Functional groups enthalpy/entropy compensation

The relationship of thermodynamic functions of selective bonding of Hb to a series of carboxylic CP in the variation of the degree of ionization of carboxylic groups is expressed by the effect of enthalpy-entropy compensation (Fig. 18). The compensation effect of enthalpy and entropy components is the most wide-spread characteristic of many reactions in aqueous solutions for systems with a cooperative change in structure [78],... 

From the temperature dependence of the cmc as well as the enthalpy of demicellization it is possible to calculate the demicellization entropy and its temperature dependence using the Gibbs-Helmholtz relation AG AH - TAS. A plot of all three thennodynamic parameters as a function of temperature is shown in Figure 39 for the anionic surfactant sodium lauroyl-alaninate (SLA). It is clearly evident that the A(/-value for demicellization of SLA shows only a weak temperature dependence whereas the two tenns AH and TAS are strongly temperature dependent in a similar way. This type of enthalpy-entropy compensation is quite common for phenomena where changes in "hydrophobic hydration" are involved, because a considerable increase in heat capacity occurs when hydrophobic groups are exposed to water (see below) [ 124-131]. 

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