Hydroxylamine
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| Hydroxylamine | |
|---|---|
| Image:Hydroxylamine3D.jpg Image:Hydroxylamine.jpg | |
| General | |
| Systematic name | hydroxylamine |
| Molecular formula | NH2OH |
| Molar mass | 33.0298 |
| Appearance | white needles or flakes |
| CAS number | Properties |
| Density and phase | 1.21g/cm3 |
| Solubility in water | soluble in cold water, decomposes in hot water |
| Solubility in other solvents | soluble in methanol, liquid NH3
slightly soluble in ether, benzene, |
| Melting point | 33°C |
| Boiling point | 110°C |
| Structure | |
| Dipole moment | 0.67553 Debye |
| Thermodynamic data | |
| Standard enthalpy of formation | -39.9kJ/mol |
| Standard molar entropy | ? J.K−1.mol−1 |
| Hazards | |
| EU classification | Symbol: Xn, N
R: 5-22-37/38-41-43-48/22-50 S: (2-)-22-26-36/37/39-61 |
| NFPA 704 | Image:Nfpa h3.pngImage:Nfpa f3.pngImage:Nfpa r1.png |
| Supplementary data page | |
| Spectral data | UV, IR, NMR, MS |
| Related compounds | |
| Related compounds | Hydroxylamine Hydrochloride
Hydroxylamine Sulfate |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references | |
Hydroxylamine is a reactive chemical with formula NH2OH. It can be considered a hybrid of ammonia and water due to parallels it shares with each. At room temperature pure NH2OH is ordinarily a white, unstable crystalline, hygroscopic compound; Template:Ref however it is almost always encountered as an aqueous solution.
Hydroxylamine tends to be explosive, and the nature of the hazard is not entirely understood. At least two factories dealing in hydroxylamine have been destroyed since 1999 with loss of life. It is known, however, that ferrous and ferric iron accelerate the decomposition of 50% NH2OH solutions. Hydroxylamine and its derivatives are more safely handled in the form of salts.
NH2OH is an intermediate in the biological nitrification. The oxidation of NH3 is mediated by HAO (hydroxylamine oxidoreductase).
Contents |
Production
'NH2OH can be synthesizing via several routes:
Raschig Synthesis: Aqueous ammonium nitrite is reduced by HSO4-/SO2 at 0 °C to yield a hydroxylamido-N,N-disulfate anion, which can be hydrolyzed to give (NH3OH)2SO4.
- NH4NO2 + 2SO2 + NH3 + H2O → [NH4]2[N(OH)(OSO2)2]
- [NH4]+2[N(OH)(OSO2)2]2- + H2O → [NH4][NH(OH)(OSO2)] + [NH4][HSO4]
- 2[NH4]+[NH(OH)(OSO2)]- + 2H2O → [NH3(OH)]2[SO4] + [NH4]2[SO4]
Solid NH2OH can be collected by treatment with NH3 (l). Ammonium sulfate is insoluble in NH3, and can be filtered from the solution, and the liquid ammonia can then removed by vacuum to give the desired product.Template:Ref
Another method of synthesis is to make hydroxylammonium salts which can then be converted to hydroxylamine.
The reduction of nitrous acid or potassium nitrate with bisulfite:
- HNO2 + 2 HSO3- → [N(OH)(OSO2)2]2- + H2O → [NH(OH)(OSO2)]- + [HSO4]-
- [NH(OH)(OSO2)]- + H3O+ (100 °C/1 h) → [NH3(OH)]+ + [HSO4]-
- [NH3(OH)]Cl + NaOBu → NH2OH + NaCl + BuOHTemplate:Ref
Reactions
Hydroxylamine reacts with electrophiles, such as an alkylating agents, which can attack at either the O or N position.
- R-X + NH2OH → R-ONH2 + HX
- R-X + NH2OH → R-NHOH + HX
The reaction of NH2OH with an aldyhyde or ketone produces an oxime.
- R2C=O + NH2OH∙HCl , NaOH → R2C=NOH + NaCl + H2O
This reaction is useful in the purification of ketones and aldehydes, Oximes also are employed as ligands, e.g. dimethylglyoxime.
NH2OH reacts with chlorosulfuric acid to give hydroxylamine-O-sulfonic acid, a useful reagent for the synthesis of caprolactam.
- HOSO2Cl + NH2OH → NH2OS2OH + HCl
The hydroxylamine-O-sulfonic acid, which should be stored at 0 °C, can checked by iodometric titration.
Hydroxylamine (NH2OH), or hydroxylamines (R-NHOH) can be reduced to amines.Template:Ref
- NH2OH (Zn/HCl) → NH3
- R-NHOH (Zn/HCl) → R-NH2
Uses
Hydroxylamine and its salts are commonly used as reducing agents in a myriad of organic and inorganic reactions. They can also act as antioxidants for fatty acids. Some non-chemical uses include removal of hair from animal hides and photography developing solutions.Template:Ref
The nitrate salt, hydroxylammonium nitrate, is being researched as a rocket propellant, both in water solution as a monopropellant and in its solid form as a solid propellant.
Safety
Hydroxylamine may explode on heating. It is an irritant to the respiratory tract, skin, eyes, and other mucous membranes. It may be absorbed through the skin, is harmful if swallowed, and is a possible mutagen.Template:Ref
References
Template:NoteHydroxylamine Walters, Michael A. and Andrew B. Hoem. "Hydroxylamine." e-Encyclopedia of Reagents for Organic Synthesis. 2001.
Template:Note Greenwood and Earnshaw. Chemistry of the Elements. 2nd Edition. Reed Educational and Professional Publishing Ltd. pp. 431-432. 1997.
Template:Note MSDS Sigma-Aldrich
Template:Note Schupf Computational Chemistry Lab
Template:Note Patnaik, Pradyot. Handbook of Inorganic Chemicals. McGraw Hill. pp. 385-386. 2003.
Template:Note Smith, Michael and Jerry March. March's advanced organic chemistry : reactions, mechanisms, and structure. New York. Wiley. p. 1554. 2001.
M. W. Rathke A. A. Millard "Boranes in Functionalization of Olefins to Amines: 3-Pinanamine" Organic Syntheses, Coll. Vol. 6, p.943; Vol. 58, p.32. (preparation of hydroxylamine-O-sulfonic acid).