Organic Chemistry III | Edexcel A-Level Chemistry (9CH0)

Organic Chemistry III

129 questions
10 subtopics
Paper 2: advanced organic and physical chemistry
Paper 2 and Paper 3

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..

It covers 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.

Sample questions from Organic Chemistry III

Answer each one closed book first, then open the answer.

The structure of benzene and the evidence for it

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

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Approximately three times the enthalpy of hydrogenation of cyclohexene.
Electrophilic substitution of benzene

What reagents are required for the nitration of benzene?

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A mixture of concentrated nitric acid and concentrated sulfuric acid.
Nitration, halogenation, Friedel-Crafts and phenol

In Friedel-Crafts alkylation, how is the carbocation electrophile generated?

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Aluminium chloride accepts a lone pair from the halogen of the halogenoalkane, generating a carbocation.
Amines: structure and basicity

What is the general structure of a primary amide?

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R-CO-NH₂, where the carbonyl carbon is bonded to a nitrogen bearing two hydrogen atoms.
Reactions of amines and preparing them

Why are primary aliphatic amines stronger bases than ammonia?

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Alkyl groups have a positive inductive effect, which increases electron density on the nitrogen and makes the lone pair more available for protonation.
Amides and condensation polymers

What type of linkage is present in the repeat unit of a polyester?

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Ester linkages (-COO-).
Amino acids, zwitterions and proteins

In what form do 2-amino acids predominantly exist in aqueous solution?

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As zwitterions.
Empirical and molecular formulae from analytical data

When determining empirical formula from percentage composition, what is the first step for each element?

Show the answer
Divide the percentage of each element by its relative atomic mass to obtain a molar ratio.

The 10 subtopics

One subtopic is one session. Work down the list.

Subtopic	What it covers	Questions
The structure of benzene and the evidence for it	Recall questions on the Kekulé structure and the delocalised model, and on the bond lengths, hydrogenation enthalpies and lack of reactivity that decide between them.	12
Electrophilic substitution of benzene	The 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.	11
Nitration, halogenation, Friedel-Crafts and phenol	The 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.	17
Amines: structure and basicity	The 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.	12
Reactions of amines and preparing them	Amines 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.	12
Amides and condensation polymers	Acyl 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.	10
Amino acids, zwitterions and proteins	Peptide 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.	12
Empirical and molecular formulae from analytical data	Empirical 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.	14
Grignard reagents and multi-step synthesis	Recall questions on preparing and using a Grignard reagent, on how it lengthens a carbon chain, and on planning a route between two functional groups.	12
Purification techniques and the aspirin preparation	Reflux, 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.	17

Organic Chemistry III is 129 of the 1,534 questions in the guide.Get the guide, £8

How the guide is worked

Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.

Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.

Read the full method, the return schedule and the research behind it.