When primary amines are treated with acid chlorides, we get:

Concept:

• Pure amines are generally colourless, have a fishy smell, and are liquids in nature.
• The chemical reactivity of amines is mainly due to the presence of a lone pair of electrons on the N-atom due to which amines act as nucleophiles or bases.
• A nucleophile is a species that attacks an electron-deficient carbon and a base that attacks an electron-deficient atom.
• In aromatic amines, the lone pair of electrons on nitrogen activates the aromatic ring towards an electrophilic substitution reaction.
• Some reactions of amines are due to basic nature, alkylation, acylation, benzoylation, reaction with Hinsberg reagent, carbylamine reaction, etc.

Explanation:

Acylation of amines:

• Primary and secondary amines containing replaceable hydrogen atoms react with acid chlorides and acid anhydrides to form substituted amides.

• Tertiary amines do not contain replaceable hydrogen atoms so these do not undergo reaction with an acid chloride or acid anhydride.
• The acid generated during the reaction can protonate the amine and destroy its nucleophilic character. Hence, a base is used.
• Unlike in the case of the alkylation reaction of amines, the amide formed does not react further with organic halide or acid anhydride because the amide is non-basic and poor nucleophile due to the electron-withdrawing effect of the -CO-R group.
• Acyl chlorides are stronger acylating agents than anhydrides and esters.

Hence, when primary amines are treated with acid chlorides we get amides.

Additional Information

• Carboxylic acids do not form amides with amines. they only form salts.
• In the case of acylation, the presence of an H atom on Nitrogen is necessary in addition to the nucleophilic character of amines.