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In organic chemistry, an oxime is an organic compound belonging to the , with the general Chemical formula , where R is an organic Side chain and R' may be hydrogen, forming an aldoxime, or another organic functional group, forming a ketoxime. O-substituted oximes form a closely related family of compounds. Amidoximes are oximes of () with general structure .
Oximes are usually generated by the reaction of hydroxylamine with () or (). The term oxime dates back to the 19th century, a combination of the words oxygen and imine.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 () 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) "Ueber stickstoffhaltige Acetonderivate" (On nitrogenous derivatives of acetone), Berichte der Deutschen chemischen Gesellschaft, 15: 1164–1167.) However, in 1882, Meyer and Janny succeeded in synthesizing methylglyoxime (), which they named "Acetoximsäure" (acetoximic acid) (Meyer & Janny, 1882a, p. 1166). Subsequently, they synthesized 2-propanone, oxime (), which they named "Acetoxim" (acetoxime), in analogy with Acetoximsäure. From Victor Meyer and Alois Janny (1882b) "Ueber die Einwirkung von Hydroxylamin auf Aceton" (On the effect of hydroxylamine on acetone), Berichte der Deutschen chemischen Gesellschaft, 15: 1324–1326, page 1324: "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," … )
Oximes have three characteristic bands in the infrared spectrum, whose wavelengths corresponding to the stretching vibrations of its three types of bonds: 3600 cm−1 (O−H), 1665 cm−1 (C=N) and 945 cm−1 (N−O).
In aqueous solution, aliphatic oximes are 102- to 103-fold more resistant to hydrolysis than analogous hydrazones.
Certain metal salts reduce nitro compounds to oximes.
Oximes can also be obtained from rearrangement of unstable nitroso compounds. Thus react with to give oximes: methyl ethyl ketone with ethyl nitrite, propiophenone with methyl nitrite, and phenacyl chloride with butyl nitrite, all in ethereal hydrochloric acid. Alternatively, sodium nitrite in glacial acetic acid nitrosates ethyl acetoacetate and malononitrile.
A conceptually related reaction is the Japp–Klingemann reaction.
In general, oximes can be changed to the corresponding amide derivatives by treatment with various acids. This reaction is called Beckmann rearrangement. (2025). 9780199270293, Oxford University Press. ISBN 9780199270293 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) concerning the conversion of m-nitrobenzaldoxime to m-nitrophenyldinitromethane using dinitrogen tetroxide was the result of research into Trinitrotoluene analogues: Gentler oxidants give mono-nitro compounds.
In the Neber rearrangement certain oximes are converted to the corresponding alpha-amino ketones.
Oximes can be dehydrated using to yield corresponding .
Certain amidoximes react with benzenesulfonyl chloride to make substituted in the Tiemann rearrangement:
Amidoximes such as polyacrylamidoxime can be used to capture trace amounts of uranium from sea water. In 2017 researchers announced a configuration that absorbed up to nine times as much uranyl as previous fibers without saturating.
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