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.
- 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(+)”
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.