This article will be permanently flagged as inappropriate and made unaccessible to everyone. Are you certain this article is inappropriate? Excessive Violence Sexual Content Political / Social
Email Address:
Article Id: WHEBN0000314960 Reproduction Date:
An oxime is a Amidoximes are oximes of amides with general structure RC(=NOH)(NRR').
Oximes are usually generated by the reaction of hydroxylamine and aldehydes or ketones. The term oxime dates back to the 19th century, a portmanteau of the words oxygen and imine.[1]
Oximes exist as two geometric stereoisomers: a syn isomer and an anti isomer. Aldoximes, except for aromatic aldoximes, which exist only as anti isomers, and ketoximes can be separated almost completely and obtained as a syn isomer and an anti isomer.
Oximes have three characteristic bands in the infrared spectrum, at wavenumbers 3600 (O-H), 1665 (C=N) and 945 (N-O).[2]
In aqueous solution, aliphatic oximes are 102- to 103-fold more resistant to hydrolysis than analogous hydrazones.[3]
Oximes can be synthesized by condensation of an aldehyde or a ketone with hydroxylamine. The condensation of aldehydes with hydroxylamine gives aldoxime, and ketoxime is produced from ketones and hydroxylamine. In general, oximes exist as colorless crystals and are poorly soluble in water. Therefore, oximes can be used for the identification of ketone or aldehyde.
Oximes can also be obtained from reaction of nitrites such as isoamyl nitrite with compounds containing an acidic hydrogen atom. Examples are the reaction of ethyl acetoacetate and sodium nitrite in acetic acid,[4][5] the reaction of methyl ethyl ketone with ethyl nitrite in hydrochloric acid.[6] and a similar reaction with propiophenone,[7] the reaction of phenacyl chloride,[8] the reaction of malononitrile with sodium nitrite in acetic acid[9]
A conceptually related reaction is the Japp–Klingemann reaction.
The sodium metal,[10] sodium amalgam, hydrogenation, or reaction with hydride reagents produces amines.[11] Typically the 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.[12]
In general, oximes can be changed to the corresponding amide derivatives by treatment with various acids. This reaction is called Beckmann rearrangement. 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). And an amine by hoffman degradation of the amide in the presence of alkali hypoclorites at 80 degrees Celsius, the degradation is itself prone to side reactions, namely the formation of biurets or cyanate polymers., To avoid this side-reaction, strict temperature control is necessary; the reaction must be conducted at sufficient temperature to isomerise the cyanate to the isocyante. Also, good solvation is also crucial to be successful. Beckmann rearrangement is used for the industrial synthesis of caprolactam (see applications below).
The Ponzio reaction (1906)[13] concerning the conversion of m-nitrobenzaldoxime to m-nitrophenyldinitromethane with dinitrogen tetroxide was the result of research into TNT-like high explosives:[14]
In the Neber rearrangement certain oximes are converted to the corresponding alpha-amino ketones.
Certain amidoximes react with benzenesulfonyl chloride to substituted ureas in the Tiemann rearrangement[15][16]
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 billion kilograms 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:
Nitrogen, Alcohol, Functional group, Electron, Carbonyl
Iron, Oxime, Chemical nomenclature, ChEBI, ChemSpider
Peripheral nervous system, Spinal cord, Synapse, Central nervous system, Meninges
Paracelsus, Venom, Poison, Biology, Chemistry
Ethanol, Hydrogen, Glucose, Antimony, Sodium
Amine, Rhodium, International Union of Pure and Applied Chemistry, Compendium of Chemical Terminology, Oxime
Amide, Aniline, Imine, Alcohol, Acid
Zinc, Oxime, Chemical reaction, Pyrrole, Amino
PubChem, ChemSpider, Chemical formula, Oxime, Lamiaceae
Chemical class, Alcohol, Imine, /anic Peroxide, Amine