Colour by Design | OCR A-Level Chemistry B (Salters) (H433)

Colour by Design

312 questions
20 subtopics
The ten storylines, examined across all three papers
Component 01, Component 02 and Component 03

The final storyline, which carries the arenes and the rest of the organic chemistry: how a dye attaches to a fibre, fats and oils, benzene and electrophilic substitution, azo dyes, the carbonyl compounds, planning a synthetic route, why organic molecules are coloured, and gas-liquid chromatography..

It covers how dyes attach to fibres, structure of a dye molecule, fats and oils, arenes and delocalisation, representations of benzene and enthalpy of hydrogenation, tests for the common functional groups, identifying a polyfunctional molecule from a set of test results, halogenation and nitration of benzene and the electrophiles involved, the nitration mechanism, sulfonation and the Friedel-Crafts reactions, diazotisation and why it is done cold, coupling reactions, azo dyes and the route from benzene, oxidising an aldehyde and the three carbonyl tests, cyanohydrin formation and its use in synthesis, using the Data Sheet reactions to plan a route, choosing between routes on yield and atom economy, nucleophilic addition mechanism, classifying organic reactions and unfamiliar mechanisms, origins of colour in organic molecules, how gas-liquid chromatography separates a mixture and retention time, peak area and the limits of the technique.

Sample questions from Colour by Design

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

How dyes attach to fibres

Describe how an acid dye bonds to wool.

Show the answer
The dye's negatively charged sulfonate groups form ionic bonds with positively charged –NH₃⁺ groups on the protein chains of the wool.
Fats and oils

Why does bromine water lose its colour with an unsaturated oil?

Show the answer
Bromine adds across the carbon–carbon double bonds, so the coloured bromine is used up.
Tests for the common functional groups

How can a carboxylic acid be distinguished from a phenol in a test tube?

Show the answer
Add sodium carbonate solution; the carboxylic acid effervesces as carbon dioxide is released, while the phenol does not react.
Halogenation and nitration of benzene and the electrophiles involved

Name the products of the nitration of benzene.

Show the answer
Nitrobenzene, C₆H₅NO₂, together with water.
Coupling reactions, azo dyes and the route from benzene

Explain why azo dyes are so intensely coloured.

Show the answer
The delocalisation runs across both rings and the azo group, so the gap between electronic energy levels is small and visible light is absorbed strongly.
Cyanohydrin formation and its use in synthesis

Why is cyanohydrin formation so useful to a synthetic chemist?

Show the answer
It lengthens the carbon chain by one atom and installs both an –OH group and a –CN group that can each be converted further.
Nucleophilic addition mechanism

Why must the second curly arrow be drawn in that first step?

Show the answer
Carbon can form only four bonds, so as the new carbon–carbon bond forms the π bond must break, its pair of electrons moving onto the oxygen.
Origins of colour in organic molecules

Dye A absorbs at 430 nm and dye B at 520 nm. Calculate the energy gap in each molecule.

Show the answer
For dye A the gap is 4.63 × 10⁻¹⁹ J and for dye B it is 3.83 × 10⁻¹⁹ J.

The 20 subtopics

One subtopic is one session. Work down the list.

Subtopic	What it covers	Questions
How dyes attach to fibres	Recall questions on why a dye must bond rather than sit on the fibre, why such molecules are long and flat, and why the weakest-bound dyes wash out.	19
Structure of a dye molecule	Recall questions on the chromophore, the effect of electron-donating and electron-withdrawing groups, and the role of solubilising groups.	20
Fats and oils	Recall questions on triesters and fatty acids, saturated against unsaturated chains, testing an oil for unsaturation, hardening, and hydrolysis.	19
Arenes and delocalisation	Recall questions on what an arene is, the formulae of benzene and its derivatives, delocalisation, and why benzene does not decolourise bromine water.	21
Representations of benzene and enthalpy of hydrogenation	Recall questions on the Kekulé and delocalised models, the equal bond lengths, and the hydrogenation enthalpy evidence for delocalisation.	22
Tests for the common functional groups	Recall questions on the reagents and observations for a C=C bond, a phenol, a carboxylic acid, an aldehyde, a ketone and each class of alcohol.	14
Identifying a polyfunctional molecule from a set of test results	Recall questions on what a polyfunctional molecule is, why tests are done one at a time, and deducing the groups present from a set of results.	12
Halogenation and nitration of benzene and the electrophiles involved	Recall questions on the reagents and conditions for each, the halogen carrier, and generating the nitronium ion.	12
The nitration mechanism, sulfonation and the Friedel-Crafts reactions	Recall questions on the two steps of the nitration mechanism, sulfonation and why a dye manufacturer wants it, and the alkylation and acylation reagents.	14
Diazotisation and why it is done cold	Recall questions on the starting material and reagents, why nitrous acid is made in the mixture, the temperature, and what happens if it rises.	12
Coupling reactions, azo dyes and the route from benzene	Recall questions on what couples with a diazonium ion and where, the azo group, why azo dyes are intense, and the full route from benzene.	11
Oxidising an aldehyde and the three carbonyl tests	Recall questions on the dichromate oxidation and its colour change, why ketones resist it, and the Tollens' and Fehling's results for each.	15
Cyanohydrin formation and its use in synthesis	Recall questions on the reagent, the product and its class, why the reaction is useful for lengthening a chain, and the safety precaution.	9
Using the Data Sheet reactions to plan a route	Recall questions on the reagents and conditions for each Data Sheet reaction, and on stringing them into a multi-step route.	14
Choosing between routes on yield and atom economy	Recall questions on multiplying step yields, why fewer steps are preferred, and comparing two routes on atom economy.	12
Nucleophilic addition mechanism	Recall questions on why the carbonyl carbon is electron-deficient, the partial charges, the curly arrows, and why the reaction is nucleophilic addition.	19
Classifying organic reactions and unfamiliar mechanisms	Recall questions on naming a reaction type from what happens, and on working through a mechanism that has not been met before.	22
Origins of colour in organic molecules	Recall questions on what absorption does to a molecule, the energy and frequency relationships, the chromophore, and the effect of extending conjugation.	22
How gas-liquid chromatography separates a mixture	Recall questions on the mobile and stationary phases, the carrier gas, the heated injection port, the column, and what causes separation.	10
Retention time, peak area and the limits of the technique	Recall questions on retention time and its conditions, using peak areas for composition, the limitation of retention time alone, and coupling to a mass spectrometer.	13

Colour by Design is 312 of the 3,430 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.