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The Hofmann rearrangement (Hofmann degradation) is the organic reaction of a primary amide to a primary amine with one less carbon atom. [1] [2] [3] The reaction involves oxidation of the nitrogen followed by rearrangement of the carbonyl and nitrogen to give an isocyanate intermediate.
In this context, the reaction is also known as Saytzeff's isocyanide test. [2] In this reaction, the analyte is heated with alcoholic potassium hydroxide and chloroform. If a primary amine is present, the isocyanide (carbylamine) is formed, as indicated by a foul odour. The carbylamine test does not give a positive reaction with secondary and ...
In the carbylamine reaction (also known as the Hofmann isocyanide synthesis) alkali base reacts with chloroform to produce dichlorocarbene. The carbene then converts primary amines to isocyanides. Illustrative is the synthesis of tert -butyl isocyanide from tert -butylamine in the presence of catalytic amount of the phase transfer catalyst ...
Notice that some C-N-C angles strongly deviate from 180°, a characteristic of low-valent isocyanide complexes. [8] Because of their low steric profile and high basicity, isocyanide ligands often install easily, e.g. by treating metal halides with the isocyanide. Many metal cyanides can be N-alkylated to give isocyanide complexes. [9]
This requires mixing the compounds in a reaction vessel, such as a chemical reactor or a simple round-bottom flask. Many reactions require some form of processing ("work-up") or purification procedure to isolate the final product. [1] The amount produced by chemical synthesis is known as the reaction yield.
Reaction mechanism for the Bucherer–Bergs reaction. Following condensation of the carbonyl with the ammonium, the formed imine is attacked by the isocyanide to form the aminonitrile. Nucleophilic addition of aminonitrile to CO 2 leads to cyano-carbamic acid, which undergoes an intramolecular ring closing to 5-imino-oxazolidin-2-one.
The Barton–Zard reaction is a route to pyrrole derivatives via the reaction of a nitroalkene with an α-isocyanide under basic conditions. [1] It is named after Derek Barton and Samir Zard who first reported it in 1985.
The Passerini reaction can also exhibit enantioselectivity. Addition of tert-butyl isocyanide to a wide variety of aldehydes (aromatic, heteroaromatic, olefinic, acetylenic, aliphatic) is achieved using a catalytic system of tetrachloride and a chiral bisphosphoramide which provides good yield and good enantioselectivities. [19]