Hydroxylamine

Hydroxylamine.jpgslightly soluble in ether, benzene,
chloroform, carbon disulfide formation]] R: 5-22-37/38-41-43-48/22-50

S: (2-)-22-26-36/37/39-61

nfpa_f3.png nfpa_r1.pngHydroxylamine sulfate

Hydroxylamine
General
Systematic name	hydroxylamine
Molecular formula	NH₂OH
Molar mass	33.0298
Appearance	white needles or flakes
CAS number	CAS=-->7803-49-8
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
Melting point	33 °C
Boiling point	110 °C
Structure
Dipole moment	0.67553 debye
Thermodynamic data
Standard enthalpy of	-39.9 kJ/mol
Standard molar entropy	? J·K⁻¹·mol⁻¹
Hazards
EU classification	Symbol: Xn, N
NFPA 704
Supplementary data page
Spectral data	UV, IR, NMR, MS
Related compounds
Related compounds	Hydroxylamine hydrochloride
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Chemical infobox

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; 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).

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 → ^*₂^*

2)₂" target="_blank" >^*^2-" target="_blank" >+ H₂O → 2)" target="_blank" >^*" target="_blank" >+ ^*

22)" target="_blank" >^*^-" target="_blank" >+ 2H₂O → 4" target="_blank" >^*" target="_blank" >+ ^*

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.

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^- → + H₂O → ^*^-

+ H₃O⁺ (100 °C/1 h) → ^*^-

^*Cl + NaOBu → NH₂OH + NaCl + BuOH

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.

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.

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 in genomes which switch base pairs from A to G, or from C to T. This is to probe functional areas of genes to "see" what happens if their functions are broken. In recent times other methods of random mutations have been used.

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.

References

Hydroxylamine Walters, Michael A. and Andrew B. Hoem. "Hydroxylamine." e-Encyclopedia of Reagents for Organic Synthesis. 2001.

Greenwood and Earnshaw. Chemistry of the Elements. 2^nd Edition. Reed Educational and Professional Publishing Ltd. pp. 431-432. 1997.

MSDS Sigma-Aldrich

Schupf Computational Chemistry Lab

Patnaik, Pradyot. Handbook of Inorganic Chemicals. McGraw Hill. pp. 385-386. 2003.

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).

External links

Functional groups | Amines | Hydroxides | Photographic chemicals | Rocket fuels