 | |
 | |
| Names | |
|---|---|
| IUPAC name Azinous acid | |
| Preferred IUPAC name Hydroxylamine (only preselected[1]) | |
Other names
| |
| Identifiers | |
3D model (JSmol) | |
| ChEBI | |
| ChEMBL | |
| ChemSpider |
|
| ECHA InfoCard | 100.029.327 |
| EC Number |
|
| 478 | |
| KEGG |
|
| MeSH | Hydroxylamine |
| RTECS number |
|
| UNII | |
| |
| |
| Properties | |
| NH2OH | |
| Molar mass | 33.030 g·mol−1 |
| Appearance | Vivid white, opaque crystals |
| Density | 1.21 g cm−3 (at 20 °C)[2] |
| Melting point | 33 °C (91 °F; 306 K) |
| Boiling point | 58 °C (136 °F; 331 K) /22 mm Hg (decomposes) |
| Soluble | |
| logP | −0.758 |
| Acidity (pKa) | 6.03 ([NH3OH]+) |
| Basicity (pKb) | 7.97 |
| Structure | |
| Tricoordinated at N, dicoordinated at O | |
| Trigonal pyramidal at N,bent at O | |
| 0.67553 D | |
| Thermochemistry | |
| 46.47 J/(K·mol) | |
Std molar entropy(S⦵298) | 236.18 J/(K·mol) |
Std enthalpy of formation(ΔfH⦵298) | −39.9 kJ/mol |
| Hazards | |
| GHS labelling: | |
     | |
| Danger | |
| H200,H290,H302,H312,H315,H317,H318,H335,H351,H373,H400 | |
| P201,P202,P234,P260,P264,P270,P271,P272,P273,P280,P281,P301+P312,P302+P352,P304+P340,P305+P351+P338,P308+P313,P310,P312,P314,P321,P322,P330,P332+P313,P333+P313,P362,P363,P372,P373,P380,P390,P391,P401,P403+P233,P404,P405,P501 | |
| NFPA 704 (fire diamond) | |
| Flash point | 129 °C (264 °F; 402 K) |
| 265 °C (509 °F; 538 K) | |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | 408 mg/kg (oral, mouse); 59–70 mg/kg (intraperitoneal mouse, rat); 29 mg/kg (subcutaneous, rat)[3] |
| Safety data sheet (SDS) | ICSC 0661 |
| Related compounds | |
Related hydroxylammonium salts | |
Related compounds | |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Hydroxylamine (also known ashydroxyammonia) is aninorganic compound with thechemical formulaNH2OH. The compound exists ashygroscopic colorlesscrystals.[4] Hydroxylamine is almost always provided and used as either anaqueous solution or, more often, as one of its salts, such ashydroxylammonium sulfate, a water-soluble solid.
Hydroxylamine and its salts are consumed almost exclusively to produceNylon-6. Theoxidation ofNH3 to hydroxylamine is a step in biologicalnitrification.[5]
Hydroxylamine was first prepared ashydroxylammonium chloride in 1865 by the German chemistWilhelm Clemens Lossen (1838-1906); he reactedtin andhydrochloric acid in the presence ofethyl nitrate.[6] It was first prepared in pure form in 1891 by the Dutch chemistLobry de Bruyn and by the French chemist Léon Maurice Crismer (1858-1944).[7][8] Thecoordination complexZnCl2(NH2OH)2 (zinc dichloride di(hydroxylamine)), known as Crismer's salt, releases hydroxylamine upon heating.[9]
Hydroxylamine and itsN-substituted derivatives are pyramidal at nitrogen, with bond angles very similar to those of amines. The most stable conformation of hydroxylamine has the NOH anti to the lone pair on nitrogen, seeming to minimize the repulsion between the nitrogen and oxygen lone pairs.[10]
Hydroxylamine or itssalts (salts containing hydroxylammoniumcations[NH3OH]+) can be produced via several routes but only two are commercially viable. It is also produced naturally as discussed in a section onbiochemistry.
NH2OH is mainly produced as itssulfuric acidsalt, hydroxylammonium sulfate ([NH3OH][SO4]), by thehydrogenation ofnitric oxide overplatinumcatalysts in the presence of sulfuric acid.[11]
Another route toNH2OH is theRaschig process:aqueousammonium nitrite isreduced byHSO−3 andSO2 at 0 °C to yield a hydroxylamido-N,N-disulfonateanion:
This ammonium hydroxylamine disulfonate anion is thenhydrolyzed to givehydroxylammonium sulfate:
Julius Tafel discovered that hydroxylaminehydrochloride orsulfate salts can be produced byelectrolytic reduction ofnitric acid withHCl orH2SO4 respectively:[12][13]
Hydroxylamine can also be produced by the reduction ofnitrous acid orpotassium nitrite withbisulfite:
Hydrochloric acid disproportionatesnitromethane tohydroxylamine hydrochloride andcarbon monoxide viathe hydroxamic acid.[citation needed]
A direct lab synthesis of hydroxylamine frommolecular nitrogen inwater plasma was demonstrated in 2024.[14]
SolidNH2OH can be collected by treatment withliquid ammonia.Ammonium sulfate,[NH4]2SO4, a side-product insoluble in liquid ammonia, is removed by filtration; the liquidammonia is evaporated to give the desired product.[4]The net reaction is:
Base, such as sodium butoxide, can be used to free the hydroxylamine fromhydroxylammonium chloride:[4]
Hydroxylamine is a base with apKa of 6.03:
Hydroxylamine reacts withalkylating agents usually at thenitrogen atom:
The reaction ofNH2OH with analdehyde orketone produces anoxime.
This reaction can be useful in the purification of ketones and aldehydes: if hydroxylamine is added to an aldehyde or ketone in solution, an oxime forms, which generally precipitates from solution; heating the precipitate with aqueous acid then restores the original aldehyde or ketone.[15]
NH2OH reacts withchlorosulfonic acid to givehydroxylamine-O-sulfonic acid:[16]
In aqueous solution, hydroxylamine is predicted to coexist with atautomer, theamine oxideH3N+−O− (ammonia oxide).[17] The solvated ammonia oxide form has variously been estimated to be less stable by 0.9–3.5 kcal·mol-1.[18] It is absent from the gas phase, where the predicted stability gap is 27.6 kcal·mol-1.[19]
Hydroxylamine derivativessubstituted in place of the hydroxyl or amine hydrogen are (respectively) calledO- orN‑hydroxylamines. In generalN‑hydroxylamines are more common. Examples areN‑tert‑butylhydroxylamine or theglycosidic bond incalicheamicin.N,O‑Dimethylhydroxylamine is a precursor toWeinreb amides.
Similarly to amines, one can distinguish hydroxylamines by their degree of substitution: primary, secondary and tertiary. When stored exposed to air for weeks, secondary hydroxylamines degrade tonitrones.[20]
N‑organylhydroxylamines,R−NH−OH, where R is anorganyl group, can be reduced toaminesR−NH2:[21]
Oximes such asdimethylglyoxime are also employed asligands.
The hydrolysis of N-substituted oximes, hydroxamic acids, and nitrones easily provides hydroxylamines.
Alkylating of hydroxylamine or N-alkylhydroxylamines proceeds usually at nitrogen. One challenge is dialkylation when only monoalkylation is desired.
For O-alkylation of hydroxylamines, strong base such assodium hydride is required to first deprotonate the OH group:[22]
Amine oxidation withbenzoyl peroxide is a common method to synthesize hydroxylamines. Care must be taken to prevent over-oxidation to anitrone. Other methods include:
.png)
Approximately 95% of hydroxylamine is used in the synthesis ofcyclohexanone oxime, a precursor toNylon 6.[11] The treatment of this oxime with acid induces theBeckmann rearrangement to givecaprolactam.[23] The latter can then undergo a ring-opening polymerization to yield Nylon 6.[24]
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.
High concentrations of hydroxylamine are used by biologists to introducemutations by acting as a DNAnucleobase amine-hydroxylating agent.[25] In is thought to mainly act via hydroxylation ofcytidine to hydroxyaminocytidine, which is misread as thymidine, thereby inducing C:G to T:A transition mutations.[26] But high concentrations or over-reaction of hydroxylaminein vitro are seemingly able to modify other regions of the DNA & lead to other types of mutations.[26] This may be due to the ability of hydroxylamine to undergo uncontrolled free radical chemistry in the presence of trace metals and oxygen, in fact in the absence of its free radical effectsErnst Freese noted hydroxylamine was unable to induce reversion mutations of its C:G to T:A transition effect and even considered hydroxylamine to be the most specific mutagen known.[27] Practically, it has been largely surpassed by more potent mutagens such asEMS,ENU, ornitrosoguanidine, but being a very small mutagenic compound with high specificity, it found some specialized uses such as mutation of DNA packed withinbacteriophage capsids,[28] and mutation of purified DNAin vitro.[29]
Analternative industrial synthesis of paracetamol developed byHoechst–Celanese involves the conversion ofketone to aketoxime with hydroxylamine.
Some non-chemical uses include removal of hair from animal hides and photographic developing solutions.[2] In the semiconductor industry, hydroxylamine is often a component in the "resist stripper", which removes photoresist after lithography.
Hydroxylamine can also be used to better characterize the nature of a post-translational modification onto proteins. For example, poly(ADP-Ribose) chains are sensitive to hydroxylamine when attached to glutamic or aspartic acids but not sensitive when attached to serines.[30] Similarly, Ubiquitin molecules bound to serines or threonines residues are sensitive to hydroxylamine, but those bound to lysine (isopeptide bond) are resistant.[31]
In biological nitrification, the oxidation ofNH3 to hydroxylamine is mediated by theammonia monooxygenase (AMO).[5]Hydroxylamine oxidoreductase (HAO) further oxidizes hydroxylamine to nitrite.[32]
Cytochrome P460, anenzyme found in theammonia-oxidizing bacteriaNitrosomonas europea, can convert hydroxylamine tonitrous oxide, a potentgreenhouse gas.[33]
Hydroxylamine can also be used to highly selectively cleaveasparaginyl-glycine peptide bonds in peptides and proteins.[34] It also bonds to and permanently disables (poisons)heme-containing enzymes. It is used as an irreversible inhibitor of theoxygen-evolving complex of photosynthesis on account of its similar structure to water.
Hydroxylamine is a skin irritant but is of low toxicity.
Adetonator can easily explode aqueous solutions concentrated above 80% by weight, and even 50% solution might prove detonable if tested in bulk.[35][36] In air, the combustion is rapid and complete:
Absent air, pure hydroxylamine requires stronger heating and the detonation does not complete combustion:
At least two factories dealing in hydroxylamine have been destroyed since 1999 with loss of life.[37] It is known, however, that ferrous and ferriciron salts accelerate the decomposition of 50%NH2OH solutions.[38] Hydroxylamine and its derivatives are more safely handled in the form ofsalts.
It is an irritant to therespiratory tract, skin, eyes, and othermucous membranes. It may be absorbed through the skin, is harmful if swallowed, and is a possiblemutagen.[39]
manufacture of chemicals by electrolysis hydroxylamine 32.
| International | |
|---|---|
| National | |
| Other | |
