Amides (Edexcel International A Level Chemistry): Revision Note

Amide Formation

• Amides are organic compounds with an -CONR₂ functional group

• They can be prepared from the condensation reaction between an acyl chloride and ammonia or amine

• In a condensation reaction, two organic molecules join together and in the process eliminate a small molecule

• In this case, the acyl chlorides and ammonia or amine join together to form an amide and eliminate an HCl molecule

Condensation reaction

• The chlorine atom in acyl chlorides is electronegative and draws electron density from the carbonyl carbon

• The carbonyl carbon is therefore electron-deficient and can be attacked by nucleophiles

• The nitrogen atom in ammonia and amines has a lone pair of electrons which can act as a nucleophile and attack the carbonyl carbon

• As a result, the C-Cl bond is broken and an amide is formed

• Whether the product is a substituted amide or not, depends on the nature of the nucleophile

  • Primary and secondary amines will give a substituted amide

  • The reaction of acyl chlorides with ammonia will produce a non-substituted amide

Acyl chlorides undergo condensation reactions with ammonia and amines to form amides

• Note that ammonia is basic and the inorganic product is acidic, so there will be a reaction between the two molecules

NH₃ + HCl → NH₄Cl

• We can therefore write the overall equation for the reaction of propanoyl chloride and ammonia as

CH₃CH₂COCl + 2NH₃ → CH₃CH₂CONH₂ + NH₄Cl