Sodium azide

Last updated
Sodium azide
Sodium azide.svg
NaN3SmallSection.tif
Sodium azide 01.JPG
Names
IUPAC name
Sodium azide
Other names
Sodium trinitride
Smite
Azium
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.043.487 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 247-852-1
PubChem CID
RTECS number
  • VY8050000
UNII
UN number 1687
  • InChI=1S/N3.Na/c1-3-2;/q-1;+1 Yes check.svgY
    Key: PXIPVTKHYLBLMZ-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/N3.Na/c1-3-2;/q-1;+1
    Key: PXIPVTKHYLBLMZ-UHFFFAOYAH
  • [N-]=[N+]=[N-].[Na+]
Properties
NaN3
Molar mass 65.0099 g/mol
AppearanceColorless to white solid
Odor Odorless
Density 1.846 g/cm3 (20 °C)
Melting point 275 °C (527 °F; 548 K) violent decomposition
38.9 g/100mL (0 °C)
40.8 g/100mL (20 °C)
55.3 g/100mL (100 °C)
Solubility Very soluble in ammonia
Slightly soluble in benzene
Insoluble in diethyl ether, acetone, hexane, chloroform
Solubility in methanol 2.48 g/100mL (25 °C)
Solubility in ethanol 0.22 g/100mL (0 °C)
Acidity (pKa)4.8
Structure
Hexagonal, hR12 [1]
R-3m, No. 166
Thermochemistry
76.6 J/mol·K
Std molar
entropy
(S298)
70.5 J/mol·K
21.3 kJ/mol
99.4 kJ/mol
Hazards
GHS labelling:
GHS-pictogram-explos.svg GHS-pictogram-skull.svg GHS-pictogram-silhouette.svg GHS-pictogram-pollu.svg
Danger
H300, H310, H410
P260, P280, P301+P310, P501 [2]
NFPA 704 (fire diamond)
NFPA 704.svgHealth 4: Very short exposure could cause death or major residual injury. E.g. VX gasFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 3: Capable of detonation or explosive decomposition but requires a strong initiating source, must be heated under confinement before initiation, reacts explosively with water, or will detonate if severely shocked. E.g. hydrogen peroxideSpecial hazards (white): no code
4
1
3
Flash point 300 °C (572 °F; 573 K)
Lethal dose or concentration (LD, LC):
27 mg/kg (oral, rats/mice) [1]
NIOSH (US health exposure limits):
PEL (Permissible)
None [3]
REL (Recommended)
C 0.1 ppm (as HN3) [skin]
C 0.3 mg/m3 (as NaN3) [skin] [3]
IDLH (Immediate danger)
N.D. [3]
Safety data sheet (SDS) ICSC 0950
Related compounds
Other anions
Sodium cyanide
Other cations
Potassium azide
Ammonium azide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Sodium azide is an inorganic compound with the formula NaN3. This colorless salt is the gas-forming component in some car airbag systems. It is used for the preparation of other azide compounds. It is an ionic substance, is highly soluble in water, and is acutely poisonous. [5]

Contents

Structure

Sodium azide is an ionic solid. Two crystalline forms are known, rhombohedral and hexagonal. [1] [6] Both adopt layered structures. The azide anion is very similar in each form, being centrosymmetric with N–N distances of 1.18 Å. The Na+ ion has an octahedral geometry. Each azide is linked to six Na+ centers, with three Na–N bonds to each terminal nitrogen center. [7]

Preparation

The common synthesis method is the "Wislicenus process", which proceeds in two steps in liquid ammonia. In the first step, ammonia is converted to sodium amide by metallic sodium:

2 Na + 2 NH3 → 2 NaNH2 + H2

It is a redox reaction in which metallic sodium gives an electron to a proton of ammonia which is reduced in hydrogen gas. Sodium easily dissolves in liquid ammonia to produce solvated electrons responsible for the blue color of the resulting liquid. The Na+ and NH2 ions are produced by this reaction.

The sodium amide is subsequently combined with nitrous oxide:

2 NaNH2 + N2O → NaN3 + NaOH + NH3

These reactions are the basis of the industrial route, which produced about 250 tons per year in 2004, with production increasing due to the increased use of airbags. [5]

Laboratory methods

Curtius and Thiele developed another production process, where a nitrite ester is converted to sodium azide using hydrazine. This method is suited for laboratory preparation of sodium azide:

2 NaNO2 + 2 C2H5OH + H2SO4 → 2 C2H5ONO + Na2SO4 + 2 H2O
C2H5ONO + N2H4·H2O + NaOH → NaN3 + C2H5OH + 3 H2O

Alternatively the salt can be obtained by the reaction of sodium nitrate with sodium amide. [8]

Chemical reactions

Acid formation of hydrazoic acid

Treatment of sodium azide with strong acids gives gaseous hydrazoic acid (hydrogen azide; HN3), which is also extremely toxic:

H+ + N3 → HN3

Hydrazoic acid equilibrium

Aqueous solutions contain minute amounts of hydrazoic acid, the formation of which is described by the following equilibrium:

N3 + H2O ⇌ HN3 + OH, K = 10−4.6

Destruction

Sodium azide can be destroyed by treatment with in situ prepared nitrous acid (HNO2; not HNO3). [9] [10] In situ preparation is necessary as HNO2 is unstable and decomposes rapidly in aqueous solutions. This destruction must be done with great caution and within a chemical fume hood as the formed gaseous nitric oxide (NO) is also toxic, and an incorrect order of acid addition for in situ formation of HNO2 will instead produce gaseous highly toxic hydrazoic acid (HN3). [9]

2 NaN3 + 2 HNO2 → 3 N2 + 2 NO + 2 NaOH

Applications

Automobile airbags and aircraft evacuation slides

Older airbag formulations contained mixtures of oxidizers, sodium azide and other agents including ignitors and accelerants. An electronic controller detonates this mixture during an automobile crash:

2 NaN3 → 2 Na + 3 N2

The same reaction occurs upon heating the salt to approximately 300 °C. The sodium that is formed is a potential hazard alone and, in automobile airbags, it is converted by reaction with other ingredients, such as potassium nitrate and silica. In the latter case, innocuous sodium silicates are generated. [11] While sodium azide is still used in evacuation slides on modern aircraft, newer-generation automotive air bags contain less sensitive explosives such as nitroguanidine or guanidine nitrate. [12]

Organic and inorganic synthesis

Due to its explosion hazard, sodium azide is of only limited value in industrial-scale organic synthesis. In the laboratory, it is used to introduce the azide functional group by displacement of halides. [10] The azide functional group can thereafter be converted to an amine by reduction with either SnCl2 in ethanol or lithium aluminium hydride or a tertiary phosphine, such as triphenylphosphine in the Staudinger reaction, with Raney nickel or with hydrogen sulfide in pyridine. Oseltamivir, an antiviral medication, is currently produced in commercial scale by a method which utilizes sodium azide. [13]

Sodium azide is a versatile precursor to other inorganic azide compounds, e.g., lead azide and silver azide, which are used in detonators as primary explosives. These azides are significantly more sensitive to premature detonation than sodium azide and thus have limited applications. Lead and silver azide can be made via double displacement reaction with sodium azide and their respective nitrate (most commonly) or acetate salts. Sodium azide can also react with the chloride salts of certain alkaline earth metals in aqueous solution, such as barium chloride or strontium chloride to respectively produce barium azide and strontium azide, which are also relatively sensitive primarily explosive materials. These azides can be recovered from solution through careful desiccation.

Biochemistry and biomedical uses

Sodium azide is a useful probe reagent, and an antibacterial preservative for biochemical solutions. In the past merthiolate and chlorobutanol were also used as an alternative to azide for preservation of biochemical solutions. [14]

Sodium azide is an instantaneous inhibitor of lactoperoxidase, which can be useful to stop lactroperoxidase catalyzed 125I protein radiolabeling experiments. [15]

In hospitals and laboratories, it is a biocide; it is especially important in bulk reagents and stock solutions which may otherwise support bacterial growth where the sodium azide acts as a bacteriostatic by inhibiting cytochrome oxidase in gram-negative bacteria; however, some gram-positive bacteria (streptococci, pneumococci, lactobacilli) are intrinsically resistant. [16]

Agricultural uses

It is used in agriculture for pest control of soil-borne pathogens such as Meloidogyne incognita or Helicotylenchus dihystera . [17]

It is also used as a mutagen for crop selection of plants such as rice, [18] barley [19] or oats. [20]

Safety considerations

Sodium azide can be fatally toxic, [21] and even minute amounts can cause symptoms. The toxicity of this compound is comparable to that of soluble alkali cyanides, [22] although no toxicity has been reported from spent airbags. [23]

It produces extrapyramidal symptoms with necrosis of the cerebral cortex, cerebellum, and basal ganglia. Toxicity may also include hypotension, [24] blindness and hepatic necrosis. Sodium azide increases cyclic GMP levels in the brain and liver by activation of guanylate cyclase. [25]

Sodium azide solutions react with metallic ions to precipitate metal azides, which can be shock sensitive and explosive. This should be considered for choosing a non-metallic transport container for sodium azide solutions in the laboratory. This can also create potentially dangerous situations if azide solutions should be directly disposed down the drain into a sanitary sewer system. Metal in the plumbing system could react, forming highly sensitive metal azide crystals which could accumulate over years. Adequate precautions are necessary for the safe and environmentally responsible disposal of azide solution residues. [26]

Intentional consumption

Sodium azide has gained attention in the Netherlands [27] and abroad [28] as a chemical used for homicidal and suicidal purposes.

Sodium azide has been attributed to at least 172 deaths in the period from 2015 to 2022 as part of a illicit substance used as a suicide aid commonly called drug X (Dutch: middel X) [29] In 2021, a review of all case reports of sodium azide intoxication indicated that 37% of cases were suicide attempts. [30] An increase in the usage of sodium azide as a suicide drug has been attributed to its availability through online retailers. [31]

Related Research Articles

<span class="mw-page-title-main">Nitrogen</span> Chemical element, symbol N and atomic number 7

Nitrogen is a chemical element; it has symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at seventh in total abundance in the Milky Way and the Solar System. At standard temperature and pressure, two atoms of the element bond to form N2, a colorless and odorless diatomic gas. N2 forms about 78% of Earth's atmosphere, making it the most abundant uncombined element in air. Because of the volatility of nitrogen compounds, nitrogen is relatively rare in the solid parts of the Earth.

In chemistry, azide is a linear, polyatomic anion with the formula N−3 and structure N=N+=N. It is the conjugate base of hydrazoic acid HN3. Organic azides are organic compounds with the formula RN3, containing the azide functional group. The dominant application of azides is as a propellant in air bags.

<span class="mw-page-title-main">Nitrous acid</span> Chemical compound

Nitrous acid is a weak and monoprotic acid known only in solution, in the gas phase, and in the form of nitrite salts. It was discovered by Carl Wilhelm Scheele, who called it "phlogisticated acid of niter". Nitrous acid is used to make diazonium salts from amines. The resulting diazonium salts are reagents in azo coupling reactions to give azo dyes.

The nitrite ion has the chemical formula NO
2
. Nitrite is widely used throughout chemical and pharmaceutical industries. The nitrite anion is a pervasive intermediate in the nitrogen cycle in nature. The name nitrite also refers to organic compounds having the –ONO group, which are esters of nitrous acid.

<span class="mw-page-title-main">Sodium nitrite</span> Chemical compound

Sodium nitrite is an inorganic compound with the chemical formula NaNO2. It is a white to slightly yellowish crystalline powder that is very soluble in water and is hygroscopic. From an industrial perspective, it is the most important nitrite salt. It is a precursor to a variety of organic compounds, such as pharmaceuticals, dyes, and pesticides, but it is probably best known as a food additive used in processed meats and (in some countries) in fish products.

<span class="mw-page-title-main">Hydrazoic acid</span> Unstable and toxic chemical compound

Hydrazoic acid, also known as hydrogen azide, azic acid or azoimide, is a compound with the chemical formula HN3. It is a colorless, volatile, and explosive liquid at room temperature and pressure. It is a compound of nitrogen and hydrogen, and is therefore a pnictogen hydride. The oxidation state of the nitrogen atoms in hydrazoic acid is fractional and is -1/3. It was first isolated in 1890 by Theodor Curtius. The acid has few applications, but its conjugate base, the azide ion, is useful in specialized processes.

<span class="mw-page-title-main">Guanidine nitrate</span> Chemical compound

Guanidine nitrate is the chemical compound with the formula [C(NH2)3]NO3. It is a colorless, water-soluble salt. It is produced on a large scale and finds use as precursor for nitroguanidine, fuel in pyrotechnics and gas generators. Its correct name is guanidinium nitrate, but the colloquial term guanidine nitrate is widely used.

<span class="mw-page-title-main">Silver azide</span> Chemical compound

Silver azide is the chemical compound with the formula AgN3. It is a silver(I) salt of hydrazoic acid. It forms a colorless crystals. Like most azides, it is a primary explosive.

The chemical element nitrogen is one of the most abundant elements in the universe and can form many compounds. It can take several oxidation states; but the most common oxidation states are -3 and +3. Nitrogen can form nitride and nitrate ions. It also forms a part of nitric acid and nitrate salts. Nitrogen compounds also have an important role in organic chemistry, as nitrogen is part of proteins, amino acids and adenosine triphosphate.

<span class="mw-page-title-main">Trimethylsilyl azide</span> Chemical compound

Trimethylsilyl azide is the organosilicon compound with the formula (CH3)3SiN3. A colorless liquid, it is a reagent in organic chemistry, serving as the equivalent of hydrazoic acid.

<span class="mw-page-title-main">Potassium azide</span> Chemical compound

Potassium azide is the inorganic compound having the formula KN3. It is a white, water-soluble salt. It is used as a reagent in the laboratory.

<span class="mw-page-title-main">Lithium azide</span> Chemical compound

Lithium azide is the lithium salt of hydrazoic acid. It is an unstable and toxic compound that decomposes into lithium and nitrogen when heated.

<span class="mw-page-title-main">Beryllium azide</span> Chemical compound

Beryllium azide, Be(N3)2, is an inorganic compound. It is the beryllium analog of hydrazoic acid.

<span class="mw-page-title-main">Barium azide</span> Chemical compound

Barium azide is an inorganic azide with the formula Ba(N3)2. It is a barium salt of hydrazoic acid. Like most azides, it is explosive. It is less sensitive to mechanical shock than lead azide.

<span class="mw-page-title-main">Silicon tetraazide</span> Chemical compound

Silicon tetraazide is a thermally unstable binary compound of silicon and nitrogen with a nitrogen content of 85.7%. This high-energy compound combusts spontaneously and can only be studied in a solution. A further coordination to a six-fold coordinated structure such as a hexaazidosilicate ion [Si(N3)6]2− or as an adduct with bicationic ligands Si(N3)4·L2 will result in relatively stable, crystalline solids that can be handled at room temperature.

<span class="mw-page-title-main">Rubidium azide</span> Chemical compound

Rubidium azide is an inorganic compound with the formula RbN3. It is the rubidium salt of the hydrazoic acid HN3. Like most azides, it is explosive.

<span class="mw-page-title-main">Boron triazide</span> Chemical compound

Boron triazide, also known as triazidoborane, is a thermally unstable compound of boron and nitrogen with a nitrogen content of 92.1 %. Formally, it is the triazido derivative of borane and is a covalent inorganic azide. The high-energy compound, which has the propensity to undergo spontaneous explosive decomposition, was first described in 1954 by Egon Wiberg and Horst Michaud of the University of Munich.

An organic azide is an organic compound that contains an azide functional group. Because of the hazards associated with their use, few azides are used commercially although they exhibit interesting reactivity for researchers. Low molecular weight azides are considered especially hazardous and are avoided. In the research laboratory, azides are precursors to amines. They are also popular for their participation in the "click reaction" between an azide and an alkyne and in Staudinger ligation. These two reactions are generally quite reliable, lending themselves to combinatorial chemistry.

Cobalt compounds are chemical compounds formed by cobalt with other elements.

Homoleptic azido compounds are chemical compounds in which the only anion or ligand is the azide group, -N3. The breadth of homoleptic azide compounds spans nearly the entire periodic table. With rare exceptions azido compounds are highly shock sensitive and need to be handled with the upmost caution. Binary azide compounds can take on several different structures including discrete compounds, or one- two, and three-dimensional nets, leading some to dub them as "polyazides". Reactivity studies of azide compounds are relatively limited due to how sensitive they can be. The sensitivity of these compounds tends to be correlated with the amount of ionic or covalent character the azide-element bond has, with ionic character being far more stable than covalent character. Therefore, compounds such as silver or sodium azide – which have strong ionic character – tend to possess more synthetic utility than their covalent counterparts. A few other notable exceptions include polymeric networks which possess unique magnetic properties, group 13 azides which unlike most other azides decompose to nitride compounds (important materials for semiconductors), other limited uses as synthetic reagents for the transfer of azide groups, or for research into high-energy-density matter.

References

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