Comprehension:
Amines are derivatives of ammonia obtained by replacement of one, two or all the three hydrogen atoms by alkyl and / or aryl groups. Nitrogen atom of amines like ammonia is trivalent and carries an unshared pair of electrons. Orbitals of nitrogen overlap with orbitals of hydrogen or carbon depending upon the composition of the amines. The fourth orbital of nitrogen in all amines contains an unshared pair of electrons. Due to the presence of unshared pair of electrons, the angle C-N-E (where E is C or H) is less than tetrahedral angle 109.5°. Amines are classified as primary (1°), secondary (2°) and tertiary (3°) amines. All amines are basic in nature and basicity differs between primary amines, secondary amines and tertiary amines. In aryl amines, –NH2 group is directly attached to the benzene ring. C6H5NH2 is simplest example of arylamine. Lower aliphatic amines are soluble in water because they can form hydrogen bonds with water molecules.
N-Methylbenzamide is formed when methanamine reacts with
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → C6H5COCl
Primary and secondary amines react with acid chlorides, anhydrides and esters by nucleophilic substitution: the hydrogen of the –\( \ce{NH2} \) or >N–H group is replaced by an acyl group and an amide is formed. This is acylation; with benzoyl chloride it is called benzoylation. It is carried out in the presence of a base, such as pyridine, which removes the HCl formed.
N-Methylbenzamide is \( \ce{C6H5-CO-NH-CH3} \): a benzoyl group (\( \ce{C6H5CO} \)–) on the nitrogen of methanamine. So methanamine must react with benzoyl chloride.
So the reagent is C6H5COCl.
Why the other options are incorrect
Option (2) C6H5NH2 — Incorrect. Aniline is itself an amine and has no acyl group to transfer, so no amide can form.
Option (3) C6H5COOH — Incorrect. Benzoic acid only forms a salt with the basic amine (\( \ce{CH3NH3^{+}} \) \( \ce{C6H5COO^{-}} \)); the amide forms only on strong heating, not by the usual acylation route.
Option (4) C6H5Cl — Incorrect. Chlorobenzene has no carbonyl group, and aryl halides are very unreactive towards nucleophilic substitution, so no benzamide can form.
NCERT (2026-27 edition):
Acylation – …
