Salt solubilization

Dietrich, Lehn and Sauvage recognized not only the possibility of enclosing a cation completely in a lipophilic shell, but they also recognized the potential for using such systems for activating associated anions. This is made particularly clear in a paper which appeared some years later One of the original motivations for our work on cryptates rested on their potential use for salt solubilization, anion activation and phase transfer catalysis . This particular application is discussed below in Sect. 8.3. 

It is worth mentioning at this point that according to Normant et al. (1975) simple polyamines such as tetramethylethylenediamine (TMEDA) are even more active than [2.2.2]-cryptand in the benzylation of acetates in acetonitrile under liquid-solid conditions. These authors suggested that the activity was due to salt solubilization by cation complexation and not to formation of a quaternary ammonium ion since the latter showed no activity. This statement, however, is not in line with the results of Cote and Bauer (1977), who were unable to detect any interaction between K+ and TMEDA in acetonitrile. Furthermore, Vander Zwan and Hartner (1978) found Aliquat 336 (tricaprylylmethylammonium chloride) to be almost as effective as TMEDA in this reaction (Table 30). It might well be, however, that in amine-catalysed benzylation reactions the quaternary salt formed in situ acts both as a reactant and as a phase-transfer catalyst, since Dou et al. (1977) have shown that the benzyltriethylammonium ion is a powerful benzylation agent. 

In the second type of chromatographic experiments chiral crown ethers of type [284] covalently attached to silica were equilibrated with solutions of racemic ammonium salts or amino-acid ester salts solubilized by addition of 18-crown-6 or alcohols in chloroform or dichloromethane (Table 66). The... 

A nonpolar solubilizate such as hexane penetrates deeply into such a micelle, and is held in the nonpolar interior hydrocarbon environment, while a solubilizate such as an alcohol, which has both polar and nonpolar ends, usually penetrates less, with its polar end at or near the polar surface of the micelle. The vapor pressure of hexane in aqueous solution is diminished by the presence of sodium oleate m a manner analogous to that cited above for systems in nonpolar solvents. A 5% aqueous solution of potassium oleate dissolves more than twice the volume of propylene at a given pressure than does pure water. Dnnethylaminoazobenzene, a water-insoluble dye, is solubilized to the extent of 125 mg per liter by a 0.05 M aqueous solution of potassium myristate. Bile salts solubilize fatty acids, and this fact is considered important physiologically. Cetyl pyridinium chloride, a cationic salt, is also a solubilizing agent, and 100 ml of its A/10 solution solubilizes about 1 g of methyl ethyl-butyl either m aqueous solution. 

Conversion of a cholic acid into glycocholate. Glycocholate is an example of a bile salt. The bile salts solubilize lipids in the small intestine so they can be degraded by lipases. 

The membrane-associated ECB deacylase of A. utahensis can be salt-solubilized, heat-treated, and purified to apparent homogeneity by a three-step chromatographic procedure. The deacylase is a heterodimer consisting of 63- and 18-20-kDa subunits. Except for salt stimulation, the deacylase has no external cofactor or metal ion requirement and has broad substrate specificity for the cyclic hexa-... 

Finally, anion activation can also be achieved by the complexation of the cation using suitable macro(poly)cyclic Hgand molecules [643]. Organic Hgands that contain enforced cavities of dimensions at least equal to those of the smaller cations (and anions) have been called cavitands [644]. Cation complexation by such macro(poly)cyclic ligands leads to dissociation of the ion pairs as well as to salt solubilization. Complex... 

It is worth mentioning, although this subject is not treated further, that living carbocationic polymerization can also be obtained in the absence of EDs by the use of common anions added to the charges in the form of common anion salts or simple salts solubilized by crown ethers [38-41]. The model is valid for these... 

Several authors have noted that the soluble salts of humic acid are surface active however, Wershaw et al. 21) were the first to demonstrate that soluble humic acid salts solubilize insoluble pesticides, such as DDT. Soluble humic salts are present in many soils, and they form in any organic soil on which alkaline fertilizers such as urea or anhydrous ammonia has been applied. Ballard (27) has shown in experiments with agricultural soils that DDT is solubilized by humic acid salts when the soils are fertilized with urea. 

Synthesis of oximes and amines. Copper salts solubilized in aqueous alkyl polyamines solvents have been found to promote the homogeneous reduction of nitroalkanes to oximes by CO at atmospheric pressure and 85 C in good yields and conversion(9. Catalysis is favoured by the use of copper salts of weak acids solubilized in alkylpolyamlnes solvents of pKa > 9.2. The suggested reaction path involves the formation of a solvated cuprous carbonyl complex, which by combination with the nitroalkane anion gives a copper-nitroalkane complex ... 

Figure 8.13 Experimental, ideal and predicted salt solubil ties using LIQUAC as a function of temperature...

This chapter attempted to show that receptors designed to bind specifically ion pairs might present numerous advantages in terms of affinity and selectivity. Often ion-pair receptors containing binding sites for both cations and anions display affinities for ion pairs that are enhanced relative to simple ion receptors. Unfortunately, in spite of their potential applications in various fields, such as salt solubilization, extraction, and membrane transport, the number of ion-pair receptors reported in the literature... 

The chemistry of cytochrome oxidase is not well known. From its spectrum the prosthetic group isolated by Negelein is similar to that of a hemin from the snail, Spirographis. This compound contains the structure l,3,5,8-tetramethyl-2-formyl-4-vinylporphin-6,7-propionic acid. A very similar compound has been crystallized recently from horse heart muscle, but its precise structure is not yet established. A green protein isolated from bile salt-solubilized particles has been... 

---