Q.Identify A: aniline + benzaldehyde gives A.

ALKYLATION: successive reaction with R-X climbs 1 to 2 to 3 degree amine to quaternary ammonium salt. ACYLATION: primary/secondary amines + acetyl chloride or acetic anhydride (pyridine present) give an N-alkyl acetamide; aniline + benzoyl chloride/NaOH giving N-phenylbenzamide is specifically the SCHOTTEN-BAUMANN REACTION. REACTION WITH NITROUS ACID (NaNO2 + HCl, in situ) distinguishes all three amine classes AND aliphatic from aromatic: primary ALIPHATIC amines give an unstable alkyl diazonium salt that instantly loses N2 to the alcohol; primary AROMATIC amines at 273-278 K give a diazonium salt that is reasonably stable short-term (this specific step is DIAZOTISATION, feeding the next unit's diazonium-salt chemistry); SECONDARY amines give a yellow, water-insoluble N-nitrosoamine oil (LIEBERMANN'S NITROSO TEST); TERTIARY aliphatic amines give a s …