Sodium azide

Colorless powder

Fixed

1.85 g · cm -3 ( 20 ° C)

275 ° C ( decomposition)

Good in water ( 420 g · l-1 at 20 ° C) and liquid ammonia, and insoluble in diethyl ether

Risk

0.2 mg · m-3

27 mg · kg -1 ( LD50, rat, oral)

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Sodium is the sodium salt of hydrazoic acid. It has the formula NaN3 and belongs to the class of the azides.

Representation

Sodium azide is formed when passing through nitrous sodium at 180 ° C:

As a by- product is produced according to the following equation ammonia:

The end of the reaction can be determined by the lack of development of ammonia gas.

Also obtained from sodium amide and sodium azide, sodium nitrate in the melt at 175 ° C. Byproducts of sodium hydroxide and ammonia.

Description / Features

In acidic solution is formed from sodium azide explosive hydrazoic acid HN3. When heated it decomposes above a temperature of 275 ° C.

The azide can, however, melt without decomposition and fizzles only when stronger heating or strong shock.

The azide ion N3 - is one of the pseudohalides. It behaves similarly to the halide ions in many reactions. The ion resonance-stabilized linear and symmetric constructed with uniform distances between the nitrogen atoms. Their bond length between the NN double and triple bonds. This stabilization is missing in the free acid and in the Schwermetallaziden.

Application

Sodium azide is used in the industrial synthesis for the preparation of lead azide and hydrazoic acid and tert- alkyl azides and other organic azides such as tosyl azide ( Hunnius, Rompp, Willmes ) is used.

The reaction of carbonyl compounds with hydrazoic acid in strongly acidic medium yields from ketones in the migration of an alkyl amides. If carboxylic acids are used, one obtains the poorer by one carbon atom amine ( Schmidt reaction ). The hydrazoic acid needed for this is generated in situ from sodium azide. A further application is the preparation of alkyl isocyanates from carboxylic acid halides (Curtius reaction).

Furthermore, the sodium azide and 1995 used in fuels for air bags to fill the airbag.

Analysis

Analysis is made of the property of the azides advantage to react with iodine only in the presence of thiols or thiol compounds potential ( such as penicillin ) ( iodine -azide reaction). This reaction is very sensitive; it creates nitrogen and hydrogen iodide. For the detection of iodine solution and aqueous sodium azide are added together. Then the sample solution ( mercaptans, thioethers, disulfides, thiones, S- heterocyclic compounds ) is added. After a short time, the solution decolorized with evolution of gas. The result is a nitrogen according to the following equation:

Biological effect

Versatility is sodium in all areas where the growth of micro-organisms to be prevented. So can be kept longer aseptically in laboratories with sodium azide use materials ( beakers, etc.). The chemical is also solutions, dispersions etc., are added (about 0.1 to 0.001 %), which are very susceptible to microbial spoilage by virtue of their composition (for example solutions of biopolymers protein dispersions).

The biochemical mechanism of action is the disruption of the electron transport chain of the respiratory chain. The azide ion blocks - as cyanide and carbon monoxide, - the oxygen binding site in the active site of the cytochrome c oxidase irreversible. This ATP production comes to a halt and the cell dies. The cytochrome c oxidase is found in the most oxygen- breathing organisms, therefore azide is a fairly universal poison - also for mammals.

Safety

From acidic Natriumazidlösungen hydrazoic acid is released. This is highly toxic and corrosive to the mucous membranes. Anhydrous hydrazoic acid explode when heated and with low vibration. Concentrated solutions may not heat or splashing transferred or set down hard with the vessel. Sodium azide inhibits specific enzymes that contain heavy metals and therefore has toxic. The azide ion also has a profound hypotensive effect. Even the inhalation or ingestion of small amounts ( eg, 1.5 ml of 10 % solution ) has strong symptoms of poisoning result. Hydrazoic acid and its solutions unbearable smell pungent and evoke at exposure dizziness, headache and skin irritation.