Hydroxylamine
| Hydroxylamine | |
|---|---|
 |
 |
 | |
| IUPAC name | hydroxylamine |
| Identifiers | |
| CAS number | [7803-49-8] |
| PubChem | |
| SMILES | NO |
| Properties | |
| Molecular formula | NH2OH |
| Molar mass | 33.0298 g/mol |
| Appearance | white needles or flakes |
| Density | 1.21 g cm−3 |
| Melting point |
33 °C |
| Boiling point |
110 °C |
| Solubility in water | soluble in cold water, decomposes in hot water |
| Structure | |
| Dipole moment | 0.67553 debye |
| Thermochemistry | |
| Std enthalpy of formation ΔfH |
−39.9 kJ/mol |
| Standard molar entropy S |
? J K−1 mol−1 |
| Hazards | |
| EU classification | Xn, N |
| NFPA 704 |
 3
3
1
|
| R-phrases | R5, R22, R37/38, R41, R43, R48/22, R50 |
| S-phrases | (S2), S22, S26, S36/37/39, S61 |
| 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;[1] 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.[2] It is known, however, that ferrous and ferric iron salts 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 biological nitrification. The oxidation of NH3 is mediated by hydroxylamine oxidoreductase (HAO).
Production
NH2OH can be synthesized 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]
- NH4NO2 + 2SO2 + NH3 + H2O → [NH4]2[N(OH)(OSO2)2]
-
- 2[NH4]+[NH(OH)(OSO2)]− + 2H2O → [NH3(OH)]2[SO4] + [NH4]2[SO4]
Solid NH2OH can be collected by treatment with liquid ammonia. Ammonium sulfate is insoluble in liquid ammonia and is removed by filtration; the liquid ammonia is evaporated to give the desired product.[1]
Another method of synthesis is to make hydroxylammonium salts which can then be converted to hydroxylamine.
-
- [NH3(OH)]Cl + NaOBu → NH2OH + NaCl + BuOH[1]
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]−
Reactions
Hydroxylamine reacts with electrophiles, such as an alkylating agents, which can attach at either the O or N position.
-
- R-X + NH2OH → R-ONH2 + HX
- R-X + NH2OH → R-NHOH + HX
- R-X + NH2OH → R-ONH2 + 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 be checked by iodometric titration.
Hydroxylamine (NH2OH), or hydroxylamines (R-NHOH) can be reduced to amines.[3]
-
- NH2OH (Zn/HCl) → NH3
- R-NHOH (Zn/HCl) → R-NH2
- NH2OH (Zn/HCl) → NH3
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.[4]
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.
This has also been used in the past by biologists to introduce random mutations by switching base pairs from A to G, or from C to T. This is to probe functional areas of genes to elucidate what happens if their functions are broken. Nowadays other mutagens are used. Hydroxylamine can also be used to highly selectively cleave asparaginyl-glycine peptide bonds in peptides and proteins. It also bonds to and permanently disables (poisons) heme-containing enzymes. It is used as an irreversible inhibitor of the oxygen-evolving complex of photosynthesis on account of its similar structure to water.
In the semiconductor industry, hydroxylamine is often a component in the "resist stripper" which removes photoresist after lithography.
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.[5]
See also
- Amine
References
- a b c Greenwood and Earnshaw. Chemistry of the Elements. 2nd Edition. Reed Educational and Professional Publishing Ltd. pp. 431-432. 1997.
- Japan Science and Technology Agency Failure Knowledge Database.
- Smith, Michael and Jerry March. March's advanced organic chemistry : reactions, mechanisms, and structure. New York. Wiley. p. 1554. 2001.
- Patnaik, Pradyot. Handbook of Inorganic Chemicals. McGraw Hill. pp. 385-386. 2003.
- MSDS Sigma-Aldrich
- Hydroxylamine
- Schupf Computational Chemistry Lab
- 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).
External links
- Calorimetric studies of hydroxylamine decomposition
- Chemical company BASF info
- MSDS
- MSDS
- Deadly detonation of hydroxylamine at Concept Sciences facility
Source: adapted by the editor from Wikipedia, the free encyclopedia; from the article "Hydroxylamine". Image Credit.
