of acid-base interactions, —Ai/ab, in neutral solvents, proposed by Drago et al. [146], with spectroscopically determined shifts of the OH stretching frequency of phenol when interacting with a variety of bases of dilute solutions in carbon tetrachloride and tetrachloroethylene. 

XPS is emerging as very precise method for evaluating acid-base interactions based on the works by Chehimi et al. There is very good correlation between XPS chemical shift and the change in exothermic enthalpy of acid-base interaction. Drago s equation is used for data interpretation ... 

A new approach to the problem is based on the concept of acid-base interac-tions. The theory takes into account the existence of acid or base properties of the filler surface and pol3rmer adhesives. For example, poly(vinyl chloride) or other chlorinated pol3uners have acid properties and are capable of interaction with fillers or pol3uners with basic properties (Si02, CaCOs, polyesters etc). The enthalpy of adsorption of polymer with base properties B from one neutral solution on acid surfaces A is really the enthalpy of acid-base interaction AH ... 

The exothermic enthalpy of acid-base interaction (in kcal moF ) can be predicted from Drago s equation I13]. 

Fowkes and Mostafa relate to the enthalpy of acid-base interaction from equation (15) by... 

Spectroscopic measurements Fowkes approach Fowkes has proposed that for specific functional groups involved in acid-base interaction, the enthalpy of acid-base adduct formation is related to the infrared frequency shift, Av, of its absorption band according to the following equation ... 

The influence of a solvent complicates any understanding of acid-base interactions in solutions. The calculation of aqueous acidity constants would require the calculation of the free enthalpy of solvation of the acidic site, conjugate base, and proton, in addition to the gas-phase term for the change of free enthalpy during deprotonation and, of course, all entropy terms. While the entropy o/deprotona-tion is nearly independent of the acid-base couple, the free enthalpy of solvation can be obtained only with difficulty from molecular dynamics calculations [13]. 

In fact, since and coefficients are expressed in terms of enthalpy units, the parameter A can be considered equal to the variation of the enthalpy for acid-base interactions (-AH h) t the fibre-matrix interface. Moreover, Fowkes and Mostafa [2] have suggested that the contribution of the polar interactions to the thermodynamic work of adhesion could be generally neglected compared to both dispersive and acid-base contributions. They have also considered that the acid-base component of the adhesion energy can be related to the variation of enthalpy corresponding to the... 

Fowkes was one of the first people to emphasize the importance of acid-base interactions in the context of adhesion. The volume of papers collected to honour his 75 birthday provides an important source of detailed information. Fowkes has argued that the acid-base component of the work of adhesion can be related to the molar enthalpy, for the acid-base reaction by... 

From the above discussion of Drago s equation, the work of acid-base interaction for a pair of molecules is a function of the enthalpy of the interaction. 

Another approach for describing solid-liquid interactions at an interface has been proposed, based on computations of acid-base interactions. An empirical correlation exists for the enthalpy of mixing when an acid, i.e., electron pair acceptor, and a base, i.e., electron pair donor, are mixed... 

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