Chemistry · Amines · NEET
In alkylation, the amine reacts with an alkyl halide (R-X) and a plain alkyl group (like -CH3 or -C2H5) joins the nitrogen. The product is still an amine, just a bigger one (primary becomes secondary, then tertiary, then a quaternary ammonium salt). In acylation, the amine reacts with an acyl chloride (RCOCl), an anhydride, or an ester, and an acyl group (R-CO-) joins the nitrogen. The product is now an amide (>N-CO-R), not an amine. So the key difference is: alkylation gives a more-substituted amine, acylation gives an amide.
Acylation means putting an acyl group (R-CO-) onto the nitrogen. A primary or secondary amine attacks the carbonyl carbon of an acid chloride, anhydride or ester by nucleophilic substitution. One N-H hydrogen is replaced by the acyl group. The product is an amide. For example, aniline plus acetyl chloride gives acetanilide (C6H5-NH-COCH3). NCERT calls this reaction acylation.
When an amine reacts with an acyl chloride, HCl is released. This HCl can protonate the basic amine and stop the reaction. So we add a base that is stronger than the amine, like pyridine. Pyridine removes the HCl, so the equilibrium shifts to the right and more amide is formed. That is why NCERT says the reaction is carried out in the presence of pyridine.
Yes. When ammonia or an amine reacts with an alkyl halide, the first product is a more nucleophilic amine, which reacts again with the alkyl halide. So you get a mixture: primary, then secondary, then tertiary amine, and finally a quaternary ammonium salt. To get mainly the primary amine, you take a large excess of ammonia. This is why alkylation (ammonolysis) is not a clean method for one single amine.
Only primary and secondary amines undergo acylation, because they have an N-H hydrogen that the acyl group can replace. A tertiary amine (like triethylamine) has no N-H bond, so it cannot form an amide. This N-H rule is also why the Hinsberg test (a sulphonylation, which is acyl-type) separates the three classes of amines.
Friedel-Crafts alkylation needs a Lewis acid like AlCl3. Aniline has a basic nitrogen lone pair, so AlCl3 attacks the nitrogen and forms a salt (an acid-base complex). This puts a positive charge on nitrogen, which strongly deactivates the ring and also uses up the AlCl3. So aniline does not undergo Friedel-Crafts alkylation. This was directly asked in NEET 2024.
Statement I: Aniline does not undergo Friedel-Crafts alkylation reaction. Statement II: Aniline cannot be prepared through Gabriel synthesis. Choose the correct answer.
The amine that reacts with Hinsberg's reagent to give an alkali-insoluble product is:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Yes. The amine nitrogen (a nucleophile) attacks the electron-poor carbonyl carbon of the acyl chloride, anhydride or ester. The leaving group (like Cl-) departs, and an amide forms. NCERT clearly calls acylation a nucleophilic substitution reaction.
Benzoylation is a special acylation using benzoyl chloride (C6H5COCl). A primary or secondary amine reacts to give a benzamide, for example aniline plus benzoyl chloride gives N-phenylbenzamide (benzanilide). It is carried out under Schotten-Baumann conditions (in the presence of aqueous NaOH).
The -NH2 group activates the benzene ring strongly and can be oxidised or give too much substitution. Acetylating aniline to acetanilide reduces this activating power, so nitration gives mainly the para product cleanly. After nitration the acetyl group is removed by hydrolysis to get back the amine. This shows why acylation is used to control the reactivity of aromatic amines.
It decreases basicity. In the amide product (like acetanilide) the nitrogen lone pair is pulled into the carbonyl group by resonance, so it is less available to accept a proton. That is why an amide is much less basic than the parent amine.
