I have one question. How changes nucleophilic reactions between paradimethylaminobenzaldehyde and benzaldehyde

Answer 1

The difference between para-dimethylaminobenzaldehyde and benzaldehyde towards a nucleophilic reaction (presumably on the aldehyde carbonyl) can be rather large. The p-dimethylamino group is a strong electron-donating group to the aromatic ring and this would reduce the electrophilicity of the carbonyl carbon towards a nucleophilic addition reaction. On the other hand, the carbonyl of unsubstituted benzaldehyde is a rather strong electrophile towards nucleophilic addition reactions.