MECHANISM OF THE ACID CATALYSED HYDROLYSIS OF AMIDES

Step 1: An acid/base reaction. Since we only have a weak nucleophile and apoor electrophile we need to activate the amide. Protonation of the amidecarbonyl makes it more electrophilic.
Step 2: The water O functions as the nucleophile attacking the electrophilicCin the C=O, with the electrons moving towards the oxonium ion, creatingthe tetrahedral intermediate.
Step 3: An acid/base reaction. Deprotonate the oxygen that came from the watermolecule to neutralise the charge.
Step 4: An acid/base reaction. Need to make the -NH2leave, but need to convert it into a good leaving group first byprotonation.
Step 5: Use the electrons of an adjacent oxygen to help "push out" the leavinggroup, a neutral ammonia molecule.
Step 6: An acid/base reaction. Deprotonation of the oxonium ion reveals thecarbonyl in the carboxylic acid product and regenerates the acid catalyst.

REACTION OF RMgX WITH AN NITRILE

Step 1: The nucleophilic C in the organometallic reagent adds to the electrophilic C in the polar nitrile group. Electrons from the CºN move to the electronegative N creating an intermediate imine salt complex.
Step 2: An acid/base reaction. On addition of aqueous acid, the intermediate salt protonates giving the imine.
Step 3: An acid/base reaction. Imines undergo nucleophilic addition, but require activation by protonation (i.e. acid catalysis)
Step 4: Now the nucleophilic O of a water molecule attacks the electrophilic C with the p bond breaking to neutralize the change on the N.
Step 5: An acid/base reaction. Deprotonate the O from the water molecule to neutralize the positive charge.
Step 6: An acid/base reaction. Before the N system leaves, it needs to be made into a better leaving group by protonation.
Step 7: Use the electrons on the O in order to push out the N leaving group, a neutral molecule of ammonia.
Step 8: An acid/base reaction. Deprotonation reveals the carbonyl group of the ketone product.

MECHANISM OF THE ACID catalyzed HYDROLYSIS OF NITRILES

Step 1: An acid/base reaction. Since we only have a weak nucleophile so activate the nitrile, protonation makes it more electrophilic.
Step 2: The water O functions as the nucleophile attacking the electrophilic C in the CºN, with the electrons moving towards the positive center.
Step 3: An acid/base reaction. Deprotonate the oxygen that came from the water molecule. The remaining task is a tautomerization at N and O centers.
Step 4: An acid/base reaction. Protonate the N gives us the -NH2 we need....
Step 5: Use the electrons of an adjacent O to neutralise the positive at the N and form the p bond in the C=O.
Step 6: An acid/base reaction. Deprotonation of the oxonium ion reveals the carbonyl in the amide intermediate....halfway to the acid.....

HYDROLYSING NITRILES

The hydrolysis of nitriles

Introduction

When nitriles are hydrolysed you can think of them reacting with water in two stages - first to produce an amide, and then the ammonium salt of a carboxylic acid.

For example, ethanenitrile would end up as ammonium ethanoate going via ethanamide.

In practice, the reaction between nitriles and water would be so slow as to be completely negligible. The nitrile is instead heated with either a dilute acid such as dilute hydrochloric acid, or with an alkali such as sodium hydroxide solution.

The end result is similar in all the cases, but the exact nature of the final product varies depending on the conditions you use for the reaction.

Acidic hydrolysis of nitriles

The nitrile is heated under reflux with dilute hydrochloric acid. Instead of getting an ammonium salt as you would do if the reaction only involved water, you produce the free carboxylic acid.

For example, with ethanenitrile and hydrochloric acid you would get ethanoic acid and ammonium chloride.

Why is the free acid formed rather than the ammonium salt? The ethanoate ions in the ammonium ethanoate react with hydrogen ions from the hydrochloric acid to produce ethanoic acid. Ethanoic acid is only a weak acid and so once it has got the hydrogen ion, it tends to hang on to it.

Alkaline hydrolysis of nitriles

The nitrile is heated under reflux with sodium hydroxide solution. This time, instead of getting an ammonium salt as you would do if the reaction only involved water, you get the sodium salt. Ammonia gas is given off as well.

For example, with ethanenitrile and sodium hydroxide solution you would get sodium ethanoate and ammonia.

The ammonia is formed from reaction between ammonium ions and hydroxide ions.

If you wanted the free carboxylic acid in this case, you would have to acidify the final solution with a strong acid such as dilute hydrochloric acid or dilute sulphuric acid. The ethanoate ion in the sodium ethanoate will react with hydrogen ions as mentioned above.

Hydrolysis of carboxylic acid derivatives (13)

hydrolysis of nitryle part 4(last)....

Hydrolysis of carboxylic acid derivatives (12)

Hydrolysis of nitryle part 3...

Hydrolysis of carboxylic acid derivatives (11)

hydrolysis of niryle part 2...