Azides hydrogen

In general, it can be said that gaseous hydrogen azide will invariably explode when thermally shocked or when sudden pressure changes occur. The gas may 

Liquid hydrogen azide also explodes on thermal or mechanical shock [31]. The freshly prepared liquid reportedly does not explode spontaneously, but tends to do so upon aging [31]. Solid hydrogen azide explodes likewise on thermal and mechanical shock spontaneous explosions are not reported. 

There are several methods for making hydrogen azide, which are all based on the simple equation 

Sodium azide, at elevated temperature, is reacted with a suitable acid, and gaseous hydrogen azide is evolved. The acid must not chemically attack the azide ion, and the reactants must be less volatile than HN3. Suitable acids are sulfuric, phosphoric, phosphorous, oxalic, perchloric, fluosilicic, stearic, and palmitic acids. 

The use of concentrated sulfuric acid in this process would eliminate water, but is not recommended as some reaction with the azide is inevitable, leading to impurities such as hydroxylamine [32] and sulfur dioxide [33]. If concentrated H2SO4 is chosen, the procedure should be conducted in vacuo, the gases passed onto a cold finger, and the deposit allowed to warm up to remove the lower boiling impurities [34]. 

Aqueous solutions of HN3 were first prepared in 1890 by T. Curtius who oxidized aqueous hydrazine with nitrous acid  

Other oxidizing agents that can be used include nitric acid, hydrogen peroxide, peroxydisulfate, chlorate and the pervanadyl ion. The anhydrous 

Similar differences are found for organic azides (e.g. MeN3). In ionic azides (p. 417) the N3 ion is both linear and symmetrical (both N-N distances being 116 pm) as befits a 16-electron species isoelectronic with CO2 (cf. also the cyanamide ion NCN, the cyanate ion NCO, the fulminate ion CNO and the nitronium ion N02 ). 

Aqueous solutions of HN3 are about as strongly acidic as acetic acid  

Numerous metal azides have been characterized (p. 417) and covalent derivatives of non-metals are also readily preparable by simple metathesis using either NaN3 or aqueous solutions of 

For an extensive review of the chemistry of the alkali amides, see Berg- 

Aqueous solutions of hydrogen azide are readily obtained by treatment of sodium azide f with sulfuric acid. Since pure hydrogen azide is extremely explosive, and since its vapors produce most unpleasant physiological effects, it is advisable to use care in its preparation. Especially is the treatment of dry sodium azide, or of a cold solution, with sulfuric acid to be avoided, since this results in the formation of pure hydrogen azide (b. 37°C.) which may condense to the anhydrous liquid or to a highly concentrated aqueous solution, both of which are extremely explosive. 

In addition to the method outlined under procedure A, hydrazoic acid may be prepared by the action of oxalic1 or fluosilicic acids2 upon solutions of sodium azide or by the treatment of barium azide solutions with dilute sulfuric acid. A method involving the action of perchloric acid upon potassium azide has also been proposed. However, subsequent distillation of the filtrate, after removal of the precipitated potassium perchlorate, is necessary to prepare pure hydrazoic acid. Pure hydrazoic acid has also been obtained by the oxidation of hydrazine in acid solution by hydrogen peroxide.3-  

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Nitrogen, phosphorus and arsenic form more than one hydride. Nitrogen forms several but of these only ammonia, NHj, hydrazine, N2H4 and hydrogen azide N3H (and the ammonia derivative hydroxylamine) will be considered. Phosphorus and arsenic form the hydrides diphosphane P2H4 and diarsane AS2H4 respectively, but both of these hydrides are very unstable. 

Acids and -ide Anions. Acids giving rise to the -ide anions (Sec. 3.1.2.2) should be named as hydrogen. . . -ide for example, HCl, hydrogen chloride HNj, hydrogen azide. 

Heavy water, see Hydrogen[ H] oxide Heazlewoodite, see rn-Nickel disulfide Hematite, see Iron(III) oxide Hermannite, see Manganese silicate Hessite, see Silver telluride Hieratite, see Potassium hexafluorosilicate Hydroazoic acid, see Hydrogen azide Hydrophilite, see Calcium chloride Hydrosulfite, see Sodium dithionate(III)... 

Putrescine dihydrochloride has been prepared by the Hofmann degradation of adipamide 3.. s by the Curtius degradation of adipyl hydrazide through the urethane by the Curtius degradation of adipyl azide obtained from adipyl chloride and sodium azide by the Schmidt degradation of adipic acid with hydrogen azide by the reduction of succinonitrile, succinaldoxime, or 7-phthalimidobutyronitrile with sodium and from N-ben-zoyl-7-iodobutylamine ... 

Nitrogen forms more than 20 binaiy compounds with hydrogen of which ammonia (NH3, p. 420), hydrazine (N2H4, p. 427) and hydrogen azide (N3H, p. 432) are by far the most important. Hydroxylamine, NH2(OH), is closely related in structure and properties to both ammonia, NH2(H), and hydrazine, NH2(NH2) and it will be convenient to discuss this compound in the present section also (p. 431). Several protonated cationic species such as NH4+, N2H5+, etc, and deprotonated anionic species such as NH2 , N2H3 , etc. also exist but ammonium hydride, NH5, is unknown. Among... 

Consistent with this NNO can be made from NH4N03, and N NO from NH4 N03. Alternative preparative routes (Fig. 11.9) are the reduction of aqueous nitrous acid with either hydroxylamine or hydrogen azide ... 

Isothiocyanates react with hydrogen azide to give 5-alkyl- (or -aryl-)-aminothiatriazoles [Eq. (3)]. This reaction is of... 

The free acid, l,2,3,4-thiatriazole-5-thiol, may be prepared from hydrogen azide and carbon disulfide, but the simplest way to obtain the acid is to treat a chilled solution of the sodium salt with concen-... 

A different reaction takes place between an ethereal solution of the disulfide and hydrogen azide this reaction proceeds according to Eq. (15). Probably the principal step of this reaction is the spontaneous decomposition of the disulfide into nitrogen, sulfur, and... 

Hydrogen azide in the pure state, which is highiy endothermic, detonates vioientiy. 

In the presence of acid, sodium azide leads to hydrogen azide, the dangerous behaviour of which has already been mentioned. 

Metallic cyanides, sodium azide and hydrogen azide form explosive mixtures with nitric acid. 

Surprisingly it is thermally stable to 300°C, (cadmium azide is very heat sensitive) but is hygroscopic and very readily hydrolysed to explosive hydrogen azide. 

It explodes on exposure to mechanical or thermal shock. Care is necessary during preparation to eliminate hydrogen chloride from the precursory acid chloride, to prevent formation of hydrogen azide. 

An ethereal solution of some 100 g of the crude nitrile was allowed to spontaneously evaporate and crystallise. The crystalline slurry so produced exploded violently without warning. Previously such material had been found not to be shock-sensitive to hammer blows, but dry recrystallised material was very shock-sensitive. Traces of free hydrogen azide could have been present, and a metal spatula had been used to stir the slurry, so metal azides could have been formed. See Other CYANO COMPOUNDS, ORGANIC AZIDES... 

A violent explosion occurred during vacuum distillation of 4-chlorophenyl isocyanate, prepared by Curtius reaction from the azide. It was found by IR spectroscopy that this isocyanate (as well as others prepared analogously) contained some unchanged azide, to which the explosion was attributed. The use of IR spectroscopy to check for absence of azides in isocyanates is recommended before distillation [1], Subsequently, the explosion was attributed to free hydrogen azide, produced by hydrolysis of the unchanged acyl azide [2],... 

A solution, prepared by mixing saturated solutions of cadmium sulfate and sodium azide in a 10 ml glass tube, exploded violently several horns after preparation [1], The dry solid is extremely hazardous, exploding on heating or light friction. A violent explosion occurred with cadmium rods in contact with aqueous hydrogen azide [2], A DTA study showed a lesser thermal stability than lead azide [3], It is strongly endothermic (AH°f (s) +451 kJ/mol, 2.32 kJ/g). 

Use of nitrous acid to liberate a free keto-acid from its semicarbazone caused formation of hydrogen azide which was co-extracted into ether with the product. Addition of silver nitrate to precipitate the silver salt of the acid also precipitated silver azide, which later exploded on scraping from a sintered disc. The possibility of formation of free hydrogen azide from interaction of nitrous acid and hydrazine or hydroxylamine derivatives is stressed. 

Rice, F. O. et al., J. Amer. Chem. Soc., 1957, 79, 1880-1881 This blue solid (a cyclic dimer of diazene, 93.3% of nitrogen), obtained by freezing out at — 195°C the pyrolysis products of hydrogen azide, is extremely explosive above this temperature. An explosion at — 125°C destroyed the apparatus. 

An explosion was experienced dining work up of an epoxide opening reaction involving acidified sodium azide in a dichloromethane/dimethyl sulfoxide solvent. The author ascribes this to diazidomethane formation from dichloromethane [1]. A second report of an analoguous accident, also attributed to diazidomethane, almost certainly involved hydrogen azide for the cold traps of a vacuum pump on a rotary evaporator were involved this implies an explosive more volatile than dichloromethane. It is recommended that halogenated solvents be not used for azide reactions [2]. 

Ross, F. F., Water Waste Treatment, 1964, 9, 528 private comm., 1966 One of the reagents required for the determination of dissolved oxygen in polluted water is a solution of sodium azide in 50% sulfuric acid. It is important that the diluted acid should be quite cold before adding the azide, since hydrogen azide boils at 36°C and is explosive in the condensed liquid state. 

An explosion occurred during blending and screening operations on a mixture of lead azide and 0.5% of calcium stearate. If free stearic acid were present as impurity in the calcium salt, free hydrogen azide may have been involved. 

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