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The von Braun amide degradation is the
chemical reaction
A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the pos ...
of a monosubstituted amide
In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a compound with the general formula , where R, R', and R″ represent organic groups or hydrogen atoms. The amide group is called a peptide bond when it is ...
with phosphorus pentachloride
Phosphorus pentachloride is the chemical compound with the formula PCl5. It is one of the most important phosphorus chlorides, others being PCl3 and POCl3. PCl5 finds use as a chlorinating reagent. It is a colourless, water-sensitive and moist ...
or thionyl chloride to give a nitrile
In organic chemistry, a nitrile is any organic compound that has a functional group. The prefix ''cyano-'' is used interchangeably with the term ''nitrile'' in industrial literature. Nitriles are found in many useful compounds, including met ...
and an organohalide
In chemistry, a halide (rarely halogenide) is a binary chemical compound, of which one part is a halogen atom and the other part is an element or radical that is less electronegative (or more electropositive) than the halogen, to make a fluor ...
. It is named after Julius Jacob von Braun, who first reported the reaction.
Reaction mechanism
The secondary amide 1 reacts via its enolized form with phosphorus pentachloride to form theoxonium ion
In chemistry, an oxonium ion is any cation containing an oxygen atom that has three bonds and 1+ formal charge. The simplest oxonium ion is the hydronium ion ().
Alkyloxonium
Hydronium is one of a series of oxonium ions with the formula R''n''H ...
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.
See also
* von Braun reaction *Julius von Braun
The gens Julia (''gēns Iūlia'', ) was one of the most prominent patrician families in ancient Rome. Members of the gens attained the highest dignities of the state in the earliest times of the Republic. The first of the family to obtain the ...
*Rosenmund–von Braun reaction
The Rosenmund–von Braun synthesis is an organic reaction in which an aryl halide reacts with cuprous cyanide to yield an aryl nitrile.
:
The reaction was named after Karl Wilhelm Rosenmund who together with his Ph.D. student Erich Struck disc ...
References
{{Reflist Elimination reactions Degradation reactions Name reactions