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. 

When the benzene ring contains a negative substituent the azido-group is eliminated by alkalis in the same way as is halogen, so that an alkali azide and a phenol are produced. 

Several types of corrosion inhibitors have been investigated in the last 20 years [53-55] these include calcium and sodium nitrites, sodium benzoate, sodium/potassium chromate, sodium salts of silicates and phosphates, stannous chloride, hydrazine hydrate, sodium fluorophosphate, permanganate, aniline and related compounds, alkalis, azides, ferrocyanide, EDTA and many chelating compounds. However, in terms of field practice and research data, nitrite-based compounds occupy a dominant position. 

Nas AsOs, does not react with the inorg salts of HNj, but with chloro- and iodoaxides it gives the alkali azide and halide and is ozidized to arsenate. Chlorine azide with silver azide forms Azino-Silver Chloride,... 

The alkali azidodithiocarbonates may be obtained by the action of carbon disulphide vapour on an aqueous solution of the alkali azide at 40° C.2 With a 1 per cent, solution of sodium azide the action proceeds quantitatively ... 

It was first prepd in 1923 by Turek on treating 2,4,6-trichloro-l,3,5-trinitrobenzene with an alkali azide in ale, acet or w soln. It can be obtained also from aniline by chlorination to sym-trichloro-aniline, followed by diazotization, treatment with ale to give sym-trichlorobenzene, nitration with mixed nitric-sulfuric acid to trinitrotrichloro-benzene and finally treatment with an ale soln of Na azide(Refs 3,5,6a 8)... 

An aq. soln. of hydrazoic acid was prepared by the Deutsche Gasgliihlicht-Auer Gesellschaft by adding oxalic acid and alcohol to a soln. of alkali azide, and removing the precipitate. L. M. Dennis and H. Isham prepared the anhydrous acid by slowly dropping dil. sulphuric acid (2 1) on to dry 0rj/A/>, fiece/lv,... 

It will be noted that the solubility of azides of the alkali metals increases as the at. wt. of the alkali metal increases and that their solubility in alcohol decreases with increasing at. wt. of the alkali metal. J. A. Cranston and A. Y. Livingstone showed that in the presence of platinum black, the alkali azide is decomposed ... 

Acetic acid-acetic anhydride, 85 Alkali azides, 79 Alkaline earth azides, 79 Alumino-oxalates, 36 Amalgams, 5 concentration of, 17 preparation of, 6 rare earth metal, 15 Ammonium nitrourethane, 69 Ammonium perrhenate, 177 Antimony oxyiodide, 105 Antimony triiodide, 104 Aquopentammino cobalti bromide, 187, 188... 

A similar strategy in aqueous media has now been applied to the nucleophilic substitution of alkyl halides or tosylates using readily available alkali azides, thiocyanates or sulfinates under microwave irradiation. The approach afforded safe and efficient preparation of azides, thiocyanates and sulfones (Scheme 23) (Ju et al., personal communications). 

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]. 

MeV protons and also by Co gammas by Oblivantsev et al. [110] and Boldyrev [111], and their radiation stabilities were compared to their thermal stabilities. Also determined were the range and loss of energy of 4.7-MeV protons in alkali azides. 

Thin films of CuNa have been prepared by Deb [28] using a displacement reaction between evaporated thin films of an alkali azide and copper(II) iodide. Thin films have also been prepared by reacting evaporated copper films with HN3 gas in the presence of water vapor [31]. 

Color centers can be produced in the alkali metal azide by ultraviolet light and ionizing radiation at low temperatures. The phenomenon has been of interest for some time since the defects produced are involved in the process of photochemical decomposition (cf. Chapter 7). In earlier studies [54a, b, c] purely speculative identifications of optical absorption bands with F, V, and aggregate F centers were made by analogy with the alkali halides. The most prominent visible absorption band in each case was attributed to the F center—a defect involving an electron trapped at an azide (N3) vacancy. In the case of NaNa, spin resonance [55] and recent point ion calculations [56] clearly point to the existence of a F center. However, in the case of KN3, spin-resonance studies [54a] point to the existence of molecular centers of type N2 (on low-temperature irradiation) and NJ (on room-temperature irradiation). Infrared absorptions [57] and Raman scattering [58] have been observed in the irradiated alkali azides, which can be correlated with modes associated with these defects. 

Optical absorption spectra of the alkali azides and of the ion in solution display common features (see below), suggesting that the ion s internal electronic transitions are not strongly perturbed by its environment. Further, the azide ion s internal vibrational modes do not differ appreciably from one ionic metal azide to another (see Chapter 4). This can be taken as further evidence that the ion s internal covalent bonding, and hence electronic structure, is relatively insensitive to its surroundings. Thus an understanding of the azide ion s electronic structure is a prerequisite to that of metal azide compounds. 

In an ionic environment, the azide ion has long been considered to be linear and, in alkali azides, symmetrical (see Chapter 3). Departures from linearity can be interpreted in terms of departures from ionic binding or crystal-field effects. 

The electronic structure of the azide ion can be observed in the XPS technique by studying the alkali azides. Studies of all the alkali azides have been reported by Sharma and coworkers [41], while information on individual alkali azides is available from the work of Siegbahn and coworkers [37], Wyatt and coworkers [28], Hollander and coworkers [15], and Barber and coworkers [42]. Since the results are in general agreement, only those of Sharma and coworkers [41] are discussed in detail. 

An optical absorption peak in the region of 5.4 eV (230 nm or 521 kJ/mole) was reported in azide ion solution spectra by Burak and Treinin [4], Closson and Gray [47], and McDonald et al, [17] by Deb [48] in a series of alkali azides and by Marinkas and Bartram [49] in BaNg. Deb [48] initially assigned the peak to an unspecified low-probability electronic transition of the isolated azide ion. More specific assignments have since been suggested to the transition... 

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