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The von Braun amide degradation is the
chemical reaction
A chemical reaction is a process that leads to the chemistry, chemical transformation of one set of chemical substances to another. When chemical reactions occur, the atoms are rearranged and the reaction is accompanied by an Gibbs free energy, ...
of a monosubstituted amide
In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a chemical compound, compound with the general formula , where R, R', and R″ represent any group, typically organyl functional group, groups or hydrogen at ...
with phosphorus pentachloride
Phosphorus pentachloride is the chemical compound with the formula . It is one of the most important phosphorus chlorides/oxychlorides, others being and . finds use as a chlorinating reagent. It is a colourless, water-sensitive solid, althoug ...
or thionyl chloride
Thionyl chloride is an inorganic compound with the chemical formula . It is a moderately Volatility (chemistry), volatile, colourless liquid with an unpleasant acrid odour. Thionyl chloride is primarily used as a Halogenation, chlorinating reagen ...
to give a nitrile
In organic chemistry, a nitrile is any organic compound that has a functional group. The name of the compound is composed of a base, which includes the carbon of the , suffixed with "nitrile", so for example is called " propionitrile" (or pr ...
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 fl ...
. 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 chemical bond, 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 fo ...
2. This produces a chloride ion which deprotonates the oxonium ion to form and imine
In organic chemistry, an imine ( or ) is a functional group or organic compound containing a carbon–nitrogen double bond (). The nitrogen atom can be attached to a hydrogen or an organic group (R). The carbon atom has two additional single bon ...
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
A nitrilium ion is a nitrile that has been protonated, CNH, or alkylated, CNR′.
Synthesis
Nitriles are only weakly basic and are poor nucleophiles, but they will attack very reactive electrophiles such as carbocations.
Nitrilium salts ...
cation 5 which is cleaved by attack by chloride to form a nitrile 6a and a haloalkane 6b.
See also
*von Braun reaction
The von Braun reaction is an organic reaction in which a tertiary amine reacts with cyanogen bromide to an organocyanamide.
An example is the reaction of ''N'',''N''-dimethyl-1-naphthylamine:
These days, most chemist have replaced cyanogen b ...
* Julius von Braun
*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
{{Organic reactions Elimination reactions Degradation reactions Name reactions