Rosenmund–von Braun reaction

Rosenmund–von Braun Reaction

The Rosenmund–von Braun reaction is a notable chemical reaction that involves the synthesis of aryl nitriles from aryl halides. This transformation is facilitated by the presence of a copper(I) catalyst and is conducted in the presence of an alkali metal cyanide. The reaction is named after the chemists Karl Wilhelm Rosenmund and Bernhard von Braun who independently developed this method in the early 20th century.

Reaction Mechanism

The mechanism of the Rosenmund–von Braun reaction begins with the oxidative addition of the aryl halide to the copper(I) catalyst, forming an aryl copper(III) halide complex. This complex then reacts with a cyanide ion, replacing the halide and forming an aryl copper(III) cyanide. Finally, reductive elimination releases the aryl nitrile product and regenerates the copper(I) catalyst.

Applications

The Rosenmund–von Braun reaction is particularly useful in organic synthesis for the preparation of aryl nitriles, which are valuable intermediates in the synthesis of amides, amines, and carboxylic acids. This reaction is advantageous due to its relatively mild conditions and the availability of starting materials.

Limitations

Despite its utility, the Rosenmund–von Braun reaction has some limitations. The reaction conditions can sometimes lead to the hydrolysis of the nitrile product to the corresponding carboxylic acid, especially in the presence of moisture. Additionally, the reaction may exhibit poor selectivity with certain substrates, and the use of toxic cyanide salts requires careful handling and disposal.

Variants

Several modifications and improvements to the original Rosenmund–von Braun reaction have been developed to overcome its limitations. These include the use of different copper catalysts, ligands to improve selectivity, and alternative cyanide sources to mitigate toxicity concerns.

See Also

• Copper(I) cyanide
• Aryl halide
• Nitrile
• Organic synthesis