How can I convert the carboxylic acid functional group into a nitrile?


closed as unclear what you're asking by jerepierre, Jon Custer, airhuff, Todd Minehardt, Buttonwood Jun 10 '17 at 16:20

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    $\begingroup$ Butanenitrile has 4 carbons not 5, and if you meant pentanenitrile, why are you trying to remove a carbon? Surely going from 4 to 5 is adding a carbon. $\endgroup$ – orthocresol Jun 8 '17 at 21:04
  • $\begingroup$ it has been edited, could you answer this question? $\endgroup$ – user43537 Jun 8 '17 at 21:50
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    $\begingroup$ Convert to amide then dehydrate to nitrile, should work $\endgroup$ – orthocresol Jun 8 '17 at 21:57
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    $\begingroup$ That's not the formula for butanenitrile. It's butylamine... Which one do you want? $\endgroup$ – Zhe Jun 8 '17 at 22:21

The direct conversion of a carboxylic acid to a nitrile is not a well defined reaction, although examples do exist, the reaction is not general to a wide range of carboxylic acids.

By far the most common method is to convert the carboxylic acid into the primary amide, followed by some method of dehydration. Strongly acidic reagents such as $\ce{P2O5, POCl3, SOCl2, TiCl4, NaBH4}$ have all been used to achieve this, however milder methods such as $\ce{(COCl)2}$ or cyanuric chloride are also common, along with more modern catalytic methods (Matthias Beller has a very nice iron catalysed reaction).

  • $\begingroup$ A method that I've seen used extensively is to make the t-butyl amide and dehydrate that with PCl5 $\endgroup$ – Waylander Jun 9 '17 at 8:35

Carboxylic acid can be converted to nitriles using various methods:

  1. Direct Preparation of Nitriles from Carboxylic Acids in Continuous Flow

A continuous-flow protocol for the preparation of organic nitriles from carboxylic acids has been developed. The method is based on the acid–nitrile exchange reaction with acetonitrile, used as the solvent, and takes place without any catalyst or additives under the high-temperature/high-pressure conditions employed. At 350 °C and 65 bar, where acetonitrile is in its supercritical state, the transformation of benzoic acid to benzonitrile requires 25 min. The protocol has been tested for a variety of nitriles, including aromatic and aliphatic substrates.

  1. Preparation of nitriles from carboxylic acids: A new, synthetically useful example of the Smiles rearrangement

Reaction of 2,4-dinitrobenzenesulfonamide with acyl chlorides in the presence of excess triethylamine produces the corresponding nitrile in good to fair yields. Mechanistic studies indicate that the reaction proceeds via a Smiles rearrangement of the initially formed N-(2,4-dinitrobenzenesulfonyl)amide to form the nitrile, 2,4-dinitrophenol and sulfur dioxide.

The reaction of acyl chlorides with 2,4-dinitobenzenesulfonamide in the presence of TEA gives the corresponding nitrile, 2,4-dinitrophenol and sulfur dioxide. enter image description here

  1. Letts nitrile synthesis(for making aromatic nitrile)

The Letts nitrile synthesis is a chemical reaction of aromaticcarboxylic acids with metal thiocyanates to form nitriles. The reaction includes the loss of carbon dioxide and potassium hydrosulfide. The polar basic substitution reaction was discovered in 1872 by Edmund A. Letts.

enter image description here


Carboxylic acid is first converted into mixed sulfonic anhydride using methanesulfonyl chloride(MSC) in dry pyridine ar 0℃. This anhydride is treated with ammonia to form an intermediate which on dehydrating gives amide. The amide is converted to nitrile using MSC.

enter image description here


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