Sodium halides

Honea E C, Homer M L, Labastie P and Whetten R L 1989 Looalization of an excess eleotron in sodium halide olusters Phys. Rev. Lett. 63 394... 

Although the data for the silver halides suggest that silver(I) fluoride is likely to be more soluble than the other silver halides (which is in fact the case), the hydration enthalpies for the sodium halides almost exactly balance the lattice energies. What then is the driving force which makes these salts soluble, and which indeed must be responsible for the solution process where this is endothermic We have seen on p. 66 the relationship AG = — TAS and... 

The Fittig Reaction, in which sodium reacts with a mixture of an aryl and an alkyl halide, forming the sodium halide and the corresponding hydrocarbon ... 

Two mechanisms have been proposed for the Wurtz reaction (compare Section III,7) and for the Wurtz-Fittig reaction. According to one, sodium reacts with the alkyl halide to produce a sodium halide and a free radical, which subsequently undergoes coupling, disproportionation, etc. ... 

In order to detect these elements in organic compounds, it is necessary to convert them into ionlsable inorganie substanees so that the ionic tests of inoiganio qualitative analysis may be applied. This conversion may be accomplished by several methods, but the best procedure is to fuse the organic compound with metallio sodium (Lassalgne s test). In this way sodium cyanide, sodium sulphide and sodium halides are formed, which are readily identified. Thus ... 

Hexyl halide Sodium cyanide Hexyl cyanide Sodium halide... 

Table 3. Mutual Solubility of Sodium and Fused Sodium Halides...

Nitrogen and sodium do not react at any temperature under ordinary circumstances, but are reported to form the nitride or azide under the influence of an electric discharge (14,35). Sodium siHcide, NaSi, has been synthesized from the elements (36,37). When heated together, sodium and phosphoms form sodium phosphide, but in the presence of air with ignition sodium phosphate is formed. Sulfur, selenium, and tellurium form the sulfide, selenide, and teUuride, respectively. In vapor phase, sodium forms haHdes with all halogens (14). At room temperature, chlorine and bromine react rapidly with thin films of sodium (38), whereas fluorine and sodium ignite. Molten sodium ignites in chlorine and bums to sodium chloride (see Sodium COMPOUNDS, SODIUM HALIDES). 

Sodium halides, Sodium nitrate, Sodium nitrite. Sodium sulfates. Sodium sulfides. 

Figure 12.1 The solubilities of liquid sodium in the liquid sodium halides...

For the in situ preparation of the required arenediazonium salt from an aryl amine by application of the diazotization reaction, an acid HX is used, that corresponds to the halo substituent X to be introduced onto the aromatic ring. Otherwise—e.g. when using HCl/CuBr—a mixture of aryl chloride and aryl bromide will be obtained. The copper-(l) salt 2 (chloride or bromide) is usually prepared by dissolving the appropriate sodium halide in an aqueous solution of copper-(ll) sulfate and then adding sodium hydrogensulfite to reduce copper-(ll) to copper-(1). Copper-(l) cyanide CuCN can be obtained by treatment of copper-(l) chloride with sodium cyanide. 

Reaction with Alkyl Halides The gas inlet tube is replaced by an addition funnel, and 10 ml of HMPT is added rapidly with stirring. The mixture is cooled to 10-15°, and a solution of the alkyl halide (0.1 mole) in 20 ml of THF is added dropwise over a period of 30-40 minutes. The mixture is then heated to 40° for 2-3 hours. The thick white suspension of the sodium halide is cooled and dilute cold hydrochloric acid is carefully added until the mixture is clear. The organic layer is separated, and the aqueous layer is extracted three times with 20-ml portions of ether, the ethereal extracts then being combined with the organic material. The ethereal solution is washed twice with saturated sodium chloride solution and dried. The ether and THF are removed under reduced pressure (rotary evaporator), and the alkyne is distilled. 

The only parts of Fig. 5 which can meaningfully be described as solubility in a compressed gas are WX and XV. However, a very different situation arises if the saturated vapor pressure curve cuts the critical curve (M—N of Fig. 3). Figure 4 shows that this does not happen for the three sodium halides. The complete course of the critical curve is not known, but enough is known in the case of the sodium chloride system51 75 for it to be clear that it rises well above the maximum of the saturated vapor pressure curve. However, it is cut by the vapor pressure curves of less soluble salts such as sodium carbonate and sodium sulphate.40 87 The (p, T) projection of a system of the type water + sodium chloride is... 

These trends are apparent In the values of lattice energy that appear in Table Notice, for example, that the lattice energies of the alkali metal chlorides decrease as the size of the cation increases, and the lattice energies of the sodium halides decrease as the size of the anion increases. Notice also that the lattice energy of MgO is almost four times the lattice energy of LiF. Finally, notice that the lattice energy of Fc2 O3, which contains five ions in its chemical formula, is four times as large as that of FeO, which contains only two ions in its chemical formula. 

Salt-free ylides have been prepared from phosphonium chlorides and bromides by treatment with sodamide in refluxing THF. The sodium halide precipitates and is removed by filtration. Allylidene- and benzylidene-trimethylphosphoranes have been obtained as low melting distillable solids from the phosphonium chlorides and butyl-lithium in ether. The allylidenephosphorane on standing at room temperature slowly decomposed to give methylenetrimethylphosphorane. 

Fig. 26. Concentration of radical anions immediately after the laser flash and quantum yield as functions of the concentration of the respective sodium halide...

When an organic compound is heated with a mixture of zinc powder and sodium carbonate, the nitrogen and halogens are converted into sodium cyanide and sodium halides respectively, and the sulphur into. zinc sulphide (insoluble in water). The sodium cyanide and sodium halides are extracted with water and detected as in Lassaigne s method, whilst the zinc sulphide in the residue is decomposed with dilute acid and the hydrogen sulphide is identified with sodium plumbite or lead acetate paper. The t for nitrogen is thus not affected by the presence of sulphur this constitutes an advantage of the method. 

Applications Basic methods for the determination of halogens in polymers are fusion with sodium carbonate (followed by determination of the sodium halide), oxygen flask combustion and XRF. Crompton [21] has reported fusion with sodium bicarbonate for the determination of traces of chlorine in PE (down to 5 ppm), fusion with sodium bisulfate for the analysis of titanium, iron and aluminium in low-pressure polyolefins (at 1 ppm level), and fusion with sodium peroxide for the complexometric determination using EDTA of traces of bromine in PS (down to 100ppm). Determination of halogens in plastics by ICP-MS can be achieved using a carbonate fusion procedure, but this will result in poor recoveries for a number of elements [88]. A sodium peroxide fusion-titration procedure is capable of determining total sulfur in polymers in amounts down to 500 ppm with an accuracy of 5% [89]. 

Here, X and Y are halogens and R represents the remainder of the carbon skeleton. The reaction proceeds particularly well for the halogens chlorine and bromine, but much less so for fluorine, as the C—F bond is much stronger than either C—Cl or C—Br. However, the excited sodium halide, NaX1, is not the emitting species. Another collision between this molecule and another vapor-phase sodium atom is needed ... 

The resulting doublet sodium atom can then emit light at the sodium TMiric at 589 nm. With so many steps requiring atomic sodium, its concentration, which increases with temperature, significantly affects the chemiluminescent yield. Therefore, the temperature of the solid sodium must be tightly controlled. The excited sodium halide is readily quenched by ambient air molecules, so the system works best at reduced pressure. 

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.

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