von Braun amide degradation
The von Braun amide degradation is the chemical reaction of a monosubstituted amide with phosphorus pentachloride or thionyl chloride to give a nitrile and an organohalide.[1] It is named after Julius Jacob von Braun, who first reported the reaction.[2][3]
![The von Braun amide degradation](https://upload.wikimedia.org/wikipedia/commons/thumb/c/c1/Von_Braun_Amide_Degradation_Scheme.png/400px-Von_Braun_Amide_Degradation_Scheme.png)
Reaction mechanism
The secondary amide 1 reacts via its enolized form with phosphorus pentachloride to form the oxonium ion 2. This produces a chloride ion which deprotonates the oxonium ion to form and imine 3 and hydrogen chloride. These then react with one another to form an amine, with loss of the phosphorus chloride residue. The β-chloroimine 4 is unstable and undergoes internal elimination to a form a nitrilium cation 5 which is cleaved by attack by chloride to form a nitrile 6a and a haloalkane 6b.
![](https://upload.wikimedia.org/wikipedia/commons/thumb/8/8f/Von_Braun_Degradation_Reaktionsmechanismus_Teil_1_V4.svg/600px-Von_Braun_Degradation_Reaktionsmechanismus_Teil_1_V4.svg.png)
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