The reaction of amines with mineral acids to form ammonium salts shows that these are basic in nature. Amines have an unshared pair of electrons on the nitrogen atoms due to which they behave as Lewis bases. The basicity of amines is related to their structure. The basic character of an amine depends upon the ease of formation of a cation by accepting a proton from the acid. The more stable the cation is relative to the amine, the more basic the amine.
Structure of ammonium salt when ethylamine reacts with one mole of HCl?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → C2H5–NH3+ Cl−
Amines are bases because of the unshared electron pair on nitrogen. With a mineral acid the nitrogen accepts a proton and an ammonium salt is formed. Ethylamine is a primary amine with two hydrogens on nitrogen; one mole of HCl adds one proton:
\( \ce{C2H5-NH2 + HCl -> C2H5-NH3^+Cl^-} \)
The salt is ethylammonium chloride, with three hydrogens on nitrogen and the same single ethyl group.
Why the other options are incorrect
Option (2) (C2H5)2–NH2+ Cl− — Incorrect. Diethylammonium chloride, formed from the secondary amine diethylamine; adding a proton cannot add an ethyl group.
Option (3) (C2H5)3–NH+ Cl− — Incorrect. Triethylammonium chloride, formed from the tertiary amine triethylamine.
Option (4) (C2H5)4–N+ Cl− — Incorrect. A quaternary ammonium salt; it is formed by alkylation with ethyl chloride, not by reaction with an acid.
NCERT (2026-27 edition):
Basic Character of Amines – “Amines, being basic in nature, react with acids to form salts. Amine salts on treatment with a base like NaOH, regenerate the parent amine. Amine salts are soluble in water but insoluble in organic solvents like ether. This reaction is the basis for the separation of amines from the non basic organic compounds insoluble in water.”