Halides of alkali metals

All halides of alkali metals, except Li, are practically insoluble in pyridine this situation is... 

A special flux consisting of the halides of alkali metals with the addition of sodium and aluminium fluorides was employed both to protect the aluminium melt from oxidation and to pre-heat the specimen to the required temperature. First, the flux was melted in a 26 mm inner diameter alumina crucible. Melting started at about 350°C. The height of the flux column was around 15 mm. Aluminium pieces were then melted under the flux layer. The amount of aluminium taken was equivalent to a volume of... 

Since oxides and halides of alkali metals possess sufficient stability under the experimental conditions, the possibility of determining the parameters of... 

Reaction over Base Catalysts. - Masada et al. reported a detailed study on the reaction with methyl propionate over silica-supported various base catalysts. The reaction is conducted in the presence of methanol but in the absence of water vapor. HCHO free from water is obtained by the thermal decomposition of cyclohexanol-hemiformal which was previously prepared from formalin and cyclohexanol. The performances of catalysts are summarized in Table 8. The KOH catalysts are more active than the CsOH catalysts, although the selectivity to methyl methacrylate is lower. Incorporation of halides of alkali metal into the KOH catalyst improves the yield of methyl methacrylate, though the halides by themselves are inactive for the reaction. The best results are obtained with a KOH (1.5 percent) + Csl (0.5 percent) on silica catalyst. The single-pass yield of methyl methacrylate reaches about 59 mol% based on the charged HCHO with a methyl propionate/HCHO/ methanol molar ratio of 10/1/10. It is also found that the selectivity of methyl propionate to methyl methacrylate is very high, nearly 100 mol%. The best support is found to be silica gel. No catalytic activity is observed with the alumina-supported catalysts. 

In most processes recirculation of the stable feed hydrocarbon is maintained and the reactive olefin is fed into the recycling stream sometimes at several points. Thus, the concentration of olefin is always low and polymerization reactions are minimized. The alkylation reaction is favored by high pressures and low temperatures. However, in order to accomplish the reaction without catalysts, temperatures of 900 to 975 F are required.Polymerization also occurs rapidly at such temperatures, and hence the olefin concentration must be kept low. Thermal alkylation is conducted at 3,000 to 8,000 psig, whereas by means of catalysts such as sulfuric acid, boron fluoride, - aluminum chloride, double halides of alkali metals with aluminum, and hydrogen fluoride, pressures less than 500 psi and temperatures ranging from 450°F down to below zero may be employed. Sulfuric acid was widely used early in World War II as a catalyst in commercial installations, and a revival of interest has occurred since 1951. The process operates at 30 to 60 F for butenes and at substantially atmospheric pressure. The hydrofluoric acid process also proved during World War II to be a highly successful process, but only... 

Halides. Indium trichloride [10025-83-8] InCl, can be made by heating indium in excess chlorine or by chlorinating lower chlorides. It is a white crystalline soHd, deUquescent, soluble in water, and has a high vapor pressure. InCl forms chloroindates, double salts with chlorides of alkaLi metals, and organic bases. 

Figure 4.3 Melting point and boiling point of alkali metal halides.

The compounds can therefore be used as nonaqueous ionizing solvent systems (p. 424). For example the conductivity of ICl is greatly enhanced by addition of alkali metal halides or aluminium halides which may be considered as halide-ion donors and acceptors respectively ... 

By incorporation of alkali metal halides in the reaction mix, materials of composition M4-[MfiXig] can be produced in which each MgXn unit has a further six X atoms attached to its apices, so forming discrete clusters. 

Fluorination of a mixture of alkali metal halide and an appropriate ruthenium or osmium halide affords cream MRuF6 (M = alkali metal, Ag /ieff = 3.5—3.8 /l b) or white MOsF6 ... 

The saline hydrides are white, high-melting-point solids with crystal structures that resemble those of the corresponding halides. The alkali metal hydrides, for instance, have the rock-salt structure (Fig. 5.39). 

Experimental data show that at the usual concentrations (10 to lOM), most salts and also the hydroxides of alkali metals are strong electrolytes. This is true also for some inorganic acids HCl, HCIO4, and others. Weak electrolytes are the organic acids and the hydroxides of metals other than alkah. Few electrolytes of the intermediate type (with moderate values of a) exist in particular, certain transition-metal halides such as ZnClj, Znl2, and CdCl2 are in this category. 

Alternatively, esterification of carboxylic acid can be carried out in aqueous media by reacting carboxylic acid salts with alkyl halides through nucleophilic substitutions (Eq. 9.10).20 The reaction rate of alkyl halides with alkali metal salts of carboxylic acids to give esters increases with the increasing concentration of catalyst, halide, and solvent polarity and is reduced by water. Various thymyl ethers and esters can be synthesized by the reactions of thymol with alkyl halides and acid chlorides, respectively, in aqueous medium under microwave irradiation (Eq. 9.11).21 Such an esterification reaction of poly(methacrylic acid) can be performed readily with alkyl halides using DBU in aqueous solutions, although the rate of the reaction decreases with increasing water content.22... 

The choice of the fill material initiating the discharge is very important. Together with a standard mercury fill it is often desirable to incorporate an additive in the fill material that has a low ionization potential [38, 39]. One category of low-ioniza-tion-potential materials is the group of alkali metals or their halides (Lil, Nal) but some other elements, such as Al, Ga, In, T1 [40, 41], Be, Mg, Ca, Sr, La, Pr, or Nd [23, 37, 42], can be used. 

Table 7.1 Ionization Potentials and Heats of Sublimation of Alkali Metals and the Heats of Formation of Alkali Metal Halides. ...

Dithiophosphato metal complexes are usually prepared by metathesis of metal halides with alkali metal or ammonium salts. A convenient method uses the redox reaction of his th iophosphory 1 )d is ulfanes (RO)2(S)PSSP(S)(OR)2, with metal species in low oxidation states resulting in the insertion of the metal into the sulfur-sulfur bond.24 Recently it was used for the synthesis of long alkyl chain, liquid platinum(II) dithiophosphates25 and for the synthesis of Ru (CO)2[S2P(OPr%]2 from Ru3(CO)i2 with (Pr 0)2(S)PSSP(S)(0Pr,)2.26... 

Metal dithiophosphinato complexes are usually prepared by metathesis of metal halides with alkali metal or ammonium dithiophoshinates, but can also be conveniently prepared by reactions of /i .v(thiophosphinyl)disul fanes, R2(S)PSSP(S)R2, with metal species.87 The electrochemical oxidation of metals in acetonitrile solution, in the presence of diphenylphosphine and sulfur affords M(S2PPh2)2 (M = Co, Zn, Cd),88 but this is not a preparative method. 

Figure 7.4 Thermodynamic data needed in evaluation of the enthalpy of formation of MX(s). (a) Lattice enthalpy of sodium halides (b) lattice enthalpy of alkali iodides (c) electron gain and dissociation enthalpies of halides (d) ionization and atomization enthalpies of alkali metals.

The sample is dissolved in 1-5 % of the solvent and it is then placed in a solution cell consisting of transparent windows of alkali metal halides. A second cell containing pure solvent is then placed in the path of reference beam to cancel out solvent interferences. 

Association and mobilities are related in a complex way to the bulk properties of the solvent and solute. These properties include the charge density and distribution on the ions and the Lewis base properties, the strength and nature of the solvent molecule dipole, the hydrogen-bonding capability, and the intermolecular structure of the solvent. Some correlations can be made on the basis of mobility and association trends in series such as the halides and alkali metals within a single solvent others can be drawn between solvents for a given ion. It appears that conductance measurements provide a clear measure of the sum of ion-solvent interactions, but that other techniques must be used in conjunction with conductance if assessments of individual contributions from specific factors are to be made. 

As elaborated earlier for the behavior of hydrogen halides and alkali metal halides in water, the ionization of many other metal halides follows the same... 

On looking into the literature to see whether this value of d(ff) = 0.28 A is meaningful, it was found [1] that this is the value suggested by Pauhng [8] to account for the radius of H in the partially ioitic bonds in hydrogen halides and in alkali metal hydrides The author then used this value of d(H+) = 0.28 A to estimate the radii of alkali metal ions from the observed bond distances d(MH) j in the metal hydrides, MH. It was a pleasant surprise to find that,... 

This conclusion falls in line with the fact that the anion radical could neither be detected after collision of the parent halide with alkali metal atoms in the gas phase (Compton et ai, 1978) nor upon y-irradiation in apolar or weakly polar solid matrixes at 77 K by esr spectroscopy (Symons, 1981). However, these observations are not absolute proofs that the anion radicals do not exist they might exist and be too short lived to be detectable. On the other hand, the reaction medium and the driving force conditions are quite different from those in the electrochemical experiments, which rendered necessary an independent investigation of the problem in the latter. 

The reaction of alkali metal phosphides with appropriate halides, sultones or cyclic sulfates is a generd method for preparation of a variety of tertiary phosphines useful in aqueous organometallic catalysis. These... 

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