Alkali and alkaline earth metal salts of 2,2′,4,4′,6,6′-hexanitrodiphenylamine (HND) were extracted into nitrobenzene in the absence or presence of several crown ethers or cryptands which differ from one another in hole size. The quantity of water transferred to the nitrobenzene phase was determined by means of the Karl-Fischer method. The NMR and near-infrared spectra show that the coextraction of water is caused by the hydration of the cations. The number of water molecules attached to the cations increases upon going from Cs+ (0.6) to Li+ (5.6) and from Ba2+ (10.5) to Ca2+ (13.0). The complexation between these cations and the crown ethers causes a clear decrease in the hydration number; e.g., in the 1:1 metal–crown ether complexes, more than half of the water molecules are removed, and in the 1:1 metal–cryptand complexes, less than one water molecule remains unremoved. The complexes of a 1:2 stoichiometry are also found; some are stable and carry virtually no water molecules. The number and type of donor atoms have no significant effect on the coextraction of water. The presence of fused benzo rings on the crown ether also has no influence on the number of water molecules.

Differential thermal analysis, differential scanning calorimetry, and measurements of the

The Hexyl(2,4,6,2′,4′,6′-hexanitrodiphenylamine) anion forms ion-pairs with alkali metal cations to some extent in an aqueous solution. The association constants of these ion-pairs were determined both in nitrobenzene by conductivity measurements and in water by the solvent extraction method. The association constants in nitrobenzene (KoMR) decrease in the following order: Li>Na>K>Rb>Cs. The plot of log KoMR against the ionic potential of the alkali metal ions was found to be linear. In nitrobenzene saturated with water, however, the constants vary from 2 to 4. In water the asscoiation constants (KaMr) vary from about 10 to 400, and the value increases as follows: Li<Na<K<Rb (<Cs). A plot of log KaMR against the reciprocal of the effective diameter of the hydrated alkali metal ions was found to be linear.

The distribution of alkali metal picrate complexes of macrocyclic polyether (dibenzo-18-crown-6) between water and benzene was investigated. The polyether-cation complexes were found to be of a 1:1 stoichiometry. The formation of 2:1 complexes was recognized for Rb and Cs in a large excess of the poiyether. The extractability of complex cation-picrate ion-pairs decreases in this sequence: K>Rb>Cs>Na>Li. The values of the extraction constants (logKex) were determined to be 4.65, 3.75, and 3.07 for K, Rb, and Cs compounds respectively. The thermodynamic quantities for the extraction process were calculated from the change in the extraction constants with the temperature. The extraction reactions are all exothermic, accompanied by an entropy decrease.

Complex formation constants of six crown ethers, benzo-12-crown-4, benzo-15-crown-5, benzo-18-crown-6, dibenzo-18-crown-6, dibenzo-21-crown-7, and dibenzo-24-crown-8 (B12C4, B15C5, B18C6, DB18C6, DB21C7, and DB24C8, respectively) with alkali and alkaline earth metal cations have been measured in aqueous solutions by capillary zone electrophoresis. The procedure involved the measurement of change in the electrophoretic mobility of the ligands upon increasing the metal ion concentration in the carrier electrolyte solution. A substantial increase in apparent electrophoretic mobility was observed for the crown ethers with increasing concentrations of the metal ions. The variations in increased electrophoretic mobility were attributed to the different stability of the complexes formed between the cations and the crown ether. The complex formation constants obtained with alkali metal cations were in the orders of: K+ > Na+ > Rb+ > Cs+ (B18C6), K+ > Na+ > Rb+ > Cs+ (DB18C6), Rb+ > Cs+ > K+ (DB21C7), and Rb+ > Cs+ (DB24C8); while with alkaline earth metal cations it was: Ba2+ > Sr2+ > Ca2+ (B18C6) and Ba2+ > Sr2+ (DB18C6). All the ligands examined showed no change in their apparent electrophoretic mobility upon changing Li+ and Mg2+ concentrations, indicating less reactivity with the cations. From the results obtained in this study, the electrophoretic method was proved to be preferable for analyzing the reactivity of the crown ethers and the selectivity toward metal cations.