3.9: Chemistry of Amides- Synthesis and Reactions
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Synthesis of Amides
Direct reaction of a carboxylic acid with an amine does not produce an amide, but a salt.
Therefore, we need to use acyl chlorides or anhydrides as an alternative.
Acid chlorides react with ammonia, 1o amines and 2o amines to form amides
Acid Anhydrides react with ammonia, 1o amines and 2o amines to form amides
Examples
Tertiary amines cannot form amides due to the lack of H atom that can be replaced by the acyl group
Chemical properties of Amides
Hydrolysis under acidic conditions
Taking acetamide (ethanamide) as a typical amide. If acetamide is heated with a dilute acid (such as dilute hydrochloric acid), acetic acid is formed together with ammonium ions. So, if you were using hydrochloric acid, the final solution would contain ammonium chloride and acetic acid.
Hydrolysis under alkaline conditions
Also, if acetamide is heated with sodium hydroxide solution, ammonia gas is given off and you are left with a solution containing sodium acetate.
Peptide hydrolysis
Peptide hydrolysis of proteins is amide hydrolysis. What biologists and biochemists call a peptide link (in proteins, for example) is what chemists call an amide link. Apply either hydrolysis reaction above to the dipeptide below to produce two amino acids. The amines in the products are shown in their protonated form because this hydrolysis reaction was performed under acidic conditions.
Contributors and Attributions
Dr. Dietmar Kennepohl FCIC (Professor of Chemistry, Athabasca University)
Prof. Steven Farmer (Sonoma State University)
Jim Clark (Chemguide.co.uk)