Halides, relative solubilities

It was necessary to assume that l-(4-pyridyl) pyridinium dichloride was formed without the formation of pyridinium chloride in the chloride reaction mixture, in order to account for the stoichiometries observed. The absence of the characteristic spectra of pyridinium chloride from samples of chloroform-soluble residues supported this assumption. However, for similar reasons it was necessary to conclude that pyridinium bromide was a product of the bromide reaction. The difference between the two reactions in this respect may be explained by the relative solubilities of the two halide salts of the protonated l-(4-pyridyl) pyridinium ion in pyridine. This point, however, was not pursued further in this investigation. 

The coverage has been limited to the applications of coordination compounds or of the coordination chemistry of relatively soluble ligands and metal species. Numerous chemical agents in photographic systems function by means of adsorption on silver halide grains and silver metal surfaces. Such chemical interactions lie outside the confines of coordination chemistry defined for this work and have not been discussed. 

Ldalide Complexes. Silver halides form soluble complex ions, AgX J and AgX , with excess chloride, bromide, and iodide. The relative stability of these complexes is 1 > Br > Cl. Complex formation affects solubility gready. The solubility of silver chloride in 1 AIHCl is 100 times greater than in pure water. 

Active catalysts for butadiene polymerization are obtained from aluminium alkyl halides and soluble Co and Co salts and complexes. The structure of the organic grouping attached to the cobalt is not important, but compounds most widely employed are acetylacetonates and carboxylic acid salts such as the octoate and naphthenate. The activity of the catalyst and structure of the polymer are affected by the groupings in the complex. Catalysts from aluminium trialkyls and cobalt salts other than halides are relatively unstable and give syndiotactic 1,2-polybutadiene. If halogens are present, e.g., from CoClj or CoBrj,... 

From relative solubilities (eqn. 20) of silver halides in DMSO and in water (Lnehrs e< ol., 1966) (cf. Table 5). From partial molar heats of solution of tetraethylammonium halides in DMSO and in water. (Arnett and McKelvey, 1966). 

The formation of the metal halide as a by-product limits the use of this method for the synthesis of reagents intended for further reactions. The relative solubilities of the organoalkali metal compounds and the metal halides formed in these reactions do not generally allow for easy separations. 

Relative solubilities of halides. The solubilities of silver halides in water decrease, going down the column of halogens in the periodic table ... 

A standard condition has been optimized for this reaction, in which the aryl amine is diazotized in 10 times its amount of acetic acid, followed by the addition of one equivalent of cuprous halide in hydrohalic acid. Under these conditions, the acetate salt of aryl amine is relatively soluble, and less froth and tarry material are formed during diazo transformation. In addition, chlorination, bromination, and iodonation of p-haloaniline to dihalobenzenes under such standard conditions give almost comparable average yields. Other modifications of this reaction include the formation of phenyl selenocyanate by the reaction with potassium selenocyanate, and aryl nitrile by the reaction with nickel cyanide. Moreover, this reaction has been extended to the preparation of phenyl thiocyanate, phenyl isothiocyanate and aromatic sulfonyl chloride. ... 

This result correlates with the relative stabilities of the product and starting material, which favor the chloroalkane. However, this equilibrium may be driven in the reverse direction by a simple trick Whereas all of the lithium halides are soluble in acetone, solubility of the sodium hahdes decreases dramatically in the order Nal > NaBr > NaCl, the last being virtually insoluble in this solvent. Indeed, the reaction between Nal and a primary or secondary chloroalkane in acetone is completely driven to the side of the iodoalkane (the reverse of the reaction just shown) by the precipitation of NaCl ... 

Other Group II halides are essentially ionic and therefore have relatively high m.p., the melts acting as conductors, and they are soluble in water but not in organic solvents. 

The alkali halides are relatively unreactive substances. They all display high solubility in water and quite low solubility in ethyl alcohol. 

The use of dimethylformamide (b.p. 153°) as a solvent and diluent oftai increases the yield materially. The vigour of the exothermic reaction which occurs with a relatively reactive aryl halide is moderated and, furthermore, the dimethylformamide is easily removed from the reaction product since it is water soluble. Aryl hah des which are inert under the usual Ullmann conditions do not react in the presence of dimethylformamide. 

In the case of molten salts, the functional electrolytes are generally oxides or halides. As examples of the use of oxides, mention may be made of the electrowinning processes for aluminum, tantalum, molybdenum, tungsten, and some of the rare earth metals. The appropriate oxides, dissolved in halide melts, act as the sources of the respective metals intended to be deposited cathodically. Halides are used as functional electrolytes for almost all other metals. In principle, all halides can be used, but in practice only fluorides and chlorides are used. Bromides and iodides are thermally unstable and are relatively expensive. Fluorides are ideally suited because of their stability and low volatility, their drawbacks pertain to the difficulty in obtaining them in forms free from oxygenated ions, and to their poor solubility in water. It is a truism that aqueous solubility makes the post-electrolysis separation of the electrodeposit from the electrolyte easy because the electrolyte can be leached away. The drawback associated with fluorides due to their poor solubility can, to a large extent, be overcome by using double fluorides instead of simple fluorides. Chlorides are widely used in electrodeposition because they are readily available in a pure form and... 

The auxiliary electrolyte is generally an alkali metal or an alkaline earth metal halide or a mixture of these. Such halides have high decomposition potentials, relatively low vapor pressures at the operating bath temperatures, good electrolytic conductivities, and high solubilities for metal salts, or in other words, for the functional component of the electrolyte that acts as the source of the metal in the electrolytic process. Between the alkali metal halides and the alkaline earth metal halides, the former are preferred because the latter are difficult to obtain in a pure anhydrous state. In situations where a metal oxide is used as the functional electrolyte, fluorides are preferable as auxiliary electrolytes because they have high solubilities for oxide compounds. The physical properties of some of the salts used as electrolytes are given in Table 6.17. 

Homogeneous polycrystalline membrane electrodes [see Fig. 2.10 (3)J. The relatively high electrical conductance of monoclinic / -Ag2S and its extremely low solubility product led to the development of halide and other metal ISEs with addition of silver sulphide. 

Similar reactions occur with all aliphatic halides and the rates of substitution are related to the degree of ionic character of the carbon-halogen bond. For preparation purposes, trityl bromide or propargyl bromide are more convenient than allyl bromide. The compounds obtained are listed in Table XI. They were obtained pure and characterized fully. Zr (allyl) 3Br and Zr(allyl)2Br2 are sufficiently soluble in toluene for polymerizations to be initially homogeneous. Their relative reactivities are listed in Table XI. In all cases hydrogen was used to reduce the molecular weight of the polymer formed. In this respect the polymer derived from Zr (allyl )3Br was more readily modified than that from Zr (allyl) 4, but in order to avoid... 

Many alkyl and aryl halides have very low solubilities in water, but they are miscible with each other and with other relatively nonpolar solvents. 

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