Organic Chemistry III

What Organic Chemistry III covers

Covers benzene and the evidence for its delocalised structure, electrophilic substitution and its mechanisms, phenol, the amines, amides and condensation polymers, amino acids and proteins, and multi-step synthesis with its analysis and purification.

The 10 subtopics

Each one has its own page.

• The structure of benzene and the evidence for itRecall questions on the Kekulé structure and the delocalised model, and on the bond lengths, hydrogenation enthalpies and lack of reactivity that decide between them.Open →
• Electrophilic substitution of benzeneThe reagents, catalysts and products for the bromination and nitration of benzene, Friedel-Crafts alkylation and acylation with aluminium chloride, and how the halogen carrier generates the electrophile.Open →
• Nitration, halogenation, Friedel-Crafts and phenolThe mechanisms of halogenation, nitration and Friedel-Crafts alkylation and acylation of benzene, including how each electrophile forms and each catalyst is regenerated, and why phenol decolourises bromine water to give 2,4,6-tribromophenol without a catalyst.Open →
• Amines: structure and basicityThe structures of primary, secondary and tertiary amines, of amides and of amino acids, how butylamine accepts a proton to give an alkaline solution, and the reactions of primary amines with acids and with acyl chlorides.Open →
• Reactions of amines and preparing themAmines reacting with halogenoalkanes to give a mixture of products, amines as ligands with copper(II) ions, why aliphatic amines are stronger and aromatic amines weaker bases than ammonia, and preparing amines from halogenoalkanes, nitriles and aromatic nitro-compounds.Open →
• Amides and condensation polymersAcyl chlorides forming amides, condensation polymerisation to polyesters from dicarboxylic acids and diols and to polyamides from dicarboxylic acids and diamines, their ester and amide linkages, and the water eliminated as each linkage forms.Open →
• Amino acids, zwitterions and proteinsPeptide bonds and condensation to polypeptides, 2-amino acids acting as acids and bases, zwitterions, why most amino acids are optically active but glycine is not, and hydrolysing a protein and separating its amino acids by chromatography.Open →
• Empirical and molecular formulae from analytical dataEmpirical formulae from combustion analysis and from percentage composition, the molecular formula from the relative molecular mass, and what functional group tests, infrared spectra, mass spectra and NMR each contribute to identifying an unknown compound.Open →
• Grignard reagents and multi-step synthesisRecall questions on preparing and using a Grignard reagent, on how it lengthens a carbon chain, and on planning a route between two functional groups.Open →
• Purification techniques and the aspirin preparationReflux, washing, solvent extraction, recrystallisation and drying, simple and steam distillation, judging purity from melting and boiling temperatures, and preparing aspirin by acetylating 2-hydroxybenzoic acid with ethanoic anhydride, then purifying it and checking its purity.Open →

What you need to know

Answer each one before you reveal it.

Take Organic Chemistry III further

The same content, four other ways.

Commonly confused

Pairs that lose marks when they are blurred together.

• Aliphatic compound vs Aromatic compound

  Aliphatic compound: carbon compound without an aromatic ring. Aromatic compound: compound containing a stable delocalised ring system.

• Reflux vs Distillation

  Reflux: continuous boiling and condensation without volatile loss. Distillation: separation by vaporisation, condensation and collection.

Questions from this topic

Each one with the model answer underneath.

1. 1

   How does the Kekulé model represent the structure of benzene?

   Model answer

   As a hexagonal ring with alternating single and double carbon-carbon bonds.

2. 2

   In the delocalised model of benzene, what type of orbital does each carbon atom contribute to the π-system?

   Model answer

   Each carbon atom has one unhybridised p-orbital perpendicular to the ring plane.

3. 3

   How do the p-orbitals in benzene interact to form the delocalised system?

   Model answer

   Adjacent p-orbitals overlap sideways.

4. 4

   Describe the distribution of electrons in the delocalised model of benzene.

   Model answer

   Electrons are shared across all six carbon atoms, forming two ring-shaped electron clouds above and below the plane of the ring.

5. 5

   What enthalpy of hydrogenation would be predicted for cyclohexatriene based on the Kekulé structure?

   Model answer

   Approximately three times the enthalpy of hydrogenation of cyclohexene.

6. 6

   How does the actual enthalpy of hydrogenation of benzene compare to the predicted value for cyclohexatriene?

   Model answer

   Benzene releases significantly less energy than the predicted value for cyclohexatriene.

What is inside Levo

Six ways to work the same material.

Organic Chemistry III revision questions

What does Organic Chemistry III cover in Edexcel A-Level Chemistry?

10 subtopics: the structure of benzene and the evidence for it, electrophilic substitution of benzene, nitration, halogenation, friedel-crafts and phenol, amines: structure and basicity, reactions of amines and preparing them, amides and condensation polymers, amino acids, zwitterions and proteins, empirical and molecular formulae from analytical data, grignard reagents and multi-step synthesis and purification techniques and the aspirin preparation. Each one has its own page with questions and model answers.

How is Organic Chemistry III organised?

By the Edexcel 9CH0 specification, subtopic by subtopic, so it matches the order you are taught it in.