Conglomerate salt

If ionic component X is the same in the conglomerate salt A+X , and the salt is dissociated into the ions, the solubility ratio of the racemate and active component Sr/Sa becomes equal to -f 2. The solubility phase diagram in this case is shown in Figure 4a, where the operation area becomes wider, and operations become easier. 

The Chilean nitrate deposits are located in the north of Chile, in a plateau between the coastal range and the Andes mountains, in the Atacama desert. These deposits are scattered across an area extending some 700 km in length, and ranging in width from a few kilometers to about 50 km. Most deposits are in areas of low rehef, about 1200 m above sea level. The nitrate ore, caUche, is a conglomerate of insoluble and barren material such as breccia, sands, and clays (qv), firmly cemented by soluble oxidized salts that are predominandy sulfates, nitrates, and chlorides of sodium, potassium, and magnesium. Cahche also contains significant quantities of borates, chromates, chlorates, perchlorates, and iodates. 

Conglomerate crystallization in the above case indicates that the inclusion approach may be further extended into the realm of the salt-type associates. Such an attempt is especially interesting due to the obvious role in enantiomer separation which relies heavily on the solubility difference of the enantiomeric salts under certain circumstances 137). 

A young Louis Pasteur observed that many salts of tartaric acid formed chiral crystals (which he knew was related to their ability to rotate the plane of polarization of plane-polarized light). He succeeded in solving the mystery of racemic acid when he found that the sodium ammonium salt of racemic acid could be crystallized to produce a crystal conglomerate. After physical separation of the macroscopic enantiomers with a dissecting needle, Pasteur... 

If the compound under consideration proves unsuitable for the entrainment method, either because it does not form a conglomerate or because the crystallization process itself is unsatisfactory, suitable derivatives, such as salts or esters, may be used for the resolution and then these derivatives reconverted to the original compound (Table 1). 

Although the submicellar model of the casein micelle readily explains many of the principal features and physicochemical reactions undergone by the micelles and has been widely supported, it has never enjoyed unanimous support and two alternative models have been proposed recently. Visser (1992) proposed that the micelles are spherical conglomerates of individual casein molecules randomly aggregated and held together partly by salt bridges in the form of amorphous calcium phosphate and partly by other forces, e.g. hydrophobic bonds, with a surface layer of K-casein. Holt (1992, 1994) depicted the casein micelle as a tangled web of flexible casein... 

The two salts may separate together, each retaining its individuality, so that each may be recognized, and the two varieties of crystals may be separated mechanically. Such a product is called a conglomerate or a mixture. 

Table 2 shows the result of examinations for the derivatives of a-methylbenzylamine. As can be seen, the salt of a-methylbenzylamine with cinnamic acid forms the crystals of a racemic mixture (Figure 5), and optical resolution by preferential crystallization can be possible in the form of this salt.8 Jacques and his co-authors have listed up 248 examples of organic conglomerates.1... 

While the frequency of conglomerate-forming systems is fairly small for organic compounds, a statistical analysis of more than 500 salts has demonstrated that the probability of observing spontaneous resolution is... 

Z. Bocskei, C. Kassai, K. Simon, E. Fogassy, D. Kozma, Racemic compound formation-conglomerate formation. Part 3. Investigation of the acidic salts of a-phenylethylamine by achiral dicarboxylic acids. Optical resolution by preferential crystallization and a structural study of (R)-a-phenylethylammonium hydrogen itaconate, J. Chem. Soc. Perkin Trans. 2 (1996) 1511-1515. 

K. Saigo, H. Kimoto, H. Nohira, K. Yanagi, M. Hasegawa, Molecular recognition in the formation of conglomerate crystal the role of cinnamic acid in the conglomerate crystals of 1-phenylethylamine and l-(4-isopropylphenyl)ethylainine salts. Bull. Chem. Soc. Jap. 

Resolutions of the racemates of helicenes have been carried out in different ways Helicenes, which often spontaneously crystallize as conglomerates, have been successfully separated into the enantiomers by Pasteurs mechanical method. Enantiomer separation using the diastereomeric salts prepared from 7-triphenylphosphonio-methyl[6]helicene and D-(—)-dibenzoyltartaric acid was successful, as was the separation of [6]helicene on polymers . 

In a similar manner, the racemates shown in Fig. 5.4 could be transformed into the corresponding conglomerates very easily by salt formation with achiral derivatizing agents [6]. These results indicate that salt formation with an achiral derivatizing agent is very effective for the transformation of an acidic or basic racemate into a conglomerate. 

In the next stage, we examined the crystal structures of the salts derived from 11 kinds of racemic primary amines and 24 kinds of achiral carboxylic acids in order to extract factors governing the formation of conglomerates. Among the combinations, 30 single crystals suitable for X-ray crystallographic analyses were obtained. Their X-ray crystallographic analyses revealed that most of the salt crystals can be classified into two types, 2i-column crystals and i-column crystals, on the basis of... 

Table 5.1 Derivatization of 1-phenylethylamine into a conglomerate upon salt formation with an achiral acid.

---