Hydroxylamine

Hydroxylamine
IUPAC name Hydroxylamine
Systematic name Hydroxylamine[1]
Other names Aminol Azanol Hydroxyamine Hydroxyazane Hydroxylazane Nitrinous acid
Identifiers
CAS number	7803-49-8 Y
PubChem	787
ChemSpider	766 Y
UNII	2FP81O2L9Z N
EC number	232-259-2
KEGG	C00192 Y
MeSH	Hydroxylamine
ChEBI	CHEBI:15429 Y
ChEMBL	CHEMBL1191361 N
RTECS number	NC2975000
Gmelin Reference	478
3DMet	B01184
Jmol-3D images	Image 1 Image 2
SMILES NO ON
InChI InChI=1S/H3NO/c1-2/h2H,1H2 Y Key: AVXURJPOCDRRFD-UHFFFAOYSA-N Y InChI=1/H3NO/c1-2/h2H,1H2 Key: AVXURJPOCDRRFD-UHFFFAOYAD
Properties
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
Structure
Coordination geometry	Trigonal at N
Molecular shape	Tetrahedral at N
Dipole moment	0.67553 D
Thermochemistry
Std enthalpy of formation ΔfHo298	-39.9 kJ mol-1
Standard molar entropy So298	236.18 J K-1 mol-1
Specific heat capacity, C	46.47 J K-1 mol-1
Hazards
MSDS	ICSC 0661
EU Index	612-122-00-7
EU classification	E Xn Xi N
R-phrases	R2, R21/22, R37/38, R40, R41, R43, R48/22, R50
S-phrases	(S2), S26, S36/37/39, S61
NFPA 704	1 2 3
Flash point	129 °C
Autoignition temperature	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 Hydrazine
N (verify) (what is: Y/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).

Production

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⁻

Reactions

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

R-X + NH₂OH → R-ONH₂ + HX

R-X + NH₂OH → R-NHOH + 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.

HOSO₂Cl + NH₂OH → NH₂OSO₂OH + HCl

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

Uses

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.

Safety

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

• Amine

References

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

• Calorimetric studies of hydroxylamine decomposition
• Chemical company BASF info
• MSDS
• MSDS
• Deadly detonation of hydroxylamine at Concept Sciences facility