Neutralization and solubility

A number of complexes of the type M(AA)2X2 are neutral and soluble in organic solvents. They are stereochemically non-rigid on an nmr time scale, that is they display nmr line broadening or collapse in accessible temperature ranges. Concommitant solvolysis problems can usually be avoided. The behavior shown is typified by the complexes Ti(P-diketone)2X2. The cis-configuration is invariably the stable one in solution, e.g. 6... 

Note All cobalt(I), cobalt(II) and cobalt(III) pincer carbene complexes are neutral and soluble in common organic solvents (THF, toluene, but not hexanes). 

An amino-acid, although insoluble in water (e.g., anthranilic acid), is usually soluble in excess of mineral acid in such a case it is important to make the solution only very slightly acid. This applies also to a mixture of a neutral and a basic substance, from which dil. HCl will extract an amino-acid the solution must then be carefully treated with NaOH to precipitate the amino-acid. 

The common treatment methods are acidification, neutralization, and incineration. When oxahc acid is heated slightly in sulfuric acid, it is converted to carbon monoxide, carbon dioxide, and water. Reaction with acid potassium permanganate converts it to carbon dioxide. Neutralization with alkahes, such as caustic soda, yields soluble oxalates. Neutralization with lime gives practically insoluble calcium oxalate, which can be safely disposed of, for instance, by incineration. 

Ethoxylation of alkyl amine ethoxylates is an economical route to obtain the variety of properties required by numerous and sometimes smaH-volume industrial uses of cationic surfactants. Commercial amine ethoxylates shown in Tables 27 and 28 are derived from linear alkyl amines, ahphatic /-alkyl amines, and rosin (dehydroabietyl) amines. Despite the variety of chemical stmctures, the amine ethoxylates tend to have similar properties. In general, they are yellow or amber Hquids or yellowish low melting soHds. Specific gravity at room temperature ranges from 0.9 to 1.15, and they are soluble in acidic media. Higher ethoxylation promotes solubiUty in neutral and alkaline media. The lower ethoxylates form insoluble salts with fatty acids and other anionic surfactants. Salts of higher ethoxylates are soluble, however. Oil solubiUty decreases with increasing ethylene oxide content but many ethoxylates with a fairly even hydrophilic—hydrophobic balance show appreciable oil solubiUty and are used as solutes in the oil phase. 

Zinc chloride melts at 275°C, bods at 720°C, and is stable in the vapor phase up to 900°C. It is very hygroscopic, extremely water-soluble, and soluble in organic Hquids such as alcohols, esters, ketones, ethers, amides, and nitrides. Hydrates with 1, 1.5, 2.5, 3, and 4 molecules of water have been identified and great care must be exercised to avoid hydration of the anhydrous form. Aqueous solutions of zinc chloride are acidic (pH = 1.0 for 6 M) and, when partially neutralized, can form slightly soluble basic chlorides, eg, ZnCl2 4Zn(OH)2 [11073-22-6] and Zn(OH)Cl [14031-59-5]. Many other basic chlorides have been reported (58). 

Emulsion Polymerization. In this method, polymerization is initiated by a water-soluble catalyst, eg, a persulfate or a redox system, within the micelles formed by an emulsifying agent (11). The choice of the emulsifier is important because acrylates are readily hydrolyzed under basic conditions (11). As a consequence, the commonly used salts of fatty acids (soaps) are preferably substituted by salts of long-chain sulfonic acids, since they operate well under neutral and acid conditions (12). After polymerization is complete the excess monomer is steam-stripped, and the polymer is coagulated with a salt solution the cmmbs are washed, dried, and finally baled. 

These acids are less stable, less soluble and less acidic than the corresponding sulfonic acids. The common impurities are the respective sulfonyl chlorides from which they have been prepared, and the thiolsulfonates (neutral) and sulfonic acids into which they decompose. The first two of these can be removed by solvent extraction from an alkaline solution of the acid. On acidification of an alkaline solution, the sulfinic acid crystallises out leaving the sulfonic acid behind. The lower molecular weight members are isolated as their metal (e.g. ferric) salts, but the higher members can be crystallised from water (made slightly acidic), or alcohol. 

The purity of (/-a-phenylethylamine-/-malate is not readily determined by its melting point or specific rotation, but rather by its massive crystalline form and solubility. The acid and neutral /-base-/-acid salts are much more soluble, and usually do not crystallize at all. 

Tetrahydrostrychnine, CgjHggOgNg. HgO. This substance, also formed by the electrolytic reduction of strychnine, crystallises from alcohol in prisms, m.p. 202°, gives colour reactions of the strychnidine type, and yields both neutral and acid salts the hydrochloride, B. HCl, occurs in small needles readily soluble in water and the dihydriodide, B. 2HI. 2HjO, in pyramidal crystals. The base yields an amorphous nitrosoamine, the hydrochloride of which crystallises from warm water in lustrous, yellowish prisms. It also furnishes a crystalline monoacetyl derivative, and on heating with hydrochloric acid or phosphorus oxychloride is dehydrated to strychnidine. 

The qualitative thermodynamic explanation of the shielding effect produced by the bound neutral water-soluble polymers was summarized by Andrade et al. [2] who studied the interaction of blood with polyethylene oxide (PEO) attached to the surfaces of solids. According to their concept, one possible component of the passivity may be the low interfacial free energy (ysl) of water-soluble polymers and their gels. As estimated by Matsunaga and Ikada [3], it is 3.7 and 3.1 mJ/m2 for cellulose and polyvinylalcohol whereas 52.6 and 41.9 mJ/m2 for polyethylene and Nylon 11, respectively. Ikada et al. [4] also found that adsorption of serum albumin increases dramatically with the increase of interfacial free energy of the polymer contacting the protein solution. 

Rh(N02)6 is of some importance in the traditional extraction of rhodium. Impure RI1CI3 is neutralized and treated with NaN02 Na3Rh(N02)6 is soluble under these conditions (though base metals precipitate), but when ammonium chloride is added, (NH4)3Rh(N02)6 precipitates. The potassium salt is similarly relatively insoluble. All these salts are believed... 

Neutral salt-soluble collagen as well as add-soluble collagen show a CD spectrum (Fig. 8) having bands at 198 nm, 0 = -53 (MX) (deg cm2 dmol-1), and at 223 nm, 0 = 7500 (deg cm2 dmol-1), the ratio between both being 7 1. Pysh has calculated the CD spectra of a-helix, -structure, polyproline I and II127 ... 

Fig. 37. Dependence of the thermodynamic parameters AH and AS of triple-helix formation on the imino acid content of the peptides (obtained by cleavage of calf skin-type I collagene with cyanogene and subequent isolation by column chromatrography)3) and of the native neutral salt-soluble skin collagene of various animals. The entropy values are denoted by dotted lines...

To keep product yield at a maximum it is important that the solubility of product in the spent acid be kept to a minimum. This also facilitates removal of traces of product from the spent acid so that it can be either fortified and reused, reused to make lower nitro compds, or neutralized and discharged as non-polluting waste material... 

---