Amides

· Amides contain the amide functional group: RCONH₂, RCONHR, or RCONR₂.
· The key bond pattern is C(=O)–N: a carbonyl group directly bonded to nitrogen.
· Primary amide: RCONH₂; secondary amide: RCONHR; tertiary amide: RCONR₂.
· Example: propanamide = CH₃CH₂CONH₂.
· In exam questions, identify the amide linkage by spotting –CONH– or –CONH₂.

This diagram shows delocalisation of the nitrogen lone pair into the carbonyl group. This is the key reason amides have reduced basicity compared with amines. Source

Production of Amides

· Amides are produced from acyl chlorides at room temperature.
· Acyl chloride + ammonia → primary amide.
· General equation: RCOCl + 2NH₃ → RCONH₂ + NH₄Cl.
· Example: CH₃COCl + 2NH₃ → CH₃CONH₂ + NH₄Cl.
· Acyl chloride + primary amine → substituted amide.
· General equation: RCOCl + 2R′NH₂ → RCONHR′ + R′NH₃Cl.
· The reaction is a condensation reaction because HCl is removed/neutralised during amide formation.
· Exam tip: always include room temperature for amide formation from acyl chlorides.

This image shows how an acyl chloride reacts with ammonia to form an amide. It also helps show why ammonium chloride is formed as a by-product. Source

Hydrolysis of Amides

· Hydrolysis = breaking the amide bond using water under acidic or alkaline conditions.
· Acid hydrolysis: amide is heated with aqueous acid.
· Primary amide general equation: RCONH₂ + H₂O + H⁺ → RCOOH + NH₄⁺.
· Product of acid hydrolysis: carboxylic acid + ammonium ion / ammonium salt.
· Alkaline hydrolysis: amide is heated with aqueous alkali, e.g. NaOH(aq).
· Primary amide general equation: RCONH₂ + OH⁻ → RCOO⁻ + NH₃.
· With NaOH: RCONH₂ + NaOH → RCOONa + NH₃.
· Product of alkaline hydrolysis: carboxylate salt + ammonia or amine.
· Exam tip: acid hydrolysis gives RCOOH, but alkaline hydrolysis gives RCOO⁻ / salt.

Reduction of Amides

· Amides are reduced by LiAlH₄.
· Reagent: LiAlH₄.
· Key change: the C=O group is reduced and converted into –CH₂–.
· General equation pattern: RCONH₂ → RCH₂NH₂.
· Primary amide → primary amine.
· Secondary amide → secondary amine.
· Tertiary amide → tertiary amine.
· Exam tip: the carbon skeleton is retained; the carbonyl carbon remains in the product as CH₂.

This reaction scheme shows that LiAlH₄ reduces amides to amines. The important exam point is that the amide carbonyl group becomes CH₂. Source

Why Amides Are Much Weaker Bases Than Amines

· Amines are basic because the nitrogen lone pair is available to accept H⁺.
· In amides, the nitrogen lone pair is delocalised into the carbonyl group.
· This delocalisation gives the C–N bond partial double-bond character.
· Because the lone pair is less available, amides are much weaker bases than amines.
· The C=O group withdraws electron density from nitrogen, further reducing basicity.
· Exam phrase: “The lone pair on nitrogen is delocalised into the carbonyl group, so it is less available to accept a proton.”

This diagram directly compares the available lone pair in an amine with the delocalised lone pair in an amide. It supports the exam explanation for why amides are much weaker bases than amines. Source

Exam Reaction Summary

· RCOCl + 2NH₃ → RCONH₂ + NH₄Cl = making a primary amide.
· RCOCl + 2R′NH₂ → RCONHR′ + R′NH₃Cl = making a substituted amide.
· RCONH₂ + H₂O + H⁺ → RCOOH + NH₄⁺ = acid hydrolysis.
· RCONH₂ + OH⁻ → RCOO⁻ + NH₃ = alkaline hydrolysis.
· RCONH₂ + LiAlH₄ → RCH₂NH₂ = reduction to an amine.