Colour by design

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  • Created by: Gemma
  • Created on: 13-04-14 12:19
Why do some dyes attach themselves to fibres?
Strong electrostatic forces between the dye and fibre. Protein based fibres (silk + cotton) which may contain free ionisable COOH & NH2 groups. These form electrostatic bonds with parts of the fibre e.g. SO3-
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Definition of a colour fast dye?
property of a dye/pigment to keep its original colour without fading
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How can you modify the dye structure to make it stick better to the fibre? ionic
Attach a functional group e.g. SO3-
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How can you modify the dye structure to make it stick better to the fibre? covalent
covalently bond it to another molecule (NH2 group attached to the dye) binds with another molecule - mordant. this then forms covalent bond with the fibre
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definition of a chromophore
part of the molecule which is responsible for colour due to an extended delocalised electron system
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How can you modify the structure of a chromophore +change colour
add a functional group with lone pairs which add to the extended delocalised electron system by interacting with chromophore. Small changes in the delocalised system cause changes in light absorbed + therefore a change in colour
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How can you change the solubility of a dye
Add an ionic group to form ionic groups with a protein based fibre ( can form ion-dipole in water)
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How does adding a functional group to the dye allow it to bond to fibres
Add ionic group
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Describe the features of arenes
Alternating double + single bonds, ring structure, delocalisation - 1 electron from each carbon used in EDED which is represented by the circle in the middle, benzene is very stable due to the electrons being able to get as far away as poss + EDES
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Which experiment proved kekules structure correct?
the bond enthalpy of benzene should be 3X that of cyclohexene - when in fact it's not
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Why are transition metal complexes coloured?
the presence of the ligand surrounding the metal ion/molecule causes the d sub shell to split into 2 different energy levels , so easier transition btwn low + high energy levels , the small energy gaps allow visible light to be absorbed
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What determines the frequency of radiation absorbed + therefore the colour
the gap between the energy levels
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what happens when a molecule absorbs visible radiation
electron is promoted to a higher energy level- goes into one of its several excited states
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Basic principle of absorption spectra
show colours /wavelengths absorbed by a molecule
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basic principle of reflectance spectra
shine light + examine composition of reflected light
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what 3 things are chemist interested about?
the wavelength of radiation absorbed, shape of absorption band & the intensity of absorption (the longer the conjugated carbon chain the more intense and longer the wavelength)
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Stages of GLC
1. sample injected into inert carrier gas 2. column consisting of high b.p. liquid on porous support 3. detection of emerging compounds 4. distinguish compounds by retention time
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What is the mobile phase in GLC?
the inert carrier gas
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What is the stationary phase in GLC?
the particles of solid coated in high m.p. liquid
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The longer the retention time...
the greater the affinity for the stationary phase
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Other cards in this set

Card 2

Front

Definition of a colour fast dye?

Back

property of a dye/pigment to keep its original colour without fading

Card 3

Front

How can you modify the dye structure to make it stick better to the fibre? ionic

Back

Preview of the front of card 3

Card 4

Front

How can you modify the dye structure to make it stick better to the fibre? covalent

Back

Preview of the front of card 4

Card 5

Front

definition of a chromophore

Back

Preview of the front of card 5
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