Sodium Azide
Properties
| State | Solid (white crystalline powder; odorless) |
| Color | White |
| Solubility | Soluble in water (417 g/L at 17 °C); slightly soluble in ethanol |
| Melting Point | 275 °C (decomposes explosively) |
| Boiling Point | Decomposes before boiling |
About Sodium Azide
Sodium azide is the workhorse source of the linear, symmetric N3- anion — isoelectronic with CO2 and one of the most synthetically useful nucleophiles in the SN2 chemist's toolkit. Molar mass 65.01 g/mol, decomposes around 275 °C with a thermodynamic itch to release nitrogen gas: 2 NaN3 → 2 Na + 3 N2. That single decomposition reaction was the basis of the first-generation automotive airbag — a pellet of NaN3 plus oxidizers (KNO3, SiO2) and a squib gave roughly 50–80 g of NaN3 enough N2 to fill a 60-liter driver bag in 30–50 ms. Modern airbags have largely moved to guanidine nitrate or ammonium nitrate inflators because metallic sodium byproducts and azide handling at end-of-life are nasty. In organic synthesis, NaN3 in DMF or DMSO converts alkyl halides to alkyl azides, which then become amines via Staudinger reduction or LiAlH4, or feed into copper-catalyzed click chemistry (CuAAC) to make 1,4-disubstituted triazoles. In biochem, 0.02-0.05 percent NaN3 is the standard preservative in column buffers and antibody stocks because it irreversibly inhibits cytochrome c oxidase and shuts down bacterial respiration.
Where you'll encounter it
If you've ever pipetted from a bottle of antibody at 0.02 percent NaN3 in PBS, you've handled the same chemistry that inflated millions of car airbags — just at a billion-fold lower concentration. The most common lab accident with azide is not poisoning but explosion: pour an aqueous azide waste stream down a copper or lead drain trap and over months you build up shock-sensitive Cu(N3)2 or Pb(N3)2 crystals that detonate when a plumber finally reaches in with a wrench. There are documented hospital cases. In click chemistry — now Nobel-winning bioconjugation work — NaN3 is the source of the azide partner that snaps onto a terminal alkyne with copper catalysis to label proteins, sugars, and even live cells. Forensic toxicology occasionally sees azide poisonings from contaminated mock-laboratory drink spikings; the antidote is essentially supportive care because no specific binder exists.
Common Uses
- Inflator chemistry in first-generation automotive airbag modules
- 0.02–0.05% bacteriostatic preservative in antibody and protein buffer stocks
- Nucleophilic azidation of primary alkyl halides in SN2 synthesis
- Azide partner in copper-catalyzed alkyne-azide click cycloadditions
- Mechanistic probe blocking cytochrome c oxidase in mitochondrial research
- Lead azide and silver azide synthesis precursor for primary detonators
- Tetrazole ring construction from nitriles via [3+2] cycloaddition
Safety Information
Acutely toxic and a serious explosion hazard. GHS: H300 (fatal if swallowed), H310 (fatal in skin contact), H373 (chronic organ damage), H410 (very toxic to aquatic life). Oral LD50 in rats is 27 mg/kg — comparable to potassium cyanide. OSHA PEL ceiling is 0.1 mg/m³ as NaN3 (0.3 mg/m³ as HN3 vapor) for an 8-hour TWA. Reaction with any acid liberates volatile, highly toxic, shock-sensitive hydrazoic acid (HN3, BP 37 °C). Reaction with copper, lead, silver, or mercury plumbing or apparatus forms primary explosive metal azides that detonate spontaneously when dry. Destroy azide waste with ceric ammonium nitrate or NaNO2/H2SO4 before drain disposal. Use stainless steel only. Work in a fume hood with nitrile double-gloves and a face shield.
This safety summary is for educational reference only and may not be complete. It is not a substitute for Safety Data Sheets (SDS), medical advice, or professional chemical safety guidance. Always consult appropriate SDS and qualified professionals before handling chemicals.