Lesson 6 of 12 · 5 min
Acylation, alkylation and the carbylamine test
NCERT §9.6
The dye works protects aniline before some reactions by turning it into acetanilide. Ravi runs the acetylation and, on a separate bench, a smell test he will never forget.
The lesson in notes
In short
Alkylation: amines react with alkyl halides, as in ammonolysis, moving up to the quaternary salt.
Acylation: any primary or secondary amine, aliphatic or aromatic, swaps an N–H hydrogen for an acyl group when treated with an acid chloride, an anhydride or an ester. The reaction is a nucleophilic substitution and the product is an amide.
Acylation is run with a base stronger than the amine, such as pyridine, which removes the HCl formed and pushes the equilibrium forward.
Examples: ethanamine with ethanoyl chloride gives N-ethylethanamide; aniline with ethanoic anhydride gives N-phenylethanamide (acetanilide).
Benzoylation is acylation with benzoyl chloride, C₆H₅COCl: methanamine gives N-methylbenzamide.
With carboxylic acids at room temperature, amines simply form salts.
Carbylamine reaction (isocyanide test): a primary amine, aliphatic or aromatic, heated with chloroform and ethanolic KOH gives a foul-smelling isocyanide. Secondary and tertiary amines do not react, so this is a test for primary amines.
Equation: R–NH₂ + CHCl₃ + 3KOH → R–NC + 3KCl + 3H₂O (on heating).
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Isocyanide test for primary amines
Land of Chemistry · English · Demo · Open on YouTube