View source for Hydroxylamine

{{Chembox
| Name = Hydroxylamine
| Reference =
| IUPACName = Hydroxylamine
| PIN =
| SystematicName =
| OtherNames = Azinous acid<br>Aminol<br>Azanol<br>Hydroxyamine<br>Hydroxyazane<br>Hydroxylazane<br>Nitrinous acid
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| Section1 = {{Chembox Identifiers
| 3DMet = 
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  }}
| Section2 = {{Chembox Properties
| AtmosphericOHRateConstant = 
| Appearance = White hygroscopic crystals
| BoilingPt = 
| BoilingPtC = 70
| BoilingPt_ref = 
| BoilingPt_notes = (at 60 mm Hg; decomposes)
| Density = 1.227 g /cm<sup>3</sup> (at 20 °C)
| Formula = NH<sub>2</sub>OH
| HenryConstant = 
| LogP = −0.758
| MolarMass = 33.03 g/mol
| MeltingPt = 
| MeltingPtC = 33
| MeltingPt_ref = 
| MeltingPt_notes = 
| pKa = 5.95
| pKb = 8.05
| Solubility = Soluble
| SolubleOther = Soluble in liq. [[ammonia]], [[ethanol]], [[methanol]]<br>Poorly soluble in [[diethyl ether]], [[carbon disulfide]], [[chloroform]], [[propanol]], <br>Insoluble in [[acetone]], [[benzene]], [[petroleum ether]], [[hydrogen sulfide]]
| Solvent = 
| VaporPressure = 53 mm Hg at 32 °C
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| Section3 = {{Chembox Structure
| Coordination = 
| CrystalStruct = 
| MolShape = Tetrahedral at N
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| Section4 = {{Chembox Thermochemistry
| DeltaGf = 
| DeltaHc = 
| DeltaHf = −39.9 kJ·mol<sup>−1</sup>
| Entropy = 236.18 J·K<sup>−1</sup>·mol<sup>−1</sup>
| HeatCapacity = 46.47 J·K<sup>−1</sup>·mol<sup>−1</sup>
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| Section5 = {{Chembox Explosive
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| Section6 = {{Chembox Hazards
| AutoignitionPt = Explodes at 129 °C
| ExploLimits = 
| ExternalMSDS = 
| FlashPt = Explodes at 129 °C
| LD50 = 408 mg/kg (oral, mouse)<br>9–70 mg/kg (intraperitoneal mouse, rat); 29 mg/kg (subcutaneous, rat)
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| MainHazards = Toxic<br>Explosive
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| Section7 = {{Chembox Related
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| OtherCompounds = [[Ammonia]]
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}}
'''Hydroxylamine''' is a white crystalline solid, widely used as a reducing agent. It has the chemical formula '''NH<sub>2</sub>OH'''.

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.

==Properties==
===Chemical===
Hydroxylamine reacts with acids to give hydroxylammonium salts.

Reaction with [[copper(II) oxide]] gives [[nitrous oxide]]:
:2 NH<sub>2</sub>OH + 4 CuO → 2 Cu<sub>2</sub>O + N<sub>2</sub>O + 3 H<sub>2</sub>O

===Physical===
Hydroxylamine is a white crystalline solid, hygroscopic and unstable when pure. It is very soluble in water and alcohol.

===Explosive===
Freebase hydroxylamine can explode if heated.

==Availability==
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.

==Preparation==
Hydroxylamine can be prepared through various means:

The Raschig process is the most common route. It involves the reduction of [[ammonium nitrite]] with bisulfite (HSO<sub>3</sub><sup>−</sup>) and [[sulfur dioxide]] at 0 °C in water to hydroxylamido-N,N-disulfonate anion, which hydrolyzes to give hydroxylamine sulfate.

: NH<sub>4</sub>NO<sub>2</sub> + 2 SO<sub>2</sub> + NH<sub>3</sub> + H<sub>2</sub>O → 2 NH<sub>4</sub><sup>+</sup> + N(OH)(OSO<sub>2</sub>)<sub>2</sub><sup>2-</sup>
: N(OH)(OSO<sub>2</sub>)<sub>2</sub><sup>2−</sup> + H<sub>2</sub>O → NH(OH)(OSO<sub>2</sub>)<sup>-</sup> + HSO<sub>4</sub><sup>-</sup>
: 2 NH(OH)(OSO<sub>2</sub>)<sup>−</sup> + 2 H<sub>2</sub>O → (NH<sub>3</sub>OH)<sub>2</sub>SO<sub>4</sub> + SO<sub>4</sub><sup>2-</sup>

To obtain pure hydroxylamine, anhydrous ammonia is added:

:(NH<sub>3</sub>OH)<sub>2</sub>SO<sub>4</sub> + 2 NH<sub>3</sub> → 2 NH<sub>2</sub>OH +(NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub>

Since free hydroxylamine quickly breaks down, the final product is either dissolved in water or reacted with a strong acid, like hydrochloric acid.

Other nitrites, such as [[nitrous acid]] or [[sodium nitrite]] can also be reduced with bisulfite to hydroxylamine.

Electrolytic reduction of [[nitric acid]] with sulfuric acid at 15-20 °C for 40 minutes at 24 A gives hydroxylamine:

:HNO<sub>3</sub> + 3 H<sub>2</sub> → NH<sub>2</sub>OH + 2 H<sub>2</sub>O

Other acids, such as hydrochloric and phosphoric acids can also be used. The yield of this route is between 50-80%.<ref>Schoch, E. P.; Pritchett, R. H.; Journal of the American Chemical Society; vol. 38; (1916); p. 2042</ref>

Electrolysis of [[sodium nitrate]] in the presence of [[hydrogen chloride]] will also give hydroxylamine. A lead cathode and a coal anode are used as electrodes. The process takes 3 hours.<ref>Tafel, J.; Z. Anorg. Chem.; vol. 31; (1902); p. 321 - 324</ref>

Reaction of [[nitrogen dioxide]] or nitrous acid with [[tin(II) chloride]] will give hydroxylamine. The yield is 90%.<ref>[http://onlinelibrary.wiley.com/doi/10.1002/zaac.19261550122/full Raschig, F.; Z. Anorg. Chem.; vol. 155; (1926); p. 225]</ref>

Hydroxylamine can also be made by heating [[nitromethane]] with concentrated [[hydrochloric acid]]. This gives hydroxylamine hydrochloride:

:CH<sub>3</sub>NO<sub>2</sub> + HCl → NH<sub>2</sub>OH·HCl + 2 H<sub>2</sub>O + CO

==Projects==
*Make oximes
*Make hydroxylammonium nitrate
*Purify ketones and aldehydes
*Make [[nitrous oxide]]
*Caprolactam synthesis
*Make Nylon 6
*Make formaldoxime

==Handling==
===Safety===
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.

===Storage===
Hydroxylamine is safe to store only as aqueous solution or in salt form.

===Disposal===
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.

Reduction of hydroxylamine with [[Zinc|Zn]]/[[Hydrochloric acid|HCl]] yields ammonia.

==References==
<references/>
===Relevant Sciencemadness threads===
*[http://www.sciencemadness.org/talk/viewthread.php?tid=1928 Hydroxylamine NH2OH Uses (and Production)]
*[http://www.sciencemadness.org/talk/viewthread.php?tid=8105 How can I test for Hydroxylamine]
*[http://www.sciencemadness.org/talk/viewthread.php?tid=64169 Hydroxylamine synthesis + wargases mumbo jumbo]
*[http://www.sciencemadness.org/talk/viewthread.php?tid=12630 Cheapest Hydroxylamine]
*[http://www.sciencemadness.org/talk/viewthread.php?tid=15176 WTB Hydroxylamine hydrochloride]

[[Category:Chemical compounds]]
[[Category:Inorganic compounds]]
[[Category:Nitrogen compounds]]
[[Category:Bases]]
[[Category:Amines]]
[[Category:Hydroxides]]
[[Category:Energetic materials]]
[[Category:Primary explosives]]