Colour by design booklet- OCR B Salters

A Booklet on the salters section Colour by design. Detailed notes following the specification. Feel free to contact via get revising mail if anything doesn't make sense to you. Also visit for further resources.

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a) Explain the term electronegativity: recall qualitatively the electronegativity trends of
in the Periodic table. Use knowledge of this to predict bond polarity and hence the
types of bonds to form between molecules/atoms.
Fluorine is the most electronegative element in the periodic table. Electronegativity increases as
you ascend the Periodic table and as you go along from left to right across the Periodic table.
Electronegativity is the ability of an atom/molecule to attract electrons in a bond.
Molecules with O, F and N can generally form Hydrogen bonds with other molecules as they
tend to have a large difference in electronegativity between themselves and the atoms they are
bound too. E.g. O-H, N-H, F-H are all polar bonds.
Molecules with C=O can form permanent dipole-dipole forces between molecules.
Molecules with atoms of a similar electronegativity bound to each other cannot form polar
bonds between molecules. Instead, they form instantaneous dipole-induced dipoles between
b) Suggest and explain in terms of intermolecular bonds, ionic attractions and covalent
bonding, how some dyes attach themselves to fibres.
Dye chains align themselves up next to the fibres and form some kind of bond between
themselves and the fibre. Ionic and covalent bonds would be the strongest type and would
mean that the dye is fast, i.e. it is strongly attached to the fibre and is unlikely to come out
of the fibre in the wash etc. Intermolecular bonds will not be as fast, however hydrogen
bonds will be stronger than the other two types. On top of this, the less branched the
chain, the more closely the dye chains can align to the fibre chains, causing more
intermolecular bonds to form, making the dye most fast.
NOTE: Look out for double bonds in chains. These often cause kinks as there is no rotation
around a double bond... this means often saturated compounds are less flexible and so may
not be able to align up to the fabric chain as easily!!!

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Describe and explain the structure of a dye molecule in terms of the chromophore and:
i) Functional groups that modify the chromophore.
ii) Functional groups which affect the solubility of the dye
iii) Functional groups that allow the dye to bond to fibres
Chromophore: The chromophore is the part of the molecule which causes it to be colourful.
Often it contains unsaturated groups such as C=C, C=O or -N=N-, and are part of an extended
delocalized ring structure, involving arene ring structures .…read more

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See below and chapter 12.3 + 12.4:
i) Recognize arenes and their derivatives (aromatic compounds)
ii) Describe the delocalization of electrons in these compounds.
iii) Explain how delocalization accounts for their characteristic properties (limited
to undergoing substitution rather than addition reactions.
i) Arenes are RINGS, which are stabilized by electron delocalization, like in benzene. The `-ene' tell
you that they are unsaturated like an ALKENE, and the `ar-` comes from AROMATIC, which
means sweet smelling. Arenes are often known as aromatic hydrocarbons.…read more

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Describe and explain the following electrophilic substitution reactions of arenes, naming
the benzene derivatives formed
i) Halogenation of the ring,
ii) Nitration,
iii) Sulfonation,
iv) Friedel-Crafts alkylating and Acylation (including use of ionic liquids).
i) Chlorine and benzene can be substituted into an arene. This reaction uses an anhydrous Al(X)3,
where Al is aluminium and X is the halogen being substituted. The catalyst must be anhydrous as
the catalyst reacts violently with water.…read more

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Bezene-SO2OH + NaOH Benzene-SO3- Na+ + H2O
iv) Alkylation:
An alkyl group is added to the benzene. Benzene is warmed with chloromethane and anhydrous
aluminum chlorine (AlCl3). Methylbenzene is the product!
Benzene and an acyl chloride (or an acid anhydride) are heated together under reflux with AlCl3.
h) Describe and explain the formation of diazonium compounds and coupling reactions that
these undergo to form Azo Dyes.…read more

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NaNO2 (aq) + HCl (aq) HNO2 (aq) + NaCl (aq)
The nitrous acid then reacts with the arlyamine. For example:
+ HNO2 + H+
+ 2H2O
Phenylamine Bezenediazonium Ion
In a diazo coupling reaction, a diazonium salt reacts with another compound containing a
benzene ring called a COUPLING AGENT. The diazonium ion acts as an ELECTROPHILE and reacts
with the bezene ring of the coupling agent.…read more

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Coupling with Phenols:
When a solution of the Benzenediazonium salt is added to an alkaline solution of PHENOL, a
YELLOW-ORANGE azo compound is formed:
With an alkaline solution of naphthalen-2-ol, a red azo compound is produced:
Coupling with Amines:
Diazonium salts also couple with ARYLAMINES such as PHENYLAMINE:
Many different azo compounds can be formed by coupling different diazonium salts with a
whole range of coupling agents. Unlike diazonium salts, the azo compounds are stable so their
colours do not fade.…read more

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Now when light travels through a solution of metal ions surrounded by ligands, a photon of light
may be absorbed. The energy of this photon corresponds to excitation of an electron from a
low energy d orbital to a high-energy d orbital.
The frequency of the light absorbed depends on the energy difference between these two
levels, E. ( E= hv where h is Planck's constant and v is the frequency absorbed.…read more

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The mobile phase is an unreactive gas, such as NITROGEN, called the CARRIER GAS.
The Stationary phase is a small amount of a high boiling point liquid held on a finely divided inert
solid support. This material is packed into a long thing tube called a COLUMN. The column is
coiled inside an oven.
The sample to be analysed is injected into the gas stream just before it enters the column.…read more



Hi, this is an AMAZING reosourse which i would use ... if i was in A2 (so i will save it for next year). do you have one for AS? i really love how u simplified it by using the spec. 

much appreciated if you could let me know if u have one for AS and how to access it :)

Thanks :D


Three years on and this is still so useful.

Thanks, James!

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