Aldoksimien

Aldoximes are a class of organic compounds characterized by the oxime functional group attached to an aldehyde-derived carbon, with the general formula R-CH=NOH. They are the oximes of aldehydes, in contrast to ketoximes derived from ketones, and they can exist as geometric isomers around the C=N bond (E and Z).

They are typically prepared by condensation of aldehydes with hydroxylamine (NH2OH) under basic or mildly acidic conditions, with removal of water. Common methods use hydroxylamine hydrochloride and a base such as sodium acetate in an alcohol solvent.

Aldoximes participate in several useful transformations. In a Beckmann rearrangement, aldoximes convert to primary amides, R-CO-NH2, under acid catalysis. They can also be dehydrated to nitriles, R-CN, using dehydrating agents such as phosphorus oxychloride or thionyl chloride. Catalytic hydrogenation reduces aldoximes to the corresponding primary amines, R-CH2NH2. Other reactions include alkylation or acylation at the oxime nitrogen to give N-substituted oxime derivatives.

Applications and occurrence: Aldoximes are important intermediates in organic synthesis, used to access amides, nitriles, amines, and other functional groups. They are typically prepared from readily available aldehydes and are found in laboratory-scale syntheses rather than as persistent natural products.

Safety: Aldoximes are generally of moderate handling hazard, potentially irritating to skin and eyes. Some oximes or dehydration products (nitriles, amides) can be hazardous; proper ventilation and protective equipment are recommended.