Colour by Design

HideShow resource information
  • Created by: Sabina
  • Created on: 07-04-16 14:19
What are arenes?
Aromatic compounds containing a benzene ring
1 of 68
What was Kekule's structure?
Kekule suggested that the single and double bonds in a planar ring continuously alternated between the carbons
2 of 68
How was Kekule's structure disproved?
There should be three bonds with the C-C bond length and three with the C double bond C length. However when x-rayed it was shown that all bonds had the same length.Also did not react with bromine,doesn't undergo electrophilic addition
3 of 68
What is the delocalised structure?
Within a planar ring there is a ring of delocalised electrons. The carbons still arranged in a ring but no alternating single and double bonds. Instead each carbon donates an electron from its p-orbital which form a ring of delocalised electrons
4 of 68
What type of reaction does a benzene ring undergo?
electrophilic substitution
5 of 68
What happens if you add bromine to benzene
6 of 68
What are functional group does a fatty acid contain?
Carboxylic acid and alkene if it is unsaturated
7 of 68
What are triglycerides?
Triesters of glycerol and fatty acids
8 of 68
What type of reaction do 3x fatty acids and glycerol undergo to form a triglyceride?
9 of 68
Why does benzene react by substitution but not addition?
Electrons in a benzene ring spread out the negative charge so that the molecule is more stable. Addition would need to remove electrons from the stable ring to form new bonds, substitution just swaps H for something else preserving stable ring
10 of 68
Give the reagents and conditions of nitration
Reagents:Concentrated nitric and sulphuric acid Conditions: Temperature below 55 degrees
11 of 68
What is produced by nitration?
Nitrobenzene and H+ which reacts with HSO4- to reform the catalyst back into sulphuric acid
12 of 68
What acts are the electrophile in nitration?
Nitronium ion (NO2^+)
13 of 68
What does concentrated sulphuric acid do during nitration?
Acts as a catalyst
14 of 68
What happens if the temperature exceeds 55 degrees in nitration?
You will get more than one nitro group substituted into the benzene ring
15 of 68
Why won’t you get much trinitrobenzene formed?
NO2 groups make the ring much less reactive than benzene itself. By the time you get two NO2 groups attached, the ring is so unreactive that getting a third one attached is very slow.
16 of 68
The nitration of methylbenzene happens about 25 times faster than the nitration of benzene. Explain why.
Methyl groups “push” electrons away from themselves towards the ring, increasing the electron density in the ring. That makes it much more attractive to the sort of things which the ring reacts with.
17 of 68
Give the reagents and conditions of sulfonation
Reagents:Concentrated sulphuric acid or fuming sulphuric acid Conditions:Reflux or 40 degrees
18 of 68
What is produced by sulfonation?
Benzenesulfonic acid
19 of 68
What is the electrophile in sulfonation?
Sulfur trioxide (SO3)
20 of 68
Why is sulfur trioxide an electrophile?
It is a highly polar molecule. The sulfur atom has a partially positive charge causing it to be attracted to the ring of electrons
21 of 68
Where does the sulfur trioxide come from in sulfonation?
Conc. sulfuric acid is dissociated into sulfur trioxide and water. Fuming sulfuric acid is a solution of lots of sulfur trioxide molecules dissolved in sulfuric acid
22 of 68
What is dissociation?
The reversible splitting up of a compound
23 of 68
What are alkyl groups?
A group that has one few H than an alkane group
24 of 68
What is an acyl group?
An alkyl group attached to C-O double bond
25 of 68
What are the reagents and conditions of Friedel-Crafts acylation?
Reagent:Aluminium Chloride Conditions:Reflux
26 of 68
What is the electrophile in Friedel-Crafts acylation?
Acylium ion
27 of 68
How is an acylium ion formed in Friedel-Crafts acylation?
Formed by the reaction between the acyl chloride and aluminium chloride catalyst
28 of 68
What is produced from Friedel-Crafts acylation?
Phenyketone, HCl and aluminium chloride
29 of 68
What are the reagents and conditions of Friedel-Crafts alkylation?
Reagents: Aluminium chloride Conditions:Reflux
30 of 68
What is a carbocation?
An organic ion with a positively charged carbon atom
31 of 68
What is the electrophile in Friedel-Crafts alkylation?
32 of 68
How is the carbocation formed in Friedel-Crafts alkylation?
Reaction between chloroalkane and aluminium chloride
33 of 68
What is produced from Friedel-Crafts alkylation?
Alkyl benzene e.g. methylbenzene, HCl and aluminium
34 of 68
Reagents and conditions of halogention
Reagent:Aluminium chloride or iron Conditions:room temperature
35 of 68
What is the electrophile in halogenation?
Partially positive end of halogen molecule
36 of 68
How does iron become a catalyst in halogenation?
Reacts with bromine or chlorine to form iron(III) chloride or iron(III) bromide
37 of 68
What is produced by halogenation?
Bromobenzene or chlorobenzene, HBr or HCl
38 of 68
When will benzene undergo an addition reaction with chlorine or bromine?
In the presence of UV. Ring of delocalised electrons is permanently broken and Cl or Br is added on to each carbon atom
39 of 68
Why are electrophilic substitution reactions of benzene relatively slow?
It needs quite a lot of energy to break the delocalisation on the ring and form the intermediate ion. That means that the activation energy for the overall reaction is high, and so relatively few particles will have enough energy to react
40 of 68
What are aromatic amines used to make?
Azo dyes
41 of 68
What are azo dyes?
man-made dyes that contain the azo group (-N double bond N-). This azo group is usually used to link two aromatic compunds
42 of 68
How is an azo dye made?
First a diazonium salt is made. The diazonium salt is then coupled with an aromatic compound that is susceptible to an electrophilic attack e.g. phenol
43 of 68
How is a diazonium salt formed?
Sodium nitrate and hydrochloric acid are reacted together to form nitrous acid. Nitrous acid is then reacted with phenylamine and HCl to form benzenediazonium chloride. Temperature must be below 10 degrees
44 of 68
Describe the process of coupling benzenediazonium chloride with a pheno
Phenol is dissolved in a sodium hydroxide solution to make a sodium phenoxide solution.Cool solutution then add benzenediazonium chloride added.Azo dye precipitates out of the solution immediately
45 of 68
Why is phenol a coupling agent?
The lone pairs on its oxygen increase the electron density of the benzene ring making it easier for the diazonium ion which is a weak electrophile to bond to it.
46 of 68
What are the most permanent types of dyes
Dyes that have a functional group that will react with -OH of -NH in the fibre, forming strong covalent bonds.
47 of 68
What is a chromophore?
A part of an organic molecule that causes it to be coloured
48 of 68
How does a chromophore give an azo dye its colour?
Azo compounds contain highly delocalised system of electrons. If light falls on the molecule some wavelengths are absorbed by the delocalised electrons,which the chromophore is part of. The colour seen is complimentary to frequency of colour absorbed
49 of 68
What will happen if a chromophore is modifyed?
Will cause a change in the frequency of light absorbed thus changing the colour of the molecule
50 of 68
What can be done to adjust the colour of the dye molecule?Why?
Add functional groups containing O or N atoms with lone pairs of electrons. This is added as the lone pair of electrons becomes part of the delocalised system responsible for absorbing light
51 of 68
What happens when an acid is added to methyl orange?
A hydrogen ion is gained causing it to become red
52 of 68
What happens if an alkali is added to methyl orange?
A hydrogen ion is lost causing it to become yellow
53 of 68
How is the solubility of a dye in water increased?
Ionic groups are added to the dye molecule these are often ionic groups e.g. sulfate ion. Water dissolves the ionic substances due to its polar nature
54 of 68
Name two binding mediums
Oil and water
55 of 68
Describe gas-liquid chromotography
Sample injected into stream of carrier gas which carries it through the tube to the stationary phase.Mixture dissolves in stationary phase, evaporates in mobile phase and redissolves in tube. Solubility determines how long in stationary phase
56 of 68
What gas is used as the mobile phase in GLC?
unreactive gas e.g. nitrogen or helium
57 of 68
What is retention time?
The time taken to reach the detector
58 of 68
What does the area under the peak in GLC show?
The relative amount of each substance in the original mixture
59 of 68
What can GLC be combines with to make it a better analytical tool?
Mass spectroscopy
60 of 68
What happens if GLC is combines with mass spectroscopy?
Sample is separated by GLC. The separated components then go into a mass spectrometer. The spectrometer produces a mass spec for each component which can then be identified
61 of 68
Describe how visible absorption spectrum is produced
Beam of monochromatic light is passed through a dilute solution of the pigment.A detector measures the amount of light absorbed by pigment. Different frequencies of light passed through solution showing which colour absorbed most strongly
62 of 68
When is visible absorption spectroscopy used?
If you have a dilute solution of the pigment
63 of 68
When is a visible reflection spectroscopy used?
If you are not able to make a solution of the pigment
64 of 68
Describe how a visible reflection spectrum is produced
A beam of monochromatic light is shone onto the surface of a solid. The reflectance is measured. By changing the frequency of light and calculating reflectance a visible spectrum is produced
65 of 68
Describe how an atomic emission is produced
High-energy pulse of light focused onto a tiny sample of paint causing pigment to vapourise.Vapour passed between two electrodes.Energy excites electrons in pigment->return to ground state->emit light with specific frequency.
66 of 68
What is an electrophile?
Molecule with a partially positive charge that accepts a pair of electrons.
67 of 68
Describe the arrangement of delocalised electrons in a benzene ring.
Two rings one is above the carbon atoms and one is below
68 of 68

Other cards in this set

Card 2


What was Kekule's structure?


Kekule suggested that the single and double bonds in a planar ring continuously alternated between the carbons

Card 3


How was Kekule's structure disproved?


Preview of the front of card 3

Card 4


What is the delocalised structure?


Preview of the front of card 4

Card 5


What type of reaction does a benzene ring undergo?


Preview of the front of card 5
View more cards


No comments have yet been made

Similar Chemistry resources:

See all Chemistry resources »See all unit 5 resources »