Enthalpy-entropy compensation, for

Fig. 4.—Enthalpy-Entropy Compensation for Alpha Cyclodextrin Inclusion-Complexes. [The guest identification numbers are as given in Table II.]...

Bustamante, P., S. Romero, A. Pena, B. Escalera, and A. Reillo, Enthalpy-entropy compensation for the solubility of drugs in solvent mixtures Paracetamol, acetanilide, and nalidixic acid in dioxane-water , J. Pharrn. Sci., 87, 1590-1596 (1998). 

Fig. 1. Enthalpy-entropy compensation for nonenzymatic prolyl isomerization (see Table I for literature references). 9, Proline-containing oligopeptides A, dipeptide , Gly-Gly-Lys-Phe-Pro. 1, Suc-Ala-Leu-Pro-Phe-pNA 2, Suc-Ala-Ala-Pro-Phe-pNA 3, Gly-Gly-Pro-Ala 4,N,N-dimethylacetamide 5,Suc-Ala-Trp-Pro-Phe-pNA 6, Suc-Ala-Gly-Pro-Phe-pNA 7, Gly-Pro 8, Ala-Pro 9, Val-Pro 10, His-Pro 11, Gly-Gly-Lys-Phe-Pro. Linear regression analysis of the data for compounds 1—6 yields a slope or critical temperature, T, of 232 29 K analysis of the data for compounds 7-11 yields = 212 27 K.

Fig. 4. Enthalpy-entropy compensation for PPI catalysis. Data taken from Table IV. , FKBP O, rhFKBP (Albers et ai, 1990) A, CyP.

Bustamante, C., Bustamante, P., 1996. Nonlinear enthalpy-entropy compensation for the solubility of phenacetin in dioxane-water solvent mixtures. J. Pharm. Sci. 85, 1109-1111. 

FIG U RE 10.4 Comparison between experimental (o) and calculated (solid lines) solubilities of phenacetin (S is the mole fraction of phenacetin) in the mixed solvent water/dioxane is the mole fraction of dioxane) at room temperature. The solubility was calculated using Equation 10.29. 1-activity coefficients expressed via the Flory-Huggins equation, 2-activity coefficients expressed via the Wilson equation. (From C. Bustamante, and P. Bustamante, 1996, Nonlinear Enthalpy-Entropy Compensation for the Solubility of Phenacetin in Dioxane-Water Solvent Mixtures, Journal of Pharmaceutical Sciences, 85, 1109. Reprinted from E. Ruckenstein, and I. L. Shulgin, 2003c, Solubility of Drugs in Aqueous Solutions. Part 2 Binary Nonideal Mixed Solvent, International Journal of Pharmaceutics, 260, 283, With permission from Elsevier.)... 

AS o (i.e., enthalpy-entropy compensation for micellization) to derive an equation similar to Equation 1.15 with an additional term C/T on the right-hand side. 

Jolicoeur, C., Philip, P.R. Enthalpy-entropy compensation for miceUization and other hydrophobic interactions in aqueous solutions. Can. J. Chem. 1974, 52, 1834-1839. 

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],... 

Guillaume et al. [69] presented a high performance liquid chromatographic method for an association study of miconazole and other imidazole derivatives in surfactant micellar using a hydrophilic reagent, Montanox DF 80. The thermodynamic results obtained showed that imidazole association in the surfactant micelles was effective over a concentration of surfactant equal to 0.4 pM. In addition, an enthalpy-entropy compensation study revealed that the type of interaction between the solute and the RP-18 stationary phase was independent of the molecular structure. The thermodynamic variations observed were considered the result of equilibrium displacement between the solute and free ethanol (respectively free surfactant) and its clusters (respective to micelles) created in the mobile phase. 

Enthalpy-entropy compensation has been investigated in reversed-phase HPLC with octylsilica stationary phase [77]. The compensation temperatures were determined for this system, and the results show that their change with the composition of the mobile phase is almost similar to that with octadecylsilica stationary phase. It can be concluded that the retention mechanisms of the separation of alkyl benzenes is the same in both systems with the mobile phase exceeding 20% water content. 

Enthalpy-entropy compensation, is expected to occur only if unity of mechanism exists. From the slope of the enthalpy vs entre y plot the so-called compensation temperature, which is chm teristic for the type of transformation under investigation, can be calculated. 

This temperature effect is the usual one for a regular or enthalpy-entropy compensated chromatographic separation, suggesting that the retention of each... 

Dunitz has analyzed entropy-enthalpy compensation semiquantitatively and has shown that it extends to all weak interactions.40 A weak interaction is a bond with a low vibrational frequency, which gives it an appreciable entropy (Chapter 2, section B4, Table 2.3). In general, a particle in a shallow, wide, energy well has more entropy than one in a deep, narrow well, and so there is a trade-off between enthalpy and entropy. For interactions of about 20 kJ/mol (5 kcal/mol) at 300 K, the changes in entropy and enthalpy by this process balance, and so there is nearly complete enthalpy-entropy compensation when the bond is broken. 

Ladbury JE (2004) Application of isothermal titration calorimetry in the biological sciences things are heating up . Biotechniques 37(6) 665-687 Leung DH, Bergman RG, Raymond KN (2008) Enthalpy-entropy compensation reveals solvent reorganization as a driving force for supramolecular encapsulation in water. 1 Am Chem Soc... 

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