Sodium azide (NaN3) structure, properties, uses, risks

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Robert Johnston
Sodium azide (NaN3) structure, properties, uses, risks

The Sodium azide is a crystalline inorganic solid formed by the sodium ion Na+ and the azide ion N3-. Its chemical formula is NaN3. The compound NaN3 is the sodium salt of hydrazoic acid HN3. The NaN3 is a colorless to white crystalline solid.

Although it is a very toxic compound, one of its most widespread uses has been in air bags that inflate instantly during vehicle accidents. It is also used to quickly inflate emergency slides on airplanes. However, its use is currently being highly questioned in both cases due to its toxicity..

NaN sodium azide3 solid. И.С. Непоклонов [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]. Source: Wikimedia Commons.

It is used in chemical research laboratories to synthesize various types of compounds and in biochemical laboratories for studies with bacteria, fungi, or mammalian or human cells.

In some laboratories it is used to sterilize materials or equipment, but certain types of microorganisms resist its biocidal action.

It has also been used in agriculture to eliminate parasites from the soil or in the lumber industry to prevent pine wood from staining with fungi.

Article index

  • 1 Structure
  • 2 Nomenclature
  • 3 Properties
    • 3.1 Physical state
    • 3.2 Molecular weight
    • 3.3 Melting point
    • 3.4 Density
    • 3.5 Solubility
    • 3.6 Dissociation constants
    • 3.7 Chemical properties
    • 3.8 Biochemical properties
  • 4 Obtaining
  • 5 Uses
    • 5.1 In motor vehicles and aircraft
    • 5.2 In the chemical industry
    • 5.3 In agriculture
    • 5.4 In the preparation of other chemical compounds
    • 5.5 In the explosives industry
    • 5.6 In biochemical laboratories
    • 5.7 In various uses
  • 6 Risks
  • 7 References

Structure

NaN sodium azide3 is formed by a sodium cation Na+ and an azide anion N3-.

Sodium azide is made up of the sodium ion Na+ and the azide ion N3-. Lukáš Mižoch [Public domain]. Source: Wikimedia Commons.

The azide ion N3- It is made up of 3 nitrogen atoms (N) joined together by covalent bonds that can be single, double or triple, since the electrons are shared between the three.

Said anion has a linear structure, that is, the three nitrogen atoms arranged in a straight line. In addition, the structure is symmetrical.

Possible Lewis structures of the azide anion. Author: Marilú Stea.

Nomenclature

- Sodium azide

- Sodium azide

Properties

Physical state

Colorless to white crystalline solid. Hexagonal crystals.

Molecular weight

65.01 g / mol

Melting point

It decomposes at 275 ºC.

Density

1.846 g / cm3 at 20 ºC

Solubility

It is very soluble in water: 41.7 g / 100 mL at 17 ºC. It is slightly soluble in ethanol and insoluble in ethyl ether.

Dissociation constants

Has a pKb of 9.3. Aqueous solutions contain NH3, which quickly escapes to the environment at 37 ºC.

Chemical properties

The NaN3 it is very corrosive towards aluminum and moderately towards copper and lead.

According to a certain source, sodium azide is not explosive. It decomposes smoothly and completely when heated to 300 ° C or more, forming sodium metal Na and nitrogen gas Ntwo.

2 NaN3 → 2 Na + 3 Ntwo

It is a nitriding agent, this means that it serves to nitrogenize or add nitrogen to other chemical compounds or to the surface of materials such as steel..

It is stable in neutral or alkaline water in the absence of light. It is decomposed by solar radiation.

Biochemical properties

Sodium azide inhibits an enzyme called cytochrome oxidase which is found in the mitochondria of cells and is significantly involved in respiration and energy generation in this.

Its action prevents the generation of ATP, a key compound in cellular activities and the cell deteriorates or damages.

If ingested, inhaled or in contact with sodium azide, it is very toxic and can be fatal..

Obtaining

Ammonia NH is reacted3 with sodium metal Na at 350 ºC in a closed steel container, obtaining sodium amide NaNHtwo.

Sodium amide NaNHtwo is reacted with dinitrogen monoxide NtwoOr at 230 ºC in a nickel reactor, and thus a mixture of sodium azide NaN is formed3, sodium hydroxide NaOH and ammonia NH3.

2 NaNHtwo + NtwoO → NaN3 + NaOH + NH3

It can also be obtained by reacting sodium amide with sodium nitrate NaNO3 at 175 ºC:

3 NaNHtwo + Elder brother3 → NaN3 + 3 NaOH + NH3

To purify the azide, water is added to the mixture, the azide crystals are washed, and then the water is evaporated. The remaining crystalline material is sodium azide NaN3 which is then dried at 110 ºC.

Applications

In motor vehicles and aircraft

Sodium azide has been widely used in the automotive industry as a nitrogen generator to rapidly inflate air bags. airbags) safety of the steering wheels of cars and trucks when an impact occurs.

It has also been used in inflatable slides that serve to quickly escape from the interior of planes that have landed in emergency situations..

In both cases, the mechanism involves the action of a spark to produce an immediate reaction between sodium azide and certain compounds, generating nitrogen gas Ntwo and sodium oxide NatwoOR.

In this application, the instantaneous release of a cold and non-toxic gas is required, so nitrogen is the most appropriate gas..

Security bags that have already been used in vehicles. Author: Marcel Langthim. Source: Pixabay.

However, this use is decreasing due to the toxicity of sodium azide and less toxic compounds are being used instead..

In the chemical industry

It is used as a retarder in the manufacture of sponge rubber, to prevent the coagulation of styrene or butadiene latex when they are stored in contact with metals and to decompose nitrites in the presence of nitrates.

In agriculture

It has been used in agriculture: as a biocide and fumigant, it is also a nematicide, that is, it is applied to soils to eliminate nematodes, which are parasites that attack some crops.

Damage caused by nematodes in the root of a plant. Author: RedWolf. [http://www.ars-grin.gov/ars/SoAtlantic/fp/stpp/burelle/burelle.html] Source: Wikimedia Commons.

It has also worked as a herbicide and to prevent fruit rot.

Recently the NaN3 has been used in the preparation of okra or okra seeds to observe their resistance to waterlogging conditions.

Seeds to which NaN was previously applied3 generated seedlings that withstood the flood conditions better than the untreated ones, improved the height of the plants, increased the number of leaves and increased the number of roots even with excess water.

In the preparation of other chemical compounds

It is used as a chemical reagent in the synthesis of organic compounds, for example to prepare many organic azides, such as tosyl azide or azides of tertiary alkyl groups, which are important in chemical synthesis.

It is used to prepare hydrazoic acid (HN3) and pure sodium (Na).

In the explosives industry

NaN sodium azide3 is an intermediate in the manufacture of explosives, as it is used for the preparation of lead azide Pb (N3)two. The latter is a compound that explodes when struck with force, which is why it is used in the construction of detonating devices..

NaN sodium azide3 is used to make lead azide Pb (N3)two compound that is part of devices to generate explosions. Author: OpenClipart-Vectors. Source: Pixabay.

In biochemical laboratories

Sodium azide is used when sterile laboratory equipment is required, as it is capable of destroying different types of microorganisms.

It is a biocidal agent. However, some sources indicate that some types of bacteria are resistant to its action..

This is achieved by blocking the oxygen binding site in cytochrome oxidase, which is an enzyme involved in the energy production process of some microorganisms..

It is used in automatic blood counters, also in the differential selection of bacteria and to preserve laboratory reagent solutions as it prevents the growth of certain microorganisms in these.

In various uses

Sodium azide is used in the lumber industry to prevent the growth of brown fungal spots on pine wood..

It has also been used in the Japanese beer industry to prevent the development of a fungus that darkens the beer..

Risks

Sodium azide is a toxic compound that inhibits an enzyme important for respiration and the life of human and animal cells. It has been found that it can severely affect the cells of the blood vessel tissue of the brain.

Its immediate effect after ingestion, inhalation or skin contact is to dangerously lower blood pressure, which can lead to death. Therefore, it must be handled with great caution..

There are sources of information that call attention to the air bags of vehicles that are destroyed in waste areas.

In such cases, people who are unaware of the danger could access the NaN deposits.3, this being a very toxic compound. In addition, there is a danger of contamination with NaN3 soil and water.

Likewise, during accidents, collisions or vehicle fires, people could be exposed to NaN3 and this may be underestimated or unknown by the medical personnel attending the emergency.

Attention has also been drawn to the exposure of laboratory personnel using it..

References

  1. Vwioko, E.D. et al. (2019). Sodium Azide Priming Enhances Waterlogging Stress Tolerance in Okra (Abelmoschus esculentus). Agronomy 2019, 9, 670. Recovered from mdpi.com.
  2. Kho, D.T. et al. (2017). Death of Blood Brain Barrier Endothelial Cells to Sodium Azide and Its Gaseous Products. Biosensors 2017, 7, 41. Recovered from mdpi.com.
  3. U.S. National Library of Medicine. (2019). Sodium azide. Recovered from: pubchem.ncbi.nlm.nih.gov.
  4. Talavera, M. et al. (2019). Nematode Management in the Strawberry Fields of Southern Spain. Agronomy 2019, 9, 252. Recovered from mdpi.com.
  5. Okano, T. et al. (nineteen ninety five). Mechanism of cell detachment from temperature-modulated, hydrophilic-hydrophobic polymer surfaces. In The Biomaterials: Silver Jubilee Compendium. Recovered from sciencedirect.com.
  6. Ullmann's Encyclopedia of Industrial Chemistry. (1990). Fifth Edition. Volume A22. VCH Verlagsgesellschaft mbH.
  7. Cotton, F. Albert and Wilkinson, Geoffrey. (1980). Advanced Inorganic Chemistry. Fourth Edition. John Wiley & Sons.
  8. Chang, S. and Lamm, S.H. (2003). Human Health Effects of Sodium Azide Exposure: A Literature Review and Analysis. Int J Toxicol 2003, 22 (3): 175-86. Recovered from ncbi.nlm.nih.gov.

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