Azides

from Wikipedia, the free encyclopedia

As azides is referred to the salts and organic compounds of hydrazoic acid . They belong to the pseudohalides . Many azides are very toxic. The soluble salts irreversibly inhibit the enzyme cytochrome C oxidase in the respiratory chain in cells .

Heavy metal azides are highly explosive, the azides of the alkali and alkaline earth metals, however, only fizzle out when exposed to strong heat after they have already melted.

The most important ionic azides are sodium azide and lead azide .

Inorganic azides

Sodium azide

Sodium azide is a colorless compound that is soluble in water. The sodium azide is very diluted and used as a preservative , for example in the processing of perishable substances such as insulin , and as a starting material for the production of other azides and the free hydrazoic acid. It is also used in the iodine-azide reaction to detect divalent sulfur in sulfides and thioethers . It is also used in airbags to fill the sack. The decomposition can be triggered by heating or an electrical impulse (with airbags) and proceeds according to the following stoichiometric equation:

Lead azide

Lead azide is insoluble in cold water and is resistant to heat and moisture. When slowly cooling down from hot, aqueous solutions, long crystals are formed that detonate when they break under water. Therefore, in industrial production, the formation of larger crystals is strictly avoided by adding a little dextrin and stirring. Its detonation point is 350 ° C. It is made by precipitating sodium azide with a water-soluble lead salt compound such as lead acetate . Lead azide is used as a primer , mixed with lead trinitroresorcinate . The latter serves to increase the spark sensitivity, since the detonation point of the azide is high.

Silver azide

In contrast to lead azide, silver azide is significantly more unstable when exposed to light and, in analogy to classical photography using silver halides, quickly turns deep purple. It is more suitable than lead azide for demonstration experiments, as it is completely insoluble even in hot water and always separates out in the finest crystals. The impact sensitivity is not greater than that of lead azide. Due to the high price, however, the possible application as a technically used primer is very limited.

Copper azide

Copper azide is extremely explosive and often explodes when touched. It is therefore not used for technical purposes and is also unsuitable as an initiator.

General formula of three mesomeric boundary structures of an organic azide with the functional group of the azide marked blue . R is an organyl radical ( alkyl radical, aryl radical, alkylaryl radical, acyl radical, etc.).

Silicon tetraazide

Silicon tetraazide is a thermally unstable, covalent silicon - nitrogen compound with a nitrogen content of 85.7%. The high-energy, crystalline substance tends to spontaneously and explosively decompose from 0 ° C. Further coordination to the six-coordinate structure as in hexaazidosilicates [Si (N 3 ) 6 ] 2− or in adducts with divalent ligands Si (N 3 ) 4 L 2 leads to relatively stable, crystalline solids that can be handled normally at room temperature.

Organic azides

There are many organic compounds with an azido group (-N 3 ), hence they are referred to as organic azides. Methyl azide is the simplest representative of the organic azides. The four times substituted methane derivative tetraazidomethane is a thermally unstable liquid with a nitrogen content of 93.3%. The high-energy substance, which tends to spontaneously decompose explosively, was first produced in 2006. The drug azidothymidine (AZT) is known.

Carboxylic acid azides [R-CO-N 3 ] are used in the Curtius rearrangement , in which they are rearranged to isocyanates. Another important reaction of the azides is the 1,3-dipolar cycloaddition ( Huisgen reaction ). Known since the 1960s, it has become increasingly important as a so-called bioorthogonal reaction in the last decade. The reduction of alkyl azides (e.g. with lithium aluminum hydride ) yields primary amines; the route via azides is an alternative to the Gabriel synthesis .

literature

Individual evidence

  1. ↑ E. Wilberg, H. Michaud: On the knowledge of a silicon terazide Si (N 3 ) 4 . In: Journal of Nature Research B . 9, 1954, p. 500 ( online ).
  2. ^ AC Filippou , P. Portius, G. Schnakenburg: The Hexaazidosilicate (IV) Ion: Synthesis, Properties, and Molecular Structure. In: J. Am. Chem. Soc. 124, 2002, pp. 12396-12397, doi : 10.1021 / ja0273187 .
  3. ↑ P. Portius, AC Filippou, G. Schnakenburg, M. Davis, K.-D. Wehrstedt: Neutral Lewis base adducts of silicon tetraazide. In: Angew. Chem. 122, 2010, pp. 8185-8189, doi : 10.1002 / anie.201001826 .
  4. ↑ K. Banert, Y.-H. Joo, T. Rüffer, B. Walfort, H. Lang: The exciting chemistry of tetraazidomethane. In: Angew. Chem. 119, 2007, pp. 1187-1190, doi : 10.1002 / anie.200603960 .
  5. ^ R. Huisgen, R. Grashey, J. Sauer: In: Chemistry of Alkenes , Interscience, New York, 1964, pp. 806-877.
  6. ↑ D. Amantini, F. Fringuelli, O. Piermatti, F. Pizzo, E. Zunino, L. Vaccaro: In: J. Org. Chem. 70, 2005, pp. 6526-6529.
  7. ^ VV Rostovtsev, LG Green, VV Fokin, KB Sharpless: In: Angew. Chem. 114, 2002, pp. 2708-2711.