Q.Complete the following reaction: an aromatic ketone/aldehyde + benzylamine (drawn as a ring-CH2-NH2 group), in the presence of a trace of H+.

Step 1. The reactants are a carbonyl compound (an aromatic aldehyde or ketone, R2C=O) and benzylamine (C6H5-CH2-NH2, a primary amine on a benzylic carbon), with a trace of acid (H+) present as catalyst.

Step 2. The trace acid first protonates the carbonyl oxygen, making the carbonyl carbon MORE electrophilic and speeding the amine nitrogen's nucleophilic addition to it, forming the tetrahedral hemiaminal intermediate.

Step 3. The same acid catalyst then protonates the hemiaminal's -OH, converting it into a good leaving group (water), which departs to form the C=N double bond -- completing imine formation. …

Recognise the trace-acid condition as a catalytic hint for imine (Schiff's base) formation -- the acid speeds both the nucleophilic addition step and the dehydration …

• Treating the 'trace H+' as though it must be a stoichiometric reagent that gets incorporated into the product -- it is a catalyst, protonating and deprotonating at different m …