CAS number 7803-49-8 YesY
PubChem 787
ChemSpider 766 YesY
EC number 232-259-2
KEGG C00192 YesY
MeSH Hydroxylamine
ChEBI CHEBI:15429 YesY
RTECS number NC2975000
Gmelin Reference 478
3DMet B01184
Jmol-3D images Image 1
Image 2
Molecular formula H3NO
Molar mass 33.03 g mol−1
Exact mass 33.021463723 g mol-1
Appearance Vivid white, opaque crystals
Density 1.21 g cm-3 (at 20 °C)[2]
Melting point

33 °C, 306 K, 91 °F

Boiling point

58 °C, 331 K, 136 °F (decomposes)

log P -0.758
Acidity (pKa) 13.7
Basicity (pKb) 0.3
Trigonal at N
Molecular shape Tetrahedral at N
Dipole moment 0.67553 D
Std enthalpy of
-39.9 kJ mol-1
Standard molar
236.18 J K-1 mol-1
Specific heat capacity, C 46.47 J K-1 mol-1
EU Index 612-122-00-7
EU classification E Harmful Xn Irritant Xi Dangerous for the Environment (Nature) N
R-phrases R2, R21/22, R37/38, R40, R41, R43, R48/22, R50
S-phrases (S2), S26, S36/37/39, S61
NFPA 704
NFPA 704.svg
Flash point 129 °C
265 °C
LD50 408 mg/kg (oral, mouse); 59–70 mg/kg (intraperitoneal mouse, rat); 29 mg/kg (subcutaneous, rat)[3]
Related compounds
Related hydroxylammonium salts Hydroxylammonium chloride
Hydroxylammonium nitrate
Hydroxylammonium sulfate
Related compounds Ammonia


 N (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Hydroxylamine is an inorganic compound with the formula NH2OH. The pure material is a white, unstable crystalline, hygroscopic compound.[4] However, hydroxylamine is almost always provided and used as an aqueous solution. It is used to prepare oximes, an important functional group. It is also an intermediate in biological nitrification. The oxidation of NH3 is mediated by the enzyme hydroxylamine oxidoreductase (HAO).



NH2OH can be produced via several routes. The main route is via Raschig synthesis: aqueous ammonium nitrite is reduced by HSO4 and SO2 at 0 °C to yield a hydroxylamido-N,N-disulfate anion:

NH4NO2 + 2 SO2 + NH3 + H2O → 2 NH4+ + N(OH)(OSO2)22−

This anion is then hydrolyzed to give (NH3OH)2SO4:

N(OH)(OSO2)22− + H2O → NH(OH)(OSO2) + HSO4
2 NH(OH)(OSO2) + 2 H2O → (NH3OH)2SO4

Solid NH2OH can be collected by treatment with liquid ammonia. Ammonium sulfate, (NH4)2SO4, a side-product insoluble in liquid ammonia, is removed by filtration; the liquid ammonia is evaporated to give the desired product.[4]

Hydroxylammonium salts can then be converted to hydroxylamine by neutralization:

(NH3OH)Cl + NaOBu → NH2OH + NaCl + BuOH[4]

Hydroxylamine can also be produced by the reduction of nitrous acid or potassium nitrite with bisulfite:

HNO2 + 2 HSO3 → N(OH)(OSO2)22− + H2O → NH(OH)(OSO2) + HSO4
NH(OH)(OSO2) + H3O+ (100 °C/1 h) → NH3(OH)+ + HSO4


Hydroxylamine reacts with electrophiles, such as alkylating agents, which can attach to either the oxygen or the nitrogen:

R-X + NH2OH → R-ONH2 + HX

The reaction of NH2OH with an aldehyde 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.[clarification needed] Oximes, e.g., dimethylglyoxime, are also employed as ligands.

NH2OH reacts with chlorosulfonic acid to give hydroxylamine-O-sulfonic acid, a useful reagent for the synthesis of caprolactam.


The hydroxylamine-O-sulfonic acid, which should be stored at 0 °C to prevent decomposition, can be checked by iodometric titration.[clarification needed]

Hydroxylamine (NH2OH), or hydroxylamines (R-NHOH) can be reduced to amines.[5]

NH2OH (Zn/HCl) → NH3
R-NHOH (Zn/HCl) → R-NH2

Hydroxylamine explodes with heat:

4 NH2OH + O2 → 2 N2 + 6 H2O


Hydroxylamine and its salts are commonly used as reducing agents in myriad 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.[2]

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 G to A, 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.


Hydroxylamine may explode on heating. The nature of the explosive hazard is not well understood. At least two factories dealing in hydroxylamine have been destroyed since 1999 with loss of life.[6] It is known, however, that ferrous and ferric iron salts accelerate the decomposition of 50% NH2OH solutions.[7] Hydroxylamine and its derivatives are more safely handled in the form of salts.

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.[8]

Functional group

Substituted derivatives of hydroxylamine are known. If the hydroxyl hydrogen is substituted, this is called an O-hydroxylamine, if one of the amine hydrogens is substituted, this is called an N-hydroxylamine. Smilarly to ordinary amines, one can distinguish primary, secondary and tertiary hydroxylamines, the latter two referring to compounds where two or three hydrogens are substituted, respectively. Examples of compounds containing a hydroxylamine functional group are N-tert-butyl-hydroxylamine or the glycosidic bond in calicheamicin. N,O-Dimethylhydroxylamine is a coupling agent, used to synthesize Weinreb amides.

See also


  1. ^ "Hydroxylamine - PubChem Public Chemical Database". The PubChem Project. USA: National Center for Biotechnology Information. http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=787. 
  2. ^ a b Lide, David R., ed (2006). CRC Handbook of Chemistry and Physics (87th ed.). Boca Raton, FL: CRC Press. ISBN 0-8493-0487-3. 
  3. ^ Martel, B.; Cassidy, K. (2004). Chemical Risk Analysis: A Practical Handbook. Butterworth–Heinemann. pp. 362. ISBN 1903996651. 
  4. ^ a b c Greenwood and Earnshaw. Chemistry of the Elements. 2nd Edition. Reed Educational and Professional Publishing Ltd. pp. 431-432. 1997.
  5. ^ Smith, Michael and Jerry March. March's advanced organic chemistry : reactions, mechanisms, and structure. New York. Wiley. p. 1554. 2001.
  6. ^ Japan Science and Technology Agency Failure Knowledge Database.
  7. ^ Cisneros, L.O., Rogers, W.J., Mannan, M.S., Li, X and Koseki, H. “ Effect of Iron Ion in the Thermal Decomposition of 50 mass% Hydroxylamnie/Water Solutions” J. Chem. Eng Data 48(5), (2003) 1164-1169.
  8. ^ MSDS Sigma-Aldrich

Further reading

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

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Look at other dictionaries:

  • hydroxylamine — [ idrɔksilamin ] n. f. • 1873; de hydroxyle et amine ♦ Chim. Base dérivée de l ammoniac (NH2OH). ● hydroxylamine nom féminin Dérivé hydroxylé de l ammoniac, de formule HO―NH2. (Solide fondant à 33 °C, très soluble dans l eau, l hydroxylamine n… …   Encyclopédie Universelle

  • Hydroxylamine — Hy*drox yl*am ine, n. [Hydroxyl + amine.] (Chem.) A nitrogenous, organic base, {NH2.OH}, resembling ammonia, and produced by a modified reduction of nitric acid. It is usually obtained as a volatile, unstable solution in water. It acts as a… …   The Collaborative International Dictionary of English

  • hydroxylamine — hydroxylamine. См. гидроксиламин. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • hydroxylamine — [hī dräks΄il ə mēn′, hī dräks΄ilam′ēn΄; hī dräks΄il am′in] n. [ HYDROXYL + AMINE] a colorless crystalline base, NH2OH, used as a reducing agent …   English World dictionary

  • hydroxylamine — /huy drok seuh leuh meen , seuhl am in/, n. an unstable, weakly basic, crystalline compound, NH3O, used as a reducing agent, analytical reagent, and chemical intermediate. [1865 70; HYDROXYL + AMINE] * * * ▪ chemical compound       (NH2OH), an… …   Universalium

  • Hydroxylamine — Les hydroxylamines sont les composés dont la formule est NR1R2 OH elles dérivent de l hydroxylamine de formule NH2OH.Les hydroxylamines sont aussi des outils chimique utile pour des coupures spécifique de peptides , ils rompent la liaison entre… …   Wikipédia en Français

  • hydroxylamine- — hidroksilamin statusas T sritis chemija apibrėžtis Ligandas. formulė NH₂OH atitikmenys: angl. hydroxylamine rus. гидроксиламин ryšiai: sinonimas – hidroksazan …   Chemijos terminų aiškinamasis žodynas

  • hydroxylamine — hidroksilaminas statusas T sritis chemija formulė NH₂OH atitikmenys: angl. hydroxylamine rus. гидроксиламин ryšiai: sinonimas – hidroksazanas …   Chemijos terminų aiškinamasis žodynas

  • Hydroxylamine reductase (NADH) — In enzymology, a hydroxylamine reductase (NADH) (EC number| is an enzyme that catalyzes the chemical reaction:NH3 + NAD+ + H2O ightleftharpoons hydroxylamine + NADH + H+The 3 substrates of this enzyme are NH3, NAD+, and H2O, whereas its… …   Wikipedia

  • Hydroxylamine oxidase — In enzymology, a hydroxylamine oxidase (EC number| is an enzyme that catalyzes the chemical reaction:hydroxylamine + O2 ightleftharpoons nitrite + H2OThus, the two substrates of this enzyme are hydroxylamine and O2, whereas its two… …   Wikipedia

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