Hydrogen bond energy, experimental

The object of this work was to extend the field of application of the equation-of-state method. The method was applied to aqueous systems in conjunction with a model that treats water as a mixture of a limited number of polymers, an approach similar to that previously adopted for the carboxylic acids (2). Association is calculated by the law of mass action corrections for non-ideal behaviour are made by means the equation of state. A major problem of the method is the large number of parameters needed to describe the properties and concentrations of the polymers together with their interaction with molecules of other substances. The Mecke-Kemptner model (15) (also known as the Kretschmer-Wiebe model (16) and experimental values for hydrogen-bond energies were usecT for guidance in fixing these parameters. 

Table 8 Experimental, empirical and theoretical estimates of the hydrogen-bond energy of the bifluoride ion, A [HF(g) -F - FHF,g) ]/kJ mol". ...

In comparison with the general hydrogen bond energy (about 5 kcal/mol), this experimental value is small. This may be attributed to the fact that not all active sites are involved in the formation of the complex and moreover, this value is calculated from Eq. (35). Considering the relation,... 

In the calculation the water molecules were added without breaking the carboxylate/carboxylic group hydrogen bonds, but experimental evidence (13,14) shows the hydrogen bonds to be reduced to one half of their original number at the point of transition to a liquid crystalline phase and an evaluation of the energies involved was considered useful. 

Fig. 2.18 Examples of recognition models by hydrogen bonds with experimental association free energy-AC (in CDCI3, [kj/mol]) and -AC values (in italics) calculated with AAC incre-...

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