Other Alkali Azides

Caesium azide melts with a little decomposition (<1%) at 598 K. There is slow decomposition of the solid when large amounts of NiO are present [714], Observations on the photolyses of RbN3 and CsN3 have been discussed [715] with reference to the pyrolyses of other alkali azides. 

In this last reaction Na can be replaced by the azide NaN3 to give the same products. The normal oxides of the other alkali metals can be prepared similarly. 

The static dielectric constant (eo) of the alkali azides (cf. Table 11) is of the order of 6.5 while is 2.3. These values are of the same order as those of the alkali halides. Both the high and low frequency dielectric constants increase in the case of thallous. silver and cuprous azides. This is likely to be due to the increasing polarizibihty of the cations and a reflection of the decreasing ionicity of the lattices. The eo value for thallous azide and silver fulminate are however surprisingly high compared with the other azides. 

A useful method for the separation ofhydrazoic acid is by a column extraction technique using a mixed-bed ion-exchange resin, a strongly acidic resin in the [H form], and a weakly basic resin in the (OH" form). All cations and most anions are held on the column while hydrazoic acid runs through the column. Other cations and anions elute as water. Weak acids, e.g., boric, silicic, and carbonic will also run through the column. The technique has not been applied to the analysis of explosive azides however, it has been used for the analysis of alkali azides and for the preparation of standard solutions of hydrazoic acid [18]. 

Specific values for optical band gaps of alkali azides, proposed by Deb [48], are listed in Table IX. While deduced on the assumption of Wannier excitons, other approaches (Section C.2.b) yield similar values. Internal photoemission measurements [66] indicate the value 8.44 0.25 eV to hold for KN3 (see below). 

Other Azides. Preliminary absorption spectra of CUN3 [86], CdNe, and HgNg [121] have been reported by Deb. Thin films were prepared by the solid-solid reaction technique described for PbNg. Mixed crystal systems of metal azide halides were probably formed in the reactions, since the results differed for each combination of alkali azide-metal halide. An earlier CUN3 spectrum was interpreted by Evans and Yoffe [82] to indicate an w = 1 exciton, but here again that appears theoretically unsound (Section C.3.b). 

Azides react explosively or form other explosive azides when they come in contact with a number of substances. With acids, almost all metal azides react to form hydrazoic acid, which is dangerously sensitive to heat, friction or impact. Azides can react with salt solutions of many metals forming azides of those metals, some of which—especially, the heavy metal azides—are highly sensitive to friction and impact. The rates and yields of such reaction products would depend on the equilibrium constants and solubility products. For example, soluble alkali-metal azides can readily form lead or cadmium azide when mixed with a salt solution of lead or cadmium. The hazardous properties of some of the compounds of this class are discussed below. 

Direct incorporation of metals in microporous supports by adsorption of metal vapors is possible in the case of alkali metals which have high vapor pressures. In an early piece of work, Rabo et al. [66] reported that faujasites are able to sta-bihze neutral or ionic sodium clusters by exposing the carefully dehydrated zeo-Htes to sodium vapors under vacuum. The technique was later improved and extended to other zeoHtes and other alkali metals. Harrison et al. [67] found that Na + clusters were located in sodalite cages. Another technique consists of using the decomposition of sodium azide (NaNj) as a source of sodium vapor [68]. Xu and Kevan [69,70] achieved a detailed characterization of clusters prepared by these methods. Sodium clusters can even be loaded at room temperature merely by stirring the zeoHte powder with sodium or potassium in the solid state or in a solution of tetrahydrofuran or hexane [71]. 

Compounds of Tl have many similarities to those of the alkali metals TIOH is very soluble and is a strong base TI2CO3 is also soluble and resembles the corresponding Na and K compounds Tl forms colourless, well-crystallized salts of many oxoacids, and these tend to be anhydrous like those of the similarly sized Rb and Cs Tl salts of weak acids have a basic reaction in aqueous solution as a result of hydrolysis Tl forms polysulfldes (e.g. TI2S3) and polyiodides, etc. In other respects Tl resembles the more highly polarizing ion Ag+, e.g. in the colour and insolubility of its chromate, sulfide, arsenate and halides (except F), though it does not form ammine complexes in aqueous solution and its azide is not explosive. 

Alkyl azides are conveniently prepared from the reaction of alkali metal azides with an alkyl halide, tosylate, mesylate, nitrate ester or any other alkyl derivative containing a good leaving group. Reactions usually work well for primary and secondary alkyl substrates and are best conducted in polar aprotic solvents like DMF and DMSO. The synthesis and chemistry of azido compounds is the subject of a functional group series. ... 

Uses of Sodium Azide. The principal use of NaN, in the expl ind is in the prepn of alkali alkaline earth and other azides (Refs 37,38, 42,96,113,201,% others) (See Lead Azide, Plant Manufacture, etc). Meissner (Ref 44) used equiv quants of NaN, and a heavy metal salt, such as Pb acetate, for the continuous prepn of LA. Matter (Ref 33) found that NaN, was freed from carbonates by the addn of aq... 

A number of compounds of the types RBiY2 or R BiY, where Y is an anionic group other than halogen, have been prepared by the reaction of a dihalo- or halobismuthine with a lithium, sodium, potassium, ammonium, silver, or lead alkoxide (120,121), amide (122,123), azide (124,125), carboxylate (121,126), cyanide (125,127), dithiocarbamate (128,129), mercaptide (130,131), nitrate (108), phenoxide (120), selenocyanate (125), silanolate (132), thiocyanate (125,127), or xanthate (133). Dialkyl- and diarylhalobismuthines can also be readily converted to secondary bismuthides by treatment with an alkali metal (50,105,134) ... 

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