Colour by Design

Colour by Design

1. Forces of attraction

   • Instantaneous Dipole-Induced Dipole
     • Same polarity/electronegativity
     • Two molecules such as H move together, electrons do not stay in one place/ evenly distributed.
       • Electrons move towards one side for an instants which causes a charge in the molecule. The molecule moves towards another which causes the electons to move to another side of the molecule which induces a charge.
     • The bigger the molecule, the more electrons therefore the higher polarity
   • Permanent Dipole-Permanent Dipole
     • Occurs with two molecules which have two very different electronegativity's
     • They bond together due to their differences in charges
   • Hydroygen
     • Electronegativity of N,F,O
     • Lone pair of electrons
     • Strongest intermolecular force

2. Pigments-insoluble, sit on the surface

   • Dyes- soluble, bond between the molecules
   • Chromophore- functional group on a molecule which causes the colour of the molecule

3. Stability of electons

   • Carboxylic Acids have lone pairs of electrons, they react with sodium carbonate fizzing and no don't react with iron chloride)
   • Phenols have benzene rings which allow it to react with iron chloride turning the solution purple
     • Benzene ring is drawn as a continuous circle as the bonds are 1 and a half in length, not a c-c or a c=c. All of the bonds are equal in this length.

4. Mechanisms

   • Freidel- craft
   • Nitration
   • Sulfonication

5. Azo-dye formation

   • 1-Nitration of benzene ring
   • 2-Reduction to nitrobenzene
   • 3-Phenylamine to diazonium ion
   • 4-diazonium salt to azo dye

6. D-orbital

   • Splitting of the d-orbital allows movement of electrons from the lower to the higher split orbital. The difference in energy gap between the two orbitals corresponds to a frequency and wavelength of the colour which the molecule produces.
   • The transition metals only produce colour if the d-orbitals are partially filled,

7. Gas-liquid chromotography

   • The sample is injected into the carrier gas when it enters the column
   • The components distribute itself between the different phases at different extents so emerge out of the column at different times
     • They do this by having a greater affinity to the high boiling point liquid which is finely dispersed on the solid within the columns or to the inert carrier gas.
   • The solvents which dissolve in the stationary phase more readily so emerge from the chamber slower.
   • The carrier gas needs to be an unreactive gas
   • Movement of samples

8. Absorption/Emission Spectra

   • Black background with coloured line show the emission of light
   • A coloured background with black lines show the absorption of light

9. UV-Vis Spectroscopy

   • Monochromatic light, splits into two beams. One of the beams goes through the sample material and the second goes through the reference material. The beams are sent on the same path in separate alternative pulses using a beam chopper. The beams are then compared to give an absorption spectra.
     • If a sample absorbs UV radiation, it will appear colourless to the human eye
       • The feature of the spectrum are the intensity of absorption which is related to the concentration of the solution, the wavelength and the shape of the absorption band which determines the shade and purity of the colour.

10. Fats and Oils

    • Fats and Oils are naturally occurring triesters of propan-1-2-3-triol (glycerol). Fatty acids are solids at room temperature due to the fact they are mainly saturated straight chains which can pack close together forming strong intermolecular forces
    • Oils are liquids at room temperature as they have weaker intermolecular forces so can not pack as closely together due to the unsaturated chains containing double bonds
      • Natural oils are fats can be broken down into sodium salt of the fatty acid and glycerol using dilute sodium hydroxide whilst being heated.
        • Hydrogenation- the addition of hydrogen atoms to an unsaturated fat/oil to break the double bonds at 180 degrees using a nickel catalyst. This process is used when margarine is made.
        • Iodine Number- The scale in which how much ICl reacts with an fatty acid. The more ICl that reacts the higher the iodine number and the greater the drying potential the oil has. The more unsaturated the oil the higher it's drying potential is.

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