Colour by Design Flashcards
1
Q
what is the formula for benzene?
A
C6H6
2
Q
if Kekule’s structure for benzene was correct there should be…
A
3 bonds with the C-C length bond and 3 bonds with the C=C length bond
3
Q
why was Kekules structure wrong?
A
all the C-C bonds in benzene are the same length
4
Q
explain the structure of the delocalised model of benzene
A
the carbons are arranged in a ring
each carbon donates an electron from its p orbital. the p orbitals combine to form a ring of delocalised electrons
5
Q
ethene + bromine is an example of what kind of reaction?
A
electrophilic addition
6
Q
in the reaction ethene + bromine what is produced?
A
1,2- di bromoethane
7
Q
why is benzene stable?
A
the electrons in the delocalised ring can get further away from each other so the negative charge is more spread out
8
Q
when you warm benzene with concentrated nitric and sulfuric acid you get….
A
nitrobenzene
9
Q
halogen carriers help to make good….
A
electrophiles
10
Q
how do halogen carriers help to make electrophiles with polar molecules?
A
halogen carrier accepts a lone pair of electrons from the polar molecule containing a halogen. the lone pair of electrons pulls away the polarisation in electrophile increases, sometimes a carbocation forms
11
Q
what is a carbocation?
A
an organic ion with a positively charged carbon atom
12
Q
halogen carriers can be put an alkyl group on…
A
benzene
13
Q
how can methylbenzene be made?
A
- carbocation formed from chloroalkane and AlCl3
- then the carbocation reacts with benzene via electrophilic substitution
- the halogen carrier gets regenerated when AlCl4- reacts with the H+ ion comes off the benzene
14
Q
what type of reaction is the method to put an alkyl group on a benzene ring?
A
friedel-crafts alkylation
15
Q
the general reaction when an alkyl group is put on a benzene is…
A
C6H6 + RCl –> C6H5R + HCl
catalyst - AlCl3
reflux
16
Q
what conditions are needed to put an alkyl group on a benzene?
A
reflux
17
Q
halogen carriers help halogens….
A
substitute onto a benzene ring
18
Q
how do halogen carriers help halogens substitute into the benzene ring?
A
- halogen carriers polarise halogen molecules
- the +vely charges end of the halogen acts as an electrophile and reacts with the benzene ring
- electrophilic substitution reaction
19
Q
what type of reaction is halogen substituting onto a benzene ring?
A
electrophilic substitution
20
Q
halogen carriers can put acyl groups…
A
on benzene
21
Q
what is the method for substituting a acyl group on a benzene?
A
- acylium ion is formed from acyl chloride and AlCl3
- the acylium ion acts as the electrophile and goes to react with benzene
- AlCl3 then gets regenerated
22
Q
when an acyl group is substituted for a H atom on benzene what conditions are needed?
A
reflux
23
Q
azo dyes are man made dyes that contain the azo group. the azo group is….
A
-N=N-
24
Q
in azo dyes the azo group links…
A
two aromatic groups
25
why does delocalisation extend across the whole dye molecule?
it contains two aromatic groups making it very stable. the azo group becomes part of the delocalised electron system
26
what type of reaction makes an azo dye?
a coupling reaction
27
what are the 2 steps to making an azo dye?
1. react phenylamine with nitrous acid to make a diazonium salt
2. make the azo dye by coupling the diazonium salt with phenol
28
how is a diazonium salt made?
1. HNO2 is made in situ from sodium nitrate and HCl
2. HNO2 reacts with phenylamine and HCl to form benzenediazonium chloride.
it must be done below 5 degrees
29
when a diazonium salt is made why does it have to be carried out below 5 degrees?
to prevents a phenol forming instead
30
how is an azo dye made by coupling the diazonium salt with a phenol?
1. phenol dissolved in NaOH to make sodium phenoxide solution
2. stand it in ice and add chilled diazonium salt
3. the azo dye precipitates out of the solution immediately
31
what does colourfast mean?
a dye cant wash out too easily or fade in the light
32
which part of a dye binds to the fabric?
its functional group
33
dyes that contain the amine group bind best to what material?
cotton rayon and linen
34
why do dyes with amine groups bond to cotton, rayon and nylon best?
NH2 form H bonds with OH groups. there are many OH groups groups in these materials.
35
are dyes with the functional group NH2 bound to the material strong? why?
no
hydrogen bonds aren't strong enough
36
dyes that contain acidic groups bind best to what materials?
wool, silk and nylon
37
how do dyes with acidic groups join to wool, silk and nylon?
the acidic group binds to the -NH- links in fibres. the H+ ions move from dye to fibre molecule and ionic interactions hold them together
38
dyes that contain ionic salt groups bind best to what materials?
wool, silk and nylon
39
how do dyes with ionic salt groups bind to wool, silk and nylon?
bind with the -NH- links. the salt groups dissociate in when you dissolve the dye in water then acid is added to provide H+ to the NH links so slat groups will bind
40
the most permanent type of dye is....
fibre reactive dyes
41
why are fibre reactive dyes the most permanent type of dye?
they have a functional group that will react with the OH or NH group in the fibre, forming strong covalent bonds
42
what part of a dye molecule gives the dye its colour?
the chromophore
43
when light hits a chromophore how is light seen?
certain wavelengths are absorbed by electrons in the chromophore. visible wavelengths not absorbed will be seen as a particular colour
44
how does modifying the chromophore change the colour of a molecule?
it will change the frequency of light it absorbs
45
when functional groups conatining O and N are added to the chromophore why does the molecules colour change?
the lone pair of electrons becomes part of the delocalised system responsible for absorbing light
46
what groups are sometimes added to dyes to make them more water soluble?
ionic groups
47
how does light appear colored?
when electrons absorb light energy (UV or visible light) they are excited to higher energy levels. if the energy gap between filled and empty shells corresponds to frequencies of visible light then the molecule appears coloured. the colour will be complementary to the light absorbed
48
how do you make a aldehyde from a primary alcohol?
gently heat alcohol with potassium dichromate and distil the aldehyde out
49
how do you make a carboxylic acid from a primary alcohol?
heat with acidified potassium dichromat past the point of aldehyde until reaching COOH
50
how do you make a ketone from a secondary alcohol?
reflux with oxidising agent
51
what is Fehling's solution?
a blue solution of complexed copper (II) ions dissolved in NaOH.
52
how is the Fehling's test used to identify an aldehyde?
1. add 2cm3 of Fehling's soln to test tube
2. add 5 drops of sample to tube
3. warm in hot water bath for 3 mins
4. brick red ppt forms for positive result
53
how do you make Tollens' Reagent?
1. put 2cm3 of 0.1moldm3 silver nitrate soln in test tube
2. add drops of dilute NaOH and a light brown ppt forms
3. add drops of dilute ammonia solution until ppt dissolves
54
how is Tollens' reagent used to identify a aldehyde?
1. make Tollens reagent
2. add drops of sample into tollens in test tube
3. warm in water bath
4. silver mirror forms if aldehyde present
55
how is Tollens' reagent used to identify a ketone?
1. make Tollens reagent
2. add drops of sample into tollens in test tube
3. warm in water bath
4. nothing happens if ketone present
56
how is the Fehling's test used to identify an ketone?
1. add 2cm3 of Fehling's soln to test tube
2. add 5 drops of sample to tube
3. warm in hot water bath for 3 mins
4. nothing happens if a ketone is present
57
name the mechanism in which cyanide reacts with an aldehyde or ketone
nucleophilic addition
58
what is an addition reaction?
two molecules join together to form a single product. involves breaking a double bond
59
what functional groups undergo addition reactions?
alkenes, ketones and aldehydes
60
what is an elimination reaction?
involves removing a functional group which is released as part of a small molecule. often a double bond forms
61
what functional groups undergo elimination reactions?
- X
-OH
62
what is a substitution reaction?
a functional group on a molecule is swapped for a new one
63
what functional groups undergo elimination reactions?
- X
- OH
phenol ring
64
what is a hydrolysis reaction?
water is used too split apart a molecule creating two smaller ones
65
what functional groups undergo hydrolysis?
esters
amides
66
what is an oxidation reaction?
oxidation is a loss of electrons. can involve gaining a oxygen atom or losing a hydrogen atom
67
what is a reduction reaction?
reduction is a gain of electrons. involves gaining a hydrogen atom or losing an oxygen
68
how do you test for an alkene?
1. add 2cm3 of sample to test tube
2. add 2cm3 bromine water to sample
3. shake tube
4. if alkene present bromine water will be decolourised
69
how do you test for a primary alcohol?
1. add 10 drops of alcohol to 2cm3 acidified potassium dichromate soln in test tube
2. warm the mixture in hot water bath
3. orange soln turns green (aldehyde has formed)
70
how do you test for a secondary alcohol?
1. add 10 drops of alcohol to 2cm3 acidified potassium dichromate soln in test tube
2. warm the mixture in hot water bath
3. orange soln turns green (ketone has formed)
71
how do you test for a tertiary alcohol?
1. add 10 drops of alcohol to 2cm3 acidified potassium dichromate soln in test tube
2. warm the mixture in hot water bath
3.nothing happens if tertiary
72
when a primary/secondary alcohol is oxidised by acidified potassium dichromate, what is the colour change caused by?
the orange dichromate ion (CrO7^2-) being reduced to the green chromium (III) ion (Cr^3+)
73
how do you test to distinguish a primary alcohol from a secondary alcohol?
1. add excess alcohol to 2cm3 of acidified potassium dichromate in round bottomed flask
2. connect to a fractionating column and a condenser
3. heat the alcohol will be distilled off immediately
4. perform an aldehyde test
5. if aldehyde present you started with primary and if ketone you started with secondary
74
give the reaction conditions and reagents for:
primary amine --> N-substituted amide
acyl chloride
75
give the reaction conditions and reagents for:
bromoalkane --> primary amine
NH3
reflux
76
give the reaction conditions and reagents for:
alkane --> bromoalkane
Br2
UV light
77
give the reaction conditions and reagents for:
alkene --> alkane
Ni catalyst
150 degrees & high pressure
78
give the reaction conditions and reagents for:
alkene --> dibromoalkane
Br2
20 degrees
79
give the reaction conditions and reagents for:
secondary bromoalkane --> secondary alcohol
NaOH
reflux
80
give the reaction conditions and reagents for:
primary bromoalkane --> primary alcohol
NaOH
reflux
81
give the reaction conditions and reagents for:
primary alcohol --> alkene
conc. H2SO4
170 degrees and reflux
82
give the reaction conditions and reagents for:
alkene --> primary alcohol
H2SO4 catalyst
cold H2O or H3PO4 catalyst
steam and 300 degrees
83
give the reaction conditions and reagents for:
primary alcohol --> aldehyde
K2Cr2O7
H2SO4
heat then distill
84
give the reaction conditions and reagents for:
secondary alcohol --> ketone
K2Cr2O7
H2SO4
reflux
85
give the reaction conditions and reagents for:
ketone --> cyanohydrin
HCN
86
give the reaction conditions and reagents for:
aldehyde --> cyanohydrin
HCN
87
give the reaction conditions and reagents for:
aldehyde --> carboxylic acid
K2Cr2O7
H2SO4
reflux
88
give the reaction conditions and reagents for:
primary amide --> carboxylic acid
H+ (aq)
heat
89
give the reaction conditions and reagents for:
acyl chloride --> ester
alcohol
90
give the reaction conditions and reagents for:
ester --> carboxylic acid
H+
reflux
91
give the reaction conditions and reagents for:
carboxylic acid --> ester
alcohol
H+ catalyst
reflux
92
give the reaction conditions and reagents for:
phenol --> sodium phenoxide
NaOH
20 degrees
93
give the reaction conditions and reagents for:
phenol --> phenyl ethanoate
CH3COCl
20 degrees
94
give the reaction conditions and reagents for:
aminobenzene --> benzenediazonium chloride
HNO2/HCl
below 5 degrees
95
give the reaction conditions and reagents for:
benzenediazonium chloride --> yellow/orange azo compound
phenol
NaOH
below 5 degrees
96
give the reaction conditions and reagents for:
benzene --> nitrobenzene
(NITRATION)
H2SO4
HNO3
55 degrees
97
give the reaction conditions and reagents for:
sulfonation of benzene
fuming H2SO4
40 degrees
98
give the reaction conditions and reagents for:
acylation of benzene
RCOCl
AlCl3 catalyst
reflux
99
give the reaction conditions and reagents for:
benzene --> chlorobenzene
(CHLORINATION)
Cl2
AlCl3 catalyst
warm
100
give the reaction conditions and reagents for:
alkylation of benzene
RCl
AlCl3 catalyst
reflux
101
what is the structure of a fatty acid?
long hydrocarbon chain with carboxylic acid group at the end
102
what can you do to distinguish between a saturated and unsaturated fatty acid?
add bromine water
saturated - stays orange
unsaturated - turns colourless
103
triglycerides are triesters of...
glycerol and fatty acids
104
how is a triglyceride made?
each glycerol molecule loses and 3 OH and each of the 3 fatty acids loses a H to from an ester bond between molecules.
105
in what type of reaction is a triglyceride made?
condensation
106
what is the mobile phase in chromatography?
where the molecules can move. always liquid or gas
107
what is the stationary phase in chromatography?
where the molecules cannot move. must be solid or liquid.
108
what property of each component of a molecule in a mixture tested in GLC determines how long it spends dissolved in the stationary phase and how long it spends moving along the tube in the mobile phase?
the solubility
109
the time taken to reach the detector in GLC is called...
the retention time
110
GLC produces...
chromatograms
111
on a GLC chromatogram the area under each is proportional to the...
relative amount of each substance in the original mixture
112
An azo dye has an extended delocalised system. Describe the bonding occurring in a delocalised system and explain why this leads to organic molecules being coloured.
4 marks
1. delocalisation of electrons
2. split into different electronic energy levels
3. can absorb coloured light
4. complimentary light is transmitted
113
give one property of a dye that could be altered if NO2 groups are added to the molecule
its colour
114
give one property of a dye that might be affected by the attachment of sulfonate (SO3-) groups
its solubility
115
state an important property of the carrier gas in gas liquid chromatograohy
1 mark
it is inert
116
what does the column in gas liquid chromatography consist of
2 marks
1. high boiling point
2. porous support
117
suggest a method to identify compounds after they emerge the gas liquid chromatography
1 mark
mass spectrometry
118
describe how the delocalised electrons are arranged in the benzene structure
2 marks
1. the p orbitals combine to form a deloclaised ring
2. above and below the benzene ring
119
benzene and ethene each undergo electrophilic reactions
state how these reactions differ
1 mark
benzene has electrophilic substitution
and ethene has electrophilic addition
120
explain the bond angle in water
3 marks
1. four areas of electron density
2. repel as far a part as possible from each other
3. two lone pairs repel more than bonding pairs
