Chemistry · Amines · NEET
At room temperature you get a SALT (ammonium carboxylate), not an amide. The amine is a base, the carboxylic acid is an acid, so the fast step is simple proton transfer: the acid's O-H proton jumps to the amine nitrogen. Example: CH3COOH + CH3NH2 gives CH3COO- +NH3CH3. To get the amide (CH3CONHCH3 + H2O) you must HEAT this salt strongly. NEET wording clue: 'room temperature' or 'cold' means salt; 'on heating / distillation' means amide.
Proton transfer (acid-base) is very fast and needs no energy, so it happens first and dominates in the cold. Making an amide needs the amine nitrogen to attack the acid carbon and then lose a water molecule — this is slow and needs energy (heat) to push out water. So in the cold, only the easy salt forms.
It is an ammonium carboxylate. The carboxylic acid loses H+ to become a carboxylate anion (RCOO-), and the amine gains H+ to become a substituted ammonium cation (R'NH3+). Written as RCOO- R'NH3+. For example, ethanoic acid + methanamine gives ammonium ethanoate type salt: CH3COO- CH3NH3+.
It is the same idea — an acid-base reaction. With HCl the amine forms an ammonium chloride salt (RNH3+ Cl-). With a carboxylic acid it forms an ammonium carboxylate salt (RNH3+ RCOO-). Both prove the amine is basic. The carboxylate salt is special because heating it can go on to form an amide, which the chloride salt cannot.
Yes. Amines have a lone pair on nitrogen, so they act as a base and accept a proton from the acid. The fact that they neutralise carboxylic acids (and mineral acids) to give salts is direct proof of their basic (Lewis base) nature — a common NEET one-liner.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
An ammonium carboxylate salt at room temperature, for example CH3COO- CH3NH3+. On strong heating this salt loses water and becomes an amide.
The salt formation is a fast, reversible acid-base equilibrium. Adding a strong base can free the amine again, and heating drives the salt forward to the amide by removing water.
Primary, secondary and tertiary amines all act as bases and form salts with carboxylic acids. But only primary and secondary amines (which still have an N-H) can go on to form an amide on heating; tertiary amines have no N-H, so they stop at the salt.
It shows amines are basic, and the water-soluble salt lets us separate amines from non-basic organic compounds. On heating, the same salt route is a way to make amides.
NEET more often tests basicity of amines, diazonium reactions, Hinsberg and carbylamine tests. This specific salt-vs-amide idea is usually tested as a trap inside those broader questions, so know it as a concept even if a standalone PYQ is rare.
