Colour By Design Flashcards
Atomic emssion spectra
Laser microspectral analysis (LMA) is used to produce a type of emission spectrum to analyze pigment samples
Attaching dyes to fabrics: Direct dyes Acid dyes Other dyes Fibre-reactive dyes
Direct dyes - attach to cotton via h bonding
Acid dyes attach to protein fibers eg silk via ionic bonds
Other dyes attach to fabrics using a mordant - this forms a complex, linking fibre and dye together
Fibre reactive dyes - strong covalent bonds with cotton fabrics.
Stronger the bond between fabric and dye…
The more colour fast the dye will be
Oils and fats are naturally occurring ________ of _______ and ______
Triesters
Propane-1,2,3-triol (glycerol)
And long-chain carboxylic acids
Fatty acids are the ______ in fats and oils
Carboxylic acids
Fatty acids facts and bits
Even number of carbons (16/18)
Unbranched carbon chain
Can be saturated (only C-C) or unsaturated (mix of both or just C=C)
Triesters from largely saturated fatty acids are _____ as there is better packing of the molecules resulting in stronger intermolecular bonds
Largely unsaturated are ___
Solids or fats
Liquids or oils
Hydrolysis of esters
Broken down to sodium salt of the fatty acid (soap) and glycerol by heating with dilute NaOH.
IF FREE ACID IS REQUIRED TREAT SODIUM SALT WITH dilute HCL
Hydrogenation of unsaturated oils
Addition of H, using a nickel catalyst and the correct conditions produces more saturated solid fat. Not all c=c bonds are saturated so gives spreadable fat, still polyunsaturated. Eg of heterogenous catalysis
Molecules that only absorb UV light and transmits all others
Appear colourless as our eyes can’t detect uv
Conjugated system
Has alternate C=C bond to C-C. benzene rings and N=N bonds can also be part of conjugate system
Absorption of uv or visible light causes ______
Electronic transitions - electrons move to higher energy levels and the molecules become excited
Many unsaturated and conjugated systems absorb uv and visible light. The delocalised electrons —-
In these systems require less energy to become excited compared with electrons in single bonds
UV - visible spectroscopy
Spectrometer scans a range of wavelengths of both UV and visible light. Instrument produces a spectrum.
Features of spectrum:
X axis shows wavelength measured in nano meters (1nm = 1X10^-9 m)
Y axis shows intensity of absorption, usually no units
Overall shape is important not individual peaks
Interpreting spectrum from uv spectroscopy absorption
Find wavelength at which absorption is greatest - known as delta max. Colour of solution will be complimentary to this.
Absorption is more intense and the wavelength of delta max increases for..
Organic molecules with large delocalised systems
Reflectance spectra
Used for analyzing a substance that cannot be easily made into a solution. Uv and visible light is shine on the surface and and any reflected light is collected. Used for old paintings. Opposite to absorption spectra.
Chromatography is a method…
Of separating and identifying the components of a mixture
. Eg components that make up old paintings.
Chromatography depend on
equilibrium a set up between stationary phase and mobile phases. Components with a higher affinity for the stationary phase move more slowly.
In G.L.C the stationary phase is _____
Mobile phase is _____
S- A non volatile liquid coated on the surface of finely divided solid particles. This material is packed inside a long thin column, which is coiled inside an oven.
Mobile phase - Unreactive carrier gas and carries mixture through the column.
Examples of inert carrier gases
Nitrogen and noble gases
How does a g.l.c record data
As each component emerges form the Column, a peak is recorded on the chromatogram. The area under each peak is proportional to the amount of that component mixture. Time that a component takes to emerge is called the retention time.
Simplest aren’t is…
Benzene, C6H6, flat hexagonal structure with a bond angle of 120 degrees
Arenas are
Hydrocarbons that contain benzene rings. Their names always end in -Ene, meaning they’re unsaturated.
Who’s structure Is single - bond - single etc
Kekules
Do arenes react with bromine water?
No as they don’t have any c=c bonds, the bonds are delocalised.
Nitrous acid is unstable and made when needed by
Reacting NaNO2 with dilute HCL (aq)
Diazonium ion general formula
R-N+=N
Bond between N is 3
When are diazonium ions stable
When aromatic and even these must be made under temperatures of 5 degrees
Diazotisation reaction -
formation of benzenediazonium ion
Conditions and reactants-
Phenylamine, dilute HCL and sodium nitrate (III) at temperature lower than 5 degrees.
Diazonium ions are
Weak electrophiles, they will attack phenols and aromatic amines (coupling agents) as both are electron rich rings
Coupling reaction
Formation of an -N=N- bond product is an azo compound. Between coupling agent and benzenediazonium ion
Azo compound general formula
R-N=N-R, compounds with R groups are aryl groups are most stable.
Uses of azo compounds
Aromatic azo compounds make excellent fade-resistant dyes. By attaching different functional groups to the chromophore, properties of molecule are modified.
Transition metals and colour
Electrons in the D orbitals can be excited. When transition metal ion is surrounded by ligands the d orbitals ar split into two different energy levels.
Electrons in lower energy levels can be excited to the higher. The excitation energy required corresponds to absorption of visible light.
Factors that could affect the excitation energy and therefore affect the colour :
Type of ligand
Shape of complex -octahedral or tetrahedral
Coordination number of complex
Charge on central transition metal ion
In an isolated transition metal ion…
All the d orbitals and any electrons in them have the same energy
If the d sub shell is empty or full
Transition metal ion is colourless
Chromophore -
Part of the molecule responsible for any colour.
Is an extended delocalised system of electrons obtaining unsaturated groups
