View source for Oxime

{{Short description|1=Organic compounds of the form >C=N–OH}}
{{Use dmy dates|date=February 2023}}
[[File:General structure of oximes.svg|right|250x250px]]

In [[organic chemistry]], an '''oxime''' is an [[organic compound]] belonging to the [[imine]]s, with the general [[Chemical formula|formula]] {{chem2|RR’C\dN\sOH}}, where R is an organic [[Side chain|side-chain]] and R' may be [[hydrogen]], forming an '''aldoxime''', or another organic [[functional group|group]], forming a '''ketoxime'''. O-substituted oximes form a closely related family of compounds. '''Amidoximes''' are oximes of [[amide]]s ({{chem2|R^{1}C(\dO)NR^{2}R^{3} }}) with general structure {{chem2|R^{1}C(\dNOH)NR^{2}R^{3} }}.

Oximes are usually generated by the reaction of [[hydroxylamine]] with [[aldehyde]]s ({{chem2|R\sCH\dO}}) or [[ketone]]s ({{chem2|RR’C\dO}}). The term ''oxime'' dates back to the 19th century, a combination of the words ''oxygen'' and ''imine''.<ref>The name "oxime" is derived from "oximide" (i.e., ''oxy-'' + amide). According to the German organic chemist [[Victor Meyer]] (1848–1897) – who, with Alois Janny, synthesized the first oximes – an "oximide" was an organic compound containing the group ({{chem2|\dN\sOH}}) attached to a carbon atom. The existence of oximides was questioned at the time (ca. 1882). (See page 1164 of:  Victor Meyer und Alois Janny (1882a) [http://gallica.bnf.fr/ark:/12148/bpt6k90694n/f1165.langEN "Ueber stickstoffhaltige Acetonderivate"] (On nitrogenous derivatives of acetone), {{lang|de|Berichte der Deutschen chemischen Gesellschaft}}, '''15''': 1164–1167.) However, in 1882, Meyer and Janny succeeded in synthesizing methylglyoxime ({{chem2|CH3C(\dNOH)CH(\dNOH)}}), which they named "{{lang|de|Acetoximsäure}}" (acetoximic acid) (Meyer & Janny, 1882a, p. 1166). Subsequently, they synthesized 2-propanone, oxime ({{chem2|(CH3)2C\dNOH}}), which they named "{{lang|de|Acetoxim}}" (acetoxime), in analogy with {{lang|de|Acetoximsäure}}. From Victor Meyer and Alois Janny (1882b) [http://gallica.bnf.fr/ark:/12148/bpt6k90694n/f1323.image.langEN "Ueber die Einwirkung von Hydroxylamin auf Aceton"] (On the effect of hydroxylamine on acetone), {{lang|de|Berichte der Deutschen chemischen Gesellschaft}}, '''15''':  1324–1326, page 1324: {{lang|de|"Die Substanz, welche wir, wegen ihrer nahen Beziehungen zur Acetoximsäure, und da sie keine sauren Eigenschaften besitzt, vorläufig Acetoxim nennen wollen, …"}}  (The substance, which we – on account of its close relations to acetoximic acid, and since it possesses no acid properties – will, for the present, name "acetoxime," … )</ref>

==Structure and properties==
If the two side-chains on the central carbon are different from each other—either an aldoxime, or a ketoxime with two different "R" groups—the oxime can often have two different geometric [[stereoisomer]]ic forms according to the [[E/Z configuration|''E''/''Z'' configuration]]. An older terminology of [[Descriptor (chemistry)#syn, anti|''syn'' and ''anti'']] was used to identify especially aldoximes according to whether the R group was closer or further from the hydroxyl.  Both forms are often stable enough to be separated from each other by standard techniques.

Oximes have three characteristic bands in the [[infrared spectroscopy|infrared spectrum]], whose wavelengths corresponding to the stretching vibrations of its three types of bonds: 3600&nbsp;cm<sup>−1</sup> (O−H), 1665&nbsp;cm<sup>−1</sup> (C=N) and 945&nbsp;cm<sup>−1</sup> (N−O).<ref>{{cite web | work = Virtual Textbook of Organic Chemistry | author = Reusch, W. | publisher = [[Michigan State University]] | title = Infrared Spectroscopy | url = http://www.cem.msu.edu/~reusch/VirtTxtJml/Spectrpy/InfraRed/infrared.htm | access-date = 6 July 2009 | archive-url = https://web.archive.org/web/20100621013212/http://www.cem.msu.edu/~reusch/VirtTxtJml/Spectrpy/InfraRed/infrared.htm | archive-date = 21 June 2010 | url-status = dead }}</ref>

In aqueous solution, aliphatic oximes are 10<sup>2</sup>- to 10<sup>3</sup>-fold more resistant to hydrolysis than analogous hydrazones.<ref>{{Cite journal |last1=Kalia |first1=J. |last2=Raines |first2=R. T. |title=Hydrolytic stability of hydrazones and oximes |journal=Angew. Chem. Int. Ed. |year=2008 |volume=47 |pmid=18712739 |issue=39 |pages=7523–7526 |pmc=2743602 |doi=10.1002/anie.200802651}}</ref>

==Preparation==
Oximes can be synthesized by [[condensation reaction|condensation]] of an aldehyde or a ketone with [[hydroxylamine]]. The condensation of aldehydes with hydroxylamine gives aldoximes, and ketoximes are produced from ketones and hydroxylamine. In general, oximes exist as colorless [[crystal]]s or as thick liquids and are poorly soluble in water. Therefore, oxime formation can be used for the identification of [[ketone]] or aldehyde functional groups.

Certain metal salts [[Reduction of nitro compounds#Reduction to oximes|reduce nitro compounds to oximes]].  

Oximes can also be obtained from rearrangement of unstable [[nitroso]] compounds.  Thus [[alkyl nitrite]]s react with [[carbon acid]]s to give oximes: [[methyl ethyl ketone]] with [[ethyl nitrite]],<ref>{{OrgSynth | author = Semon, W. L. | author2 = Damerell, V. R. | name-list-style=amp | title = Dimethoxyglyoxime | collvol = 2 | collvolpages = 204 | year = 1943 | prep = cv2p0204}}</ref> [[propiophenone]] with [[methyl nitrite]],<ref>{{OrgSynth | author = Hartung, Walter H. | author2 = Crossley, Frank | name-list-style=amp | title = Isonitrosopropiophenone | collvol = 2 | collvolpages = 363 | year = 1943 | prep = cv2p0363}}</ref> and [[phenacyl chloride]] with [[butyl nitrite]], all in ethereal [[hydrochloric acid]].<ref>{{OrgSynth | author = Levin, Nathan | author2 = Hartung, Walter H. | name-list-style=amp | title = ω-chloroisonitrosoacetophenone |collvol = 3 | collvolpages = 191 | year = 1955 | prep = cv3p0191}}</ref>  Alternatively, [[sodium nitrite]] in [[glacial acetic acid]] nitrosates [[ethyl acetoacetate]]<ref>{{OrgSynth | author = Fischer, Hans |authorlink=Hans Fischer | title = 2,4-Dimethyl-3,5-dicarbethoxypyrrole | collvol = 2 | collvolpages = 202 | year = 1943 | prep = cv2p0202}}</ref><ref>{{OrgSynth | author = Fischer, Hans | title = Kryptopyrrole | collvol = 3 | collvolpages = 513 | year = 1955 | prep = cv3p0513}}</ref> and [[malononitrile]].<ref>{{OrgSynth | author = Ferris, J. P. | author2 = Sanchez, R. A. | author3 = Mancuso, R. W. | name-list-style=amp | title = Aminomalonitrile p-toluenesulfonate | collvol = 5 | collvolpages = 32 | year = 1973 | prep = cv5p0032}}</ref>

A conceptually related reaction is the [[Japp–Klingemann reaction]].

==Reactions==
The [[hydrolysis]] of oximes proceeds easily by heating in the presence of various [[acid#Common acids|inorganic acid]]s, and the oximes decompose into the corresponding ketones or aldehydes, and hydroxylamines. The reduction of oximes by [[sodium]] metal,<ref>{{cite journal|last1=Suter|first1=C. M.|last2=Moffett|first2=Eugene W.|title=The Reduction of Aliphatic Cyanides and Oximes with Sodium and n-Butyl Alcohol|journal=Journal of the American Chemical Society|date=1934|volume=56|issue=2|pages=487|doi=10.1021/ja01317a502}}</ref> [[sodium amalgam]], [[hydrogenation]], or reaction with [[hydride]] reagents produces [[amine]]s.<ref>{{cite book|author1=George, Frederick |author2=Saunders, Bernard |title=Practical Organic Chemistry |edition=4th|year=1960|publisher=Longman|location=London|isbn=9780582444072|page=93 & 226|url=https://www.scribd.com/doc/46973684/Practical-Organic-Chemistry-Frederick-George-Mann}}</ref> Typically the [[reduction (chemistry)|reduction]] of aldoximes gives both primary amines and secondary amines; however, reaction conditions can be altered (such as the addition of [[potassium hydroxide]] in a 1/30 molar ratio) to yield solely primary amines.<ref>{{cite book|last=Hata|first=Kazuo|title=New Hydrogenating Catalysts|year=1972|publisher=John Wiley & Sons Inc.|location=New York|isbn=9780470358900|page=193|url=https://books.google.com/books?id=5-FEAQAAIAAJ}}</ref>
 
In general, oximes can be changed to the corresponding [[amide]] derivatives by treatment with various acids. This reaction is called [[Beckmann rearrangement]].<ref name="Clayden-2012">{{cite book |last1=Clayden |first1=Jonathan |last2=Greeves |first2=Nick |last3=Warren |first3=Stuart |title=Organic chemistry |date=2012 |publisher=Oxford University Press |isbn=978-0-19-927029-3 |page=958 |edition=2nd}}</ref> In this reaction, a [[hydroxyl group]] is exchanged with the group that is in the anti position of the hydroxyl group. The amide derivatives that are obtained by Beckmann rearrangement can be transformed into a [[carboxylic acid]] by means of hydrolysis (base or acid catalyzed). Beckmann rearrangement is used for the industrial synthesis of [[caprolactam]] (see applications below).

The '''Ponzio reaction''' (1906)<ref>{{cite journal | author = Ponzio, Giacomo | journal = [[J. Prakt. Chem.]] | volume = 73 | pages = 494–496 | year = 1906 | doi = 10.1002/prac.19060730133 | title = Einwirkung von Stickstofftetroxyd auf Benzaldoxim| url = https://zenodo.org/record/1428028 }}</ref> concerning the conversion of ''m''-nitrobenzaldoxime to ''m''-nitrophenyldinitromethane using [[dinitrogen tetroxide]] was the result of research into [[Trinitrotoluene|TNT]] analogues:<ref>{{cite journal | title = Aromatic-Aliphatic Nitro Compounds. III. The Ponzio Reaction; 2,4,6-Trinitrobenzyl Nitrate | author = Fieser, Louis F. | author2 = Doering, William von E. | author2-link = William von E. Doering | name-list-style = amp | journal = [[J. Am. Chem. Soc.]] | year = 1946 | volume = 68 | doi = 10.1021/ja01215a040 | pages = 2252–2253 | issue = 11}}</ref>
[[File:Ponzio Synthesis V2.svg|350px|center|Ponzio reaction]]
Gentler oxidants give mono-nitro compounds.<ref>{{cite journal|last1=Olah|first1=George A.|last2=Ramaiah|first2=Pichika|last3=Chang-Soo|first3=Lee|last4=Prakash|first4=Surya|title=Convenient Oxidation of Oximes to Nitro Compounds with Sodium Perborate in Glacial Acetic Acid|journal=Synlett|date=1992|volume=1992|issue=4|pages=337–339|doi=10.1055/s-1992-22006}}</ref>  

In the [[Neber rearrangement]] certain oximes are converted to the corresponding alpha-amino ketones.

Oximes can be [[dehydration reaction|dehydrated]] using [[acid anhydride]]s to yield corresponding [[nitrile]]s.

Certain amidoximes react with [[benzenesulfonyl chloride]] to make substituted [[urea]]s in the '''Tiemann rearrangement''':<ref>{{cite journal
| author =  Tiemann, Ferdinand |author-link=Ferdinand Tiemann
| title = Ueber die Einwirkung von Benzolsulfonsäurechlorid auf Amidoxime
| pages = 4162–4167
| journal = [[Chemische Berichte]]
| doi = 10.1002/cber.189102402316
| volume = 24
| year = 1891
| issue =  2 
|url=https://zenodo.org/record/1425644
}}</ref><ref>{{cite journal | title = Notes – The Reaction of Phosphorus-Containing Enzyme Inhibitors with Some Hydroxylamine Derivatives |author1=Plapinger, Robert |author2=Owens, Omer | journal = [[J. Org. Chem.]] | doi = 10.1021/jo01116a610 | year = 1956 | volume = 21 | pages = 1186 | issue = 10}}</ref>
:[[File:Tiemann rearragement.png|650px|Tiemann rearragement]]
{{clear left}}

==Uses==
In their largest application, an oxime is an intermediate in the industrial production of [[caprolactam]], a precursor to [[Nylon 6]]. About half of the world's supply of [[cyclohexanone]], more than a million tonnes annually, is converted to the oxime. In the presence of [[sulfuric acid]] [[catalyst]], the oxime undergoes the [[Beckmann rearrangement]] to give the cyclic amide caprolactam:<ref name=Ullmann>{{Ullmann | author1 = Ritz, Josef | author2 = Fuchs, Hugo | author3 = Kieczka, Heinz | author4 = Moran, William C. | title = Caprolactam | doi = 10.1002/14356007.a05_031.pub2}}</ref>
::[[File:Caprolactam Synth.png|340 px]]

===Metal extractant===
[[File:NIMGLO12.png|right|thumb|Structure of [[Nickel bis(dimethylglyoximate)]].]]
Oximes are commonly used as ligands and sequestering agents for metal ions. [[Dimethylglyoxime]] (dmgH<sub>2</sub>) is a reagent for the analysis of nickel and a popular ligand in its own right. In the typical reaction, a metal reacts with two equivalents of dmgH<sub>2</sub> concomitant with ionization of one proton. [[Salicylaldoxime]] is a [[chelator]] in [[hydrometallurgy]].<ref>{{cite journal|author1=Smith, Andrew G. |author2=Tasker, Peter A. |author3=White, David J. |title=The structures of phenolic oximes and their complexes|journal=Coordination Chemistry Reviews|volume=241|issue=1–2 |pages=61–85|doi=10.1016/S0010-8545(02)00310-7|year=2003}}</ref>

Amidoximes such as polyacrylamidoxime can be used to capture trace amounts of [[uranium]] from sea water.<ref>{{cite report|last=Rao|first=Linfeng|title=Recent International R&D Activities in the Extraction of Uranium from Seawater|url=http://escholarship.org/uc/item/12h981cf|publisher=Lawrence Berkeley National Laboratory|date=15 March 2010}}</ref><ref>{{Cite journal|last=Kanno|first=M|title=Present status of study on extraction of uranium from sea water|journal=Journal of Nuclear Science and Technology|volume=21|pages=1–9|doi=10.1080/18811248.1984.9731004|year=1984|issue=1|bibcode=1984JNST...21....1K|doi-access=free}}</ref> In 2017 researchers announced a configuration that absorbed up to nine times as much [[uranyl]] as previous fibers without saturating.<ref>{{Cite web|url=https://www.engadget.com/2017/02/20/endless-nuclear-power-can-be-found-in-the-seas/|title=Endless nuclear power can be found in the seas|last=Dent|first=Steve|date=2017-02-17|publisher=Engadget|access-date=2017-02-22}}</ref>

===Other applications===
* Oxime compounds are used as antidotes for [[nerve agent]]s. A nerve agent inactivates [[acetylcholinesterase]] by phosphorylation. Oxime compounds can reactivate acetylcholinesterase by attaching to phosphorus, forming an oxime-phosphonate, which then splits away from the acetylcholinesterase molecule. Oxime nerve-agent antidotes are [[pralidoxime]] (also known as [[2-PAM]]), [[obidoxime]], methoxime, [[HI-6]], Hlo-7, and [[Trimedoxime bromide|TMB-4]].<ref>{{Cite magazine|author = Rowe, Aaron |title = New Nerve Gas Antidotes|url = http://blog.wired.com/wiredscience/2007/11/building-a-bett.html|magazine = [[Wired (magazine)|Wired]] |date = 27 November 2007}}</ref> The effectiveness of the oxime treatment depends on the particular nerve agent used.<ref>{{cite journal | author = Kassa, J. | year = 2002 | title = Review of oximes in the antidotal treatment of poisoning by organophosphorus nerve agents | journal = Journal of Toxicology: Clinical Toxicology | volume = 40 | pages = 803–16 | doi = 10.1081/CLT-120015840 | pmid = 12475193 | issue = 6| s2cid = 20536869 }}</ref>
* [[Perillartine]], the oxime of [[perillaldehyde]], is used as an artificial sweetener common in Japan.  It is 2000 times sweeter than [[sucrose]].
* Diaminoglyoxime is a key precursor to various compounds containing the highly reactive [[furazan]] ring.
* [[Methyl ethyl ketoxime]] is a skin-preventing additive in many oil-based paints.
* Buccoxime and 5-methyl-3-heptanone oxime ("Stemone") are perfume ingredients.<ref>Johannes Panten and Horst Surburg "Flavors and Fragrances, 2. Aliphatic Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, 2015, Wiley-VCH, Weinheim.{{doi|10.1002/14356007.t11_t01}}</ref>
*[[Fluvoxamine]] is used as an antidepressant.

==See also==
* [[:Category:Oximes]] – specific chemicals containing this functional group
* [[Nitrone]] – the ''N''-oxide of an imine

==References==
{{Reflist}}

{{Antidotes}}
{{Functional group}}
{{Authority control}}

[[Category:Functional groups]]
[[Category:Organic compounds]]
[[Category:Oximes| ]]
[[Category:Chelating agents]]