Titration calorimetry was used to measure equilibrium constants and standard molar enthalpies for the reactions of phenethylamine, ephedrines, and related substances with a-and /3-cyclodextrin. Changes in the chemical shifts A6 of both the ligand and cyclodextrin protons were measured with NMR. The thermodynamic results have been examined in terms of structural features of the ligand that affect these interactions such as the separation of the charge at an amino group and the aromatic ring, steric effects, the presence of additional functional groups (amino, hydroxy, methoxy, and methyl) attached to the aromatic ring, the presence and location of hydroxy group(s) on the ligand, changes in the chirality of the ligand, and the flexibility of the organic molecules attached to the aromatic ring. It was found that the values of thermodynamic quantities for these reactions in phosphate and acetate buffers were different. This difference is attributable to the presence of a hydrophobic alkyl group in the neutral acetic acid molecule and its interaction with the cyclodextrins. Also, there are significant differences in the thermodynamic quantities for the reactions of the chiral isomers of ephedrine and pseudoephedrine in their reactions with /3-cyclodextrin. A plot of the standard molar enthalpy vs the standard molar entropy for the reactions of these chiral isomers with a-and /3-cyclodextrin is linear; the relative order of the ephedrines and pseudoephedrines in the enthalpy-entropy plot is the same for the reactions of these substances with both a-and /3-cyclodextrin. NMR studies demonstrated that the magnitude of the upfield shifts of the cyclodextrin's H3 and H5 protons, A<5(H3) and A<5(H5), and their relative ratio, A<5(H5)/A<5(H3), can be used, respectively, as a measure of the complex stability and the depth of inclusion of the ligand into the cavity. The equilibrium constants determined by titration calorimetry correlate well with the changes in chemical shifts Ad determined by NMR.

http://xpdb.nist.gov/enzyme_thermodynamics/

The aqueous solubilities and octanol/water partition coefficients at 25 °C are determined for 12 chlorobenzenes and 16 polychlorinated biphenyls (PCBs) and for biphenyl by using the modified generator column method. These values are correlated with chlorine number and with either boiling point for the chlorobenzenes or the relative retention time of a polychlorinated biphenyl eluting from a gas-chromatographic (GC) column. Using differential scanning calorimetry (DSC), we have determined the melting points and enthalpies of melting for those compounds which are solid at room temperature. A correlation between the octanol/water partition coefficient and corrected aqueous solubility Is also presented, and the universality of the derived equation Is demonstrated.

This review contains recommended values of the thermodynamic and transport properties of the five and six membered ring carbohydrates and their phosphates in both the condensed and aqueous phases. Equilibrium data, enthalpies, heat capacities, and entropies have been collected from the literature. The accuracy of these data have been assessed, adjusted to 298.15 K and to a common standard state, and entered into a catalog of thermochemical reactions. The solution of this reaction catalog yields a set of recommended values for the formation properties of these substances. The volumetric data have also been critically evaluated. Recommended values are presented for standard state molar volumes and the temperature and pressure derivatives of the molar volume, i. e., the expansivity and the compressibility. The excess property data of aqueous solutions of these substances have been correlated to yield recommended values of the parameters of the virial expansion model used to represent the data. The transport data considered here includes both viscosity and diffusion data of aqueous solutions of the carbohydrates. The available phase diagram data and transition temperatures are summarized.

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