Colours by design

• What do amine group dyes work best with and why?

  works well with cellulose fibres (e.g., cotton, rayon and linen) as they have lots of OH groups
• How colour fast are amine group dyes and why?

  hydrogen bonds aren't strong enough so aren't very colour fast
• How do dyes with amine groups attach themselves to fibres?

  Functional group enables dye molecules to form hydrogen bonds with fibre molecules
• How do dyes with acidic groups attach themselves to fibres?

  They help to bind to alkaline -NH- links in fibres, H+ ions move from dye to fibre molecule, ionic interactions hold them together
• What do acidic group dyes work best with and why?

  wool, silk and nylon because they accept H+ ions
• How colour fast are acidic group dyes and why?

  Better colourfastness than dyes that form hydrogen bonds because they form ionic bonds which are stronger.
• How do dyes with ionic salt groups attach themselves to fibres?

  They help to bind to alkaline -NH- links in fibres. The salt group dissociates when you dissolve the dye in water to give SO₃⁻. To make -+NH2- group, need to add acid to provide H+ ions to -NH- links. The SO₃⁻ groups will then bind to the -+NH2- links
• What do ionic salt group dyes work best with and why?

  wool, silk and nylon because they accept H+ ions
• How colour fast are ionic salt group dyes and why?

  Better colourfastness than dyes that form hydrogen bonds because they form ionic bonds which are stronger.
• What is a chromophore?


  the colored portion of the dye
• What do chromophores tend to contain?

  double or triple bonds, lone pairs of electrons or benzene rings
• What happens when you modify a chromophore?

  it will change its frequency of light that it absorbs so it will change the colour of the molecule
• What happens when light hits a chromophore?

  certain wavelengths are absorbed by electrons in the chromophore, visible wavelengths not absorbed will be seen as a particular colour
• What functional groups would modify a chromophore and why?

  ones containing O or N atoms with lone pairs of electrons because the lone pair of electrons becomes part of the delocalised system responsible for absorbing light
• What functional groups would affect the solubility of the dye?


  ionic groups such as the sulfate ion (usually in the form of its sodium salt)
• Why does water dissolve ionic substances?


  because it is polar, the partial charges on water or hydrogen can sometimes be enough to pull ions away from a lattice if they bonds that would form between the water and ion is stronger than the bonds between the ions.
• What functional groups allows a dye to bond to fibres?

  ammine, acidic, ionic salts
• What do fats and oils consist of mainly?


  mixed esters of propane-1,2,3-triol with varying degrees of unsaturation
• Where are the delocalised electrons in benzene and why are they arranged like this?


  in p orbitals above and below the plane of the ring and so the electrons have more room, they can get further away from each other this spread out the negative charge so the molecule is more stable

  
• How was Kekule's structure disproved?

  His figure showed 3 C-C bonds and 3 C=C bonds, this would mean that the bond lengths that would be slightly different but X-rays have shown that the bond lengths are all the same.
• Why happens when you add bromine to benzene?

  nothing, the orange colour remains
• Why doesn't benzene like addition reactions but likes substitution reactions?


  because addition reactions need to take electrons from the stable delocalised ring to form new bonds but with substitution reactions just a hydrogen atom gets swapped for something else so the stability of the delocalised electrons is preserved
• Shape of benzene


  planar

  
• Bonding in benzene


  p-orbitals on carbon atoms overlap to form a delocalised pi-bonding ring
• What is hydrogenation?
• Halogenation of benzene mechanism

  Electrophilic substitution

  
• Nitration of benzene


  Electrophilic substitution

  Produces nitrobenzene

  
• Sulfonation of benzene


  electrophilic substitution

  fuming H2SO4/SO3, 40*C

  
• Friedel-Crafts Alkylation of Benzene


  electrophilic substitution

  halogenoalkane, dry and in presence of anhydrous AlX

  
• Friedel-Crafts Acylation of Benzene


  electrophilic substitution

  acyl chloride, dry and in presence of anhydrous AlCl3

  
• How do you make a diazonium salt?


  - make nitrous acid first: NaNO2 + HCl -> HNO2 + NaCl

  - temp must be below 5 degrees to stop phenol forming

  - aminebenzene + HNO2 + HCl -> diazonium salt + 2H2O
• What does a diazonium ion look like?

  
• How do you make an azo dye?


  - dissolve phenol in NaOH

  - stand in ice, add chilled benezenediazoniumchloride
• What type of reaction occurs in making an azo dye?

  coupling reaction
• Why do diazonium ions attack phenols?


  - the lone pairs on oxygen increase the electron density of the benzene ring, particularly carbon 2,4 and 6

  - this gives the d ion, as a weak electrophile, something to attack
• What does colourfast mean and what does it depend on?


  - a material's resistance to fading or running

  - depends on the bonding between the dye and the fibre
• Describe the process of Gas-Liquid chromatography.


  1. inject liquid sample then vaporise it

  2. use an inert carrier gas to push it through a coiled tube

  3. sample travels through tube to detector which records how much is detected and how long it takes to detect
• What is the retention time?


  the time it takes a component in a mixture to pass through the column during gas chromatography
• What is the stationary phase and mobile phase in gas-liquid chromatography?


  - stationary - tube with high boiling liquid on sides

  - mobile - inert carrier gas
• What is the first peak on the chromatogram?

  the solvent