The Coextraction of Water into Nitrobenzene with Alkali and Alkaline Earth Metal Salts of 2,2′,4,4′,6,6′-Hexanitrodiphenylamine in the Presence of Several Crown Ethers and Cryptands

Abstract

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.

Evaluation of the Hydrophilic Property of Sodium Ion-pair Complexes with 3m-Crown-m Ethers (m = 5, 6) and Their Benzo-derivatives by Solvent Extraction

“…This is supported by the fact that the number (0.8) of water molecules co-extracted with Na(B15C5) + into nitrobenzene is somewhat smaller than that (1.1) with Na(B18C6) + . 13 Table 1, together with the component equilibrium constants, 1,2,14,15 which correspond to each system. It is clear that a difference in log Kex between the MnO4 -and tfa -extraction systems is mainly due to that in log KD,Na(15C5)A between them.…”

Hydration to Benzo-15-crown-5, Benzo-18-crown-6 and the Benzo-18-crown-6-Potassium Ion Complex in the Low-Polar Organic Solvents

“…The water molecule bound to the crown ether complex is that hydrated to the central metal ion. 14,17 It is well known that K + has the optimal size to fit into the cavity of the 18-membered ring crown ethers. Therefore, the small value of nH2O,KL for the KL + complex can be interpreted by the model that the B18C6 molecule conceals K + and thus the water molecule can not satisfactorily interact with K + in the complex.…”

“…[1][2][3][4][5][6][7][8][9][10] Particularly, in the solvent extraction study, since the solutes in the water-saturated organic solution are discussed, hydration of the solutes in the organic phase is a very important subject. It has been demonstrated that the water molecules are coextracted with the metal ions, [11][12][13][14] the metal complexes, [14][15][16][17] and the inorganic anions 2,3,[18][19][20] into the organic solvents, and the mean hydration numbers of these solutes in the organic phase were determined.…”

“…Iwachido et al 14 reported on the hydration number of the alkali and alkaline earth metal ions and of those complexes with several crown ethers or cryptands in the water-saturated NB. We reported on the hydration number of the alkali metal ions and barium ion complexes with the non-cyclic poly-(oxyethylene) compounds (POE compounds) or 18-crown-6 (18C6) in the water-saturated 1,2-DCE.…”

“…[1][2][3][4][5][6][7][8][9][10] Particularly, in the solvent extraction study, since the solutes in the water-saturated organic solution are discussed, hydration of the solutes in the organic phase is a very important subject. It has been demonstrated that the water molecules are coextracted with the metal ions, 11-14 the metal complexes, [14][15][16][17] and the inorganic anions 2,3,[18][19][20] into the organic solvents, and the mean hydration numbers of these solutes in the organic phase were determined.There have been numerous studies about the ion-pair extraction of the crown ether complexes; extractability and selectivity of the metal ions have been discussed by using the overall extraction equilibrium constant and its component equilibrium constants. 21,22 On the other hand, in recent years, hydration of the crown ether molecules and complexes has been also studied by both the theoretical 23-31 and experimental [32][33][34][35][36][37] approaches, but most of these studies were in aqueous solution.…”