9701 · 34.3
Amides flashcards
Revision flashcards for Cambridge 9701 Amides (syllabus 34.3). Flip, recall, then mark a real past-paper question.
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What is the functional group of a primary amide?
The -CONH₂ group, where a carbonyl group (C=O) is directly attached to an amino group (-NH₂).
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Why is the C-N bond in an amide planar?
Due to delocalisation. The lone pair of electrons on the nitrogen atom is drawn into the pi system of the C=O group, giving the C-N bond partial double bond character. This restricts rotation and forces the atoms in the group (-OCNH-) to lie in the same plane.
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Why are amides neutral, while amines are basic?
In amides, the lone pair on the nitrogen atom is delocalised into the carbonyl group's pi system. This makes the lone pair unavailable to accept a proton (H⁺), so amides are not basic.
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What are the reactants for forming a primary amide from an acyl chloride?
An acyl chloride (RCOCl) and two moles of ammonia (NH₃). One mole acts as a nucleophile, the other as a base.
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Write the general equation for the formation of an N-substituted amide.
RCOCl + 2R'NH₂ → RCONHR' + R'NH₃⁺Cl⁻. An acyl chloride reacts with two equivalents of a primary amine.
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What are the conditions for the hydrolysis of an amide?
Heating under reflux with either a strong acid (e.g., dilute H₂SO₄) or a strong alkali (e.g., aqueous NaOH).
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What are the products of the acid hydrolysis of propanamide?
Propanoic acid (CH₃CH₂COOH) and an ammonium salt (NH₄⁺). The ammonia produced is immediately protonated by the excess acid.
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What are the products of the alkaline hydrolysis of N-methylethanamide?
Sodium ethanoate (CH₃COO⁻Na⁺) and methylamine (CH₃NH₂). The carboxylic acid produced is immediately deprotonated by the excess alkali.
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What is a peptide bond?
A peptide bond is the specific name for the amide link that joins amino acid monomers together to form peptides and proteins.
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What is the difference between a primary, secondary, and tertiary amide?
It depends on the number of alkyl/aryl groups attached to the nitrogen atom. Primary (RCONH₂): no groups. Secondary (RCONHR'): one group. Tertiary (RCONR'₂): two groups.