HYDROLYSIS OF NITRILE

 

The hydrolysis of nitriles, which are organic molecules containing a cyano group, leads to carboxylic acid formation. These hydrolysis reactions can take place in either acidic or basic solutions.

 

The mechanism for these reactions involves the formation of an amide followed by hydrolysis of the amide to the acid. The mechanism follows these steps:

1.      The nitrogen atom of the nitrile group is protonated.

 

2..      The carbocation generated in Step 1 attracts a water molecule

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3.      The oxonium ion loses a proton to the nitrogen atom, forming an enol.

 

4.      The enol tautomerizes to the more stable keto form.

 

5.      The amide is protonated by the acid, forming a carbocation.

 

6.      A water molecule is attracted to the carbocation.

 

7.      The oxonium ion loses a proton.

 

8.      The amine group is protonated.

 

9.      An electron pair on one of the oxygens displaces the ammonium group from the molecule.

http://www.cliffsnotes.com/study_guide/Preparation-of-Carboxylic-Acids.topicArticleId-23297,articleId-23284.html

Hydrolysis of nitriles with aqueous acid to give carboxylic acids

Description: Addition of water and acid to a nitrile leads to formation of a carboxylic acid.
Notes:

• This reaction is referred to as “acidic hydrolysis”.
• The reaction is generally used with water as solvent, so an excess of water is present. The acid used is often written as “H3O(+)”

Examples:
 


Notes: Note that example 4 is a cyanohydrin, so this produces an “alpha hydroxy carboxylic acid”

Mechanism:

Protonation of the nitrile nitrogen by acid (Step 1, arrows A and B) makes the nitrile carbon a better electrophile. Attack at the carbon by water (Step 2, arrows C and D) followed by proton transfer (Step 3, arrows E and F) gives a species that is in resonance with a protonated amide (arrows G and H). Addition of water to the protonated amide (Step 4, arrows I and J) followed by proton transfer (Step 5, arrows K and L) result in formation of NH3(+) which is an excellent leaving group. Expulsion of NH3 through 1,2-addition (Step 6, arrows M and N) followed by deprotonation (Step 7, arrows O and P) give the carboxylic acid.

 

 http://masterorganicchemistry.com/reaction-guide/hydrolysis-of-nitriles-with-aqueous-acid-to-give-carboxylic-acids/

Nitrile Hydrolysis in Basic Conditions

 

http://chemistry.boisestate.edu/people/richardbanks/organic/nitrilehydrolysisbasicReview.htm

Aliphatic nitriles are prepared by treatment of alkyl halides with sodium cyanide in a solvent that will dissolve both reactants. In dimethyl sulfoxide (DMSO), reaction occurs rapidly and exothermically at room temperature. The resulting nitrile is then hydrolysed to the acid by boiling with aqueous alkali or acid.