F335 Colour by Design

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How do direct dyes attach to cotton?
Hydrogen bonds
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How do acid dyes attach to protein fibres (i.e. silk)?
ionic bonds
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What's a mordant and why's it used?
Forms a complex between dyes and fabrics, linking them together
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What do fibre-reactive dyes form with cotton fabrics?
Strong covalent bonds
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What are oils and fats?
Naturally occurring triesters of propane-1,2,3-triol (glycerol) and long-chain carboxylic acids (fatty acids)
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What are fatty acids?
The carboxylic acids found in fats and oils. Have an even number of carbons in unbranched chain. Can be saturated or unsaturated.
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How can fat or oil be broken down into the sodium salt of the fatty acid (soap) and glycerol?
Heating with concentrated sodium hydroxide solution
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What does hydrogenation do?
Produces a more saturated solid fat, which can be used in the manufacture of margarine. Not all of the C=C are hydrogenated, giving a spreadable fat. This process uses a nickel catalyst.
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Why do some molecules appear colourless?
Many molecules absorb UV radiation rather than invisible light. Our eyes don't detect UV and a molecule that only absorbs UV (and transmits all visible wavelengths) appears colourless.
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What does absorption of UV or visible light cause?
Electron transitions in molecules. Electrons move to higher energy levels and the molecule becomes excited
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What certain types of molecules absorb UV and visible light easily and why?
Many unsaturated molecules and those with conjugated systems (alternating C=C and C-C bonds). Because the delocalised electrons in these systems require slightly less energy to be come excited than electrons in single bonds.
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Describe gas-liquid chromatography
The stationary phase is a non-volatile liquid coated on the surface of finely divided solid particles. This material is packed inside a long thin column, coiled inside an oven. Unreactive carrier gas acts as mobile phase and takes it through column
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How is the result formed in gas-liquid chromatography?
As each component emerges, a peak is recorded on the chromatogram. The area under each peak is proportional to the amount of that component in the mixture. The time a component takes is called the retention time
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What types of reactions do arenes usually undergo?
Substitution reactions, very rarely addition. Usually electrophilic substitution
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What are the reagents and conditions for the nitration of benzene?
Benzene + c. HNO3. Temp < 55 degrees C, with c. H2SO4
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What are the reagents and conditions for the sulfonation of benzene?
Benzene + c. H2SO4. Heated under reflux
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What are the reagents and conditions for the chlorination of benzene?
Benzene + Cl2. Anhydrous AlCl3. Room temp
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What are the reagents and conditions for the bromination of benzene?
Benzene + Br2. Anhydrous iron (III) bromide (FeBr3) or iron filings. Room temp.
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What are the reagents and conditions for the alkylation of benzene?
Benzene + chloralkane. Anhydrous AlCl3. Heat under refux.
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What are the reagents and conditions for the acylation of benzene?
Benzene + acyl chloride. Anhydrous AlCl3. Heat under reflux.
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What are these alkylation and acylation reactions known as and what are their benefits?
Friedel-Crafts reactions. Can be carried out in ionic liquids as combination solvent-catalyst systems. These reduce solvent emissions + flammability, recycle easily, allow reactions to be carried out at reduced temp
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What's the general formula for diazonium ions? And what types are stable?
R-N+(triplebond)N. Only aromatic diazonium ions are stable and still have to be made in solution
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What are the reactants and conditions for diazotisation?
phenylamine, dilute hydrochloric acid, sodium nitrate(III), temp below 5 degrees C
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Describe the formation of azo compounds
Diazonium ions = weak electrophiles. They attack phenols and aromatic amines (coupling agents). An -N=N- bond is formed. It's a coupling reaction
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What makes an azo dye coloured?
The chromophore. Aromatic azo compounds make great fade-resistant dyes
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How does adding -SO3 - Na + to a chromophore modify its properties?
Solubility in water is improved. Can form ionic bonds with protein fibre such as wool
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How does adding -NH2 or -NR2 to a chromophore modify its properties?
Colour is modified or enhanced
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Why are many transition metal ions coloured?
Electrons in their d orbitals can be excited. When it's surrounded by ligands, the d orbitals are split into 2 different energy levels. Electrons in the lower can be excited to the higher. Energy required corresponds to absorption of light.
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What factors effect the excitation energy, and therefore the colour of the complex?
Type of ligand; shape of the complex; coordination number; charge on the central transition metal ion
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Why are these molecules sometimes colourless?
If the d sub-shell is empty or completely full
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What part of an organic molecule is responsible for colour and why?
The chromophore. System of delocalised electrons that don't need much energy to become excited. This energy is available when the molecule absorbs light
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Card 2

Front

How do acid dyes attach to protein fibres (i.e. silk)?

Back

ionic bonds

Card 3

Front

What's a mordant and why's it used?

Back

Preview of the front of card 3

Card 4

Front

What do fibre-reactive dyes form with cotton fabrics?

Back

Preview of the front of card 4

Card 5

Front

What are oils and fats?

Back

Preview of the front of card 5
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