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A Level Chemistry > Colour by Design > Flashcards

Colour by Design Flashcards

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1
Q

what is the formula for benzene?

A

C6H6

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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

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3
Q

why was Kekules structure wrong?

A

all the C-C bonds in benzene are the same length

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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

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5
Q

ethene + bromine is an example of what kind of reaction?

A

electrophilic addition

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6
Q

in the reaction ethene + bromine what is produced?

A

1,2- di bromoethane

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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

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8
Q

when you warm benzene with concentrated nitric and sulfuric acid you get….

A

nitrobenzene

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9
Q

halogen carriers help to make good….

A

electrophiles

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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

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11
Q

what is a carbocation?

A

an organic ion with a positively charged carbon atom

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12
Q

halogen carriers can be put an alkyl group on…

A

benzene

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13
Q

how can methylbenzene be made?

A
  1. carbocation formed from chloroalkane and AlCl3
  2. then the carbocation reacts with benzene via electrophilic substitution
  3. the halogen carrier gets regenerated when AlCl4- reacts with the H+ ion comes off the benzene
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14
Q

what type of reaction is the method to put an alkyl group on a benzene ring?

A

friedel-crafts alkylation

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15
Q

the general reaction when an alkyl group is put on a benzene is…

A

C6H6 + RCl –> C6H5R + HCl
catalyst - AlCl3
reflux

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16
Q

what conditions are needed to put an alkyl group on a benzene?

A

reflux

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17
Q

halogen carriers help halogens….

A

substitute onto a benzene ring

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18
Q

how do halogen carriers help halogens substitute into the benzene ring?

A
  1. halogen carriers polarise halogen molecules
  2. the +vely charges end of the halogen acts as an electrophile and reacts with the benzene ring
  3. electrophilic substitution reaction
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19
Q

what type of reaction is halogen substituting onto a benzene ring?

A

electrophilic substitution

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20
Q

halogen carriers can put acyl groups…

A

on benzene

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21
Q

what is the method for substituting a acyl group on a benzene?

A
  1. acylium ion is formed from acyl chloride and AlCl3
  2. the acylium ion acts as the electrophile and goes to react with benzene
  3. AlCl3 then gets regenerated
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22
Q

when an acyl group is substituted for a H atom on benzene what conditions are needed?

A

reflux

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23
Q

azo dyes are man made dyes that contain the azo group. the azo group is….

A

-N=N-

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24
Q

in azo dyes the azo group links…

A

two aromatic groups

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25
Q

why does delocalisation extend across the whole dye molecule?

A

it contains two aromatic groups making it very stable. the azo group becomes part of the delocalised electron system

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26
Q

what type of reaction makes an azo dye?

A

a coupling reaction

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27
Q

what are the 2 steps to making an azo dye?

A
  1. react phenylamine with nitrous acid to make a diazonium salt
  2. make the azo dye by coupling the diazonium salt with phenol
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28
Q

how is a diazonium salt made?

A
  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
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29
Q

when a diazonium salt is made why does it have to be carried out below 5 degrees?

A

to prevents a phenol forming instead

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30
Q

how is an azo dye made by coupling the diazonium salt with a phenol?

A
  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
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31
Q

what does colourfast mean?

A

a dye cant wash out too easily or fade in the light

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32
Q

which part of a dye binds to the fabric?

A

its functional group

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33
Q

dyes that contain the amine group bind best to what material?

A

cotton rayon and linen

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34
Q

why do dyes with amine groups bond to cotton, rayon and nylon best?

A

NH2 form H bonds with OH groups. there are many OH groups groups in these materials.

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35
Q

are dyes with the functional group NH2 bound to the material strong? why?

A

no
hydrogen bonds aren’t strong enough

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36
Q

dyes that contain acidic groups bind best to what materials?

A

wool, silk and nylon

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37
Q

how do dyes with acidic groups join to wool, silk and nylon?

A

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

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38
Q

dyes that contain ionic salt groups bind best to what materials?

A

wool, silk and nylon

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39
Q

how do dyes with ionic salt groups bind to wool, silk and nylon?

A

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

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40
Q

the most permanent type of dye is….

A

fibre reactive dyes

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41
Q

why are fibre reactive dyes the most permanent type of dye?

A

they have a functional group that will react with the OH or NH group in the fibre, forming strong covalent bonds

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42
Q

what part of a dye molecule gives the dye its colour?

A

the chromophore

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43
Q

when light hits a chromophore how is light seen?

A

certain wavelengths are absorbed by electrons in the chromophore. visible wavelengths not absorbed will be seen as a particular colour

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44
Q

how does modifying the chromophore change the colour of a molecule?

A

it will change the frequency of light it absorbs

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45
Q

when functional groups conatining O and N are added to the chromophore why does the molecules colour change?

A

the lone pair of electrons becomes part of the delocalised system responsible for absorbing light

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46
Q

what groups are sometimes added to dyes to make them more water soluble?

A

ionic groups

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47
Q

how does light appear colored?

A

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

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48
Q

how do you make a aldehyde from a primary alcohol?

A

gently heat alcohol with potassium dichromate and distil the aldehyde out

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49
Q

how do you make a carboxylic acid from a primary alcohol?

A

heat with acidified potassium dichromat past the point of aldehyde until reaching COOH

50
Q

how do you make a ketone from a secondary alcohol?

A

reflux with oxidising agent

51
Q

what is Fehling’s solution?

A

a blue solution of complexed copper (II) ions dissolved in NaOH.

52
Q

how is the Fehling’s test used to identify an aldehyde?

A
  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
Q

how do you make Tollens’ Reagent?

A
  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
Q

how is Tollens’ reagent used to identify a aldehyde?

A
  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
Q

how is Tollens’ reagent used to identify a ketone?

A
  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
Q

how is the Fehling’s test used to identify an ketone?

A
  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
Q

name the mechanism in which cyanide reacts with an aldehyde or ketone

A

nucleophilic addition

58
Q

what is an addition reaction?

A

two molecules join together to form a single product. involves breaking a double bond

59
Q

what functional groups undergo addition reactions?

A

alkenes, ketones and aldehydes

60
Q

what is an elimination reaction?

A

involves removing a functional group which is released as part of a small molecule. often a double bond forms

61
Q

what functional groups undergo elimination reactions?

A
  • X
    -OH
62
Q

what is a substitution reaction?

A

a functional group on a molecule is swapped for a new one

63
Q

what functional groups undergo elimination reactions?

A
  • X
  • OH
    phenol ring
64
Q

what is a hydrolysis reaction?

A

water is used too split apart a molecule creating two smaller ones

65
Q

what functional groups undergo hydrolysis?

A

esters
amides

66
Q

what is an oxidation reaction?

A

oxidation is a loss of electrons. can involve gaining a oxygen atom or losing a hydrogen atom

67
Q

what is a reduction reaction?

A

reduction is a gain of electrons. involves gaining a hydrogen atom or losing an oxygen

68
Q

how do you test for an alkene?

A
  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
Q

how do you test for a primary alcohol?

A
  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
Q

how do you test for a secondary alcohol?

A
  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
Q

how do you test for a tertiary alcohol?

A
  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
Q

when a primary/secondary alcohol is oxidised by acidified potassium dichromate, what is the colour change caused by?

A

the orange dichromate ion (CrO7^2-) being reduced to the green chromium (III) ion (Cr^3+)

73
Q

how do you test to distinguish a primary alcohol from a secondary alcohol?

A
  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
Q

give the reaction conditions and reagents for:
primary amine –> N-substituted amide

A

acyl chloride

75
Q

give the reaction conditions and reagents for:
bromoalkane –> primary amine

A

NH3
reflux

76
Q

give the reaction conditions and reagents for:
alkane –> bromoalkane

A

Br2
UV light

77
Q

give the reaction conditions and reagents for:
alkene –> alkane

A

Ni catalyst
150 degrees & high pressure

78
Q

give the reaction conditions and reagents for:
alkene –> dibromoalkane

A

Br2
20 degrees

79
Q

give the reaction conditions and reagents for:
secondary bromoalkane –> secondary alcohol

A

NaOH
reflux

80
Q

give the reaction conditions and reagents for:
primary bromoalkane –> primary alcohol

A

NaOH
reflux

81
Q

give the reaction conditions and reagents for:
primary alcohol –> alkene

A

conc. H2SO4
170 degrees and reflux

82
Q

give the reaction conditions and reagents for:
alkene –> primary alcohol

A

H2SO4 catalyst
cold H2O or H3PO4 catalyst
steam and 300 degrees

83
Q

give the reaction conditions and reagents for:
primary alcohol –> aldehyde

A

K2Cr2O7
H2SO4
heat then distill

84
Q

give the reaction conditions and reagents for:
secondary alcohol –> ketone

A

K2Cr2O7
H2SO4
reflux

85
Q

give the reaction conditions and reagents for:
ketone –> cyanohydrin

A

HCN

86
Q

give the reaction conditions and reagents for:
aldehyde –> cyanohydrin

A

HCN

87
Q

give the reaction conditions and reagents for:
aldehyde –> carboxylic acid

A

K2Cr2O7
H2SO4
reflux

88
Q

give the reaction conditions and reagents for:
primary amide –> carboxylic acid

A

H+ (aq)
heat

89
Q

give the reaction conditions and reagents for:
acyl chloride –> ester

A

alcohol

90
Q

give the reaction conditions and reagents for:
ester –> carboxylic acid

A

H+
reflux

91
Q

give the reaction conditions and reagents for:
carboxylic acid –> ester

A

alcohol
H+ catalyst
reflux

92
Q

give the reaction conditions and reagents for:
phenol –> sodium phenoxide

A

NaOH
20 degrees

93
Q

give the reaction conditions and reagents for:
phenol –> phenyl ethanoate

A

CH3COCl
20 degrees

94
Q

give the reaction conditions and reagents for:
aminobenzene –> benzenediazonium chloride

A

HNO2/HCl
below 5 degrees

95
Q

give the reaction conditions and reagents for:
benzenediazonium chloride –> yellow/orange azo compound

A

phenol
NaOH
below 5 degrees

96
Q

give the reaction conditions and reagents for:
benzene –> nitrobenzene
(NITRATION)

A

H2SO4
HNO3
55 degrees

97
Q

give the reaction conditions and reagents for:
sulfonation of benzene

A

fuming H2SO4
40 degrees

98
Q

give the reaction conditions and reagents for:
acylation of benzene

A

RCOCl
AlCl3 catalyst
reflux

99
Q

give the reaction conditions and reagents for:
benzene –> chlorobenzene
(CHLORINATION)

A

Cl2
AlCl3 catalyst
warm

100
Q

give the reaction conditions and reagents for:
alkylation of benzene

A

RCl
AlCl3 catalyst
reflux

101
Q

what is the structure of a fatty acid?

A

long hydrocarbon chain with carboxylic acid group at the end

102
Q

what can you do to distinguish between a saturated and unsaturated fatty acid?

A

add bromine water
saturated - stays orange
unsaturated - turns colourless

103
Q

triglycerides are triesters of…

A

glycerol and fatty acids

104
Q

how is a triglyceride made?

A

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
Q

in what type of reaction is a triglyceride made?

A

condensation

106
Q

what is the mobile phase in chromatography?

A

where the molecules can move. always liquid or gas

107
Q

what is the stationary phase in chromatography?

A

where the molecules cannot move. must be solid or liquid.

108
Q

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?

A

the solubility

109
Q

the time taken to reach the detector in GLC is called…

A

the retention time

110
Q

GLC produces…

A

chromatograms

111
Q

on a GLC chromatogram the area under each is proportional to the…

A

relative amount of each substance in the original mixture

112
Q

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

A
  1. delocalisation of electrons
  2. split into different electronic energy levels
  3. can absorb coloured light
  4. complimentary light is transmitted
113
Q

give one property of a dye that could be altered if NO2 groups are added to the molecule

A

its colour

114
Q

give one property of a dye that might be affected by the attachment of sulfonate (SO3-) groups

A

its solubility

115
Q

state an important property of the carrier gas in gas liquid chromatograohy

1 mark

A

it is inert

116
Q

what does the column in gas liquid chromatography consist of

2 marks

A
  1. high boiling point
  2. porous support
117
Q

suggest a method to identify compounds after they emerge the gas liquid chromatography

1 mark

A

mass spectrometry

118
Q

describe how the delocalised electrons are arranged in the benzene structure

2 marks

A
  1. the p orbitals combine to form a deloclaised ring
  2. above and below the benzene ring
119
Q

benzene and ethene each undergo electrophilic reactions

state how these reactions differ

1 mark

A

benzene has electrophilic substitution
and ethene has electrophilic addition

120
Q

explain the bond angle in water

3 marks

A
  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

A Level Chemistry (12 decks)

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