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.