| IUPAC name
| Other names
|Molar mass||33.03 g/mol|
|Appearance||White hygroscopic crystals|
|Density||1.227 g /cm3 (at 20 °C)|
|Melting point||33 °C (91 °F; 306 K)|
|Boiling point||70 °C (158 °F; 343 K) (at 60 mm Hg; decomposes)|
|Solubility|| Soluble in liq. ammonia, ethanol, methanol|
Poorly soluble in diethyl ether, carbon disulfide, chloroform, propanol,
Insoluble in acetone, benzene, petroleum ether, hydrogen sulfide
|Vapor pressure||53 mm Hg at 32 °C|
Std enthalpy of
|Flash point||Explodes at 129 °C|
|Lethal dose or concentration (LD, LC):|
LD50 (Median dose)
| 408 mg/kg (oral, mouse)|
9–70 mg/kg (intraperitoneal mouse, rat); 29 mg/kg (subcutaneous, rat)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Hydroxylamine is a white crystalline solid, widely used as a reducing agent. It has the chemical formula NH2OH.
As pure hydroxylamine is unstable and explosive, its salts such as hydroxylammonium chloride are more often used. It can also be encountered as aqueous solution.
Hydroxylamine reacts with acids to give hydroxylammonium salts.
- 2 NH2OH + 4 CuO → 2 Cu2O + N2O + 3 H2O
Hydroxylamine is a white crystalline solid, hygroscopic and unstable when pure. It is very soluble in water and alcohol.
Freebase hydroxylamine can explode if heated.
Pure hydroxylamine is not sold by any entity. However, aqueous solutions are sold by many chemical entities, though they're not readily accessible to the amateur chemist.
Hydroxylammonium salts are also available.
Hydroxylamine can be prepared through various means:
The Raschig process is the most common route. It involves the reduction of ammonium nitrite with bisulfite (HSO3−) and sulfur dioxide at 0 °C in water to hydroxylamido-N,N-disulfonate anion, which hydrolyzes to give hydroxylamine sulfate.
- NH4NO2 + 2 SO2 + NH3 + H2O → 2 NH4+ + N(OH)(OSO2)22-
- N(OH)(OSO2)22− + H2O → NH(OH)(OSO2)- + HSO4-
- 2 NH(OH)(OSO2)− + 2 H2O → (NH3OH)2SO4 + SO42-
To obtain pure hydroxylamine, anhydrous ammonia is added:
- (NH3OH)2SO4 + 2 NH3 → 2 NH2OH +(NH4)2SO4
Since free hydroxylamine quickly breaks down, the final product is either dissolved in water or reacted with a strong acid, like hydrochloric acid.
Electrolytic reduction of nitric acid with sulfuric acid at 15-20 °C for 40 minutes at 24 A gives hydroxylamine:
- HNO3 + 3 H2 → NH2OH + 2 H2O
Other acids, such as hydrochloric and phosphoric acids can also be used. The yield of this route is between 50-80%.
- CH3NO2 + HCl → NH2OH·HCl + 2 H2O + CO
- Make oximes
- Make hydroxylammonium nitrate
- Purify ketones and aldehydes
- Make nitrous oxide
- Caprolactam synthesis
- Make Nylon 6
- Make formaldoxime
Hydroxylamine is an irritant to the respiratory tract, skin, eyes, and other mucous membranes. It is harmful if swallowed and may be absorbed through the skin. Hydroxylamine is considered a possible mutagen.
Hydroxylamine explodes upon heating, though the exact mechanism is not well understood. Ferrous and ferric salts accelerate its decomposition in aqueous solution.
Hydroxylamine is safe to store only as aqueous solution or in salt form.
Hydroxylamine can be neutralized by adding a ketone and then gently heating the resulting oxime, which reforms the ketone and releases nitrogen gas and water. It can also be neutralized by diluting it with water and carefully adding iron salts or other compounds that accelerate its decomposition.
- Schoch, E. P.; Pritchett, R. H.; Journal of the American Chemical Society; vol. 38; (1916); p. 2042
- Tafel, J.; Z. Anorg. Chem.; vol. 31; (1902); p. 321 - 324
- Raschig, F.; Z. Anorg. Chem.; vol. 155; (1926); p. 225