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N Chemistry A Level > Topic 6 Organic Chemistry > Flashcards

Topic 6 Organic Chemistry Flashcards

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1
Q

Why are alcohols ‘good’ fuels?

A
  • easy to transport
  • easy to store
  • very exothermic combustion (completely)
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2
Q

How can ethanol be made?

A
  • fermentation
  • from ethene (+ steam using H3PO4 catalyst)
  • SN of halogenoalkane
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3
Q

What is halogenation?

A

Replacing Hydrogen with halogen
E.g. Making halogenoalkane from alcohol

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4
Q

How to test for Alkene?

A

Bromine water from orange to colourless

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5
Q

What is stereoisomerism?

A

Molecules that have the same molecular formula and the same structural formula, but have different 3D shape

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6
Q

What isomerism can Alkenes have?

A

Geometric isomerism

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7
Q

Why can some alkenes have geometric isomerism?

A

Because of the C=C bond, they must have 2 diff groups bonded to them

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8
Q

What is the E/Z nomenclature system?

A

Zame Zide of high priority groups (w highest number of atomic num)
E is opposite sides

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9
Q

Combustion of alkenes
Compare result with corresponding alkane

A

Alkene + oxygen -> water + carbon dioxide
Alkenes are more likely to burn with sootier flames than corresponding alkane
(Bcs of lower C:H ratio)

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10
Q

What is an addition reaction?

A

2+ reactants in 1 product

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11
Q

What is an electrophile?

A

Small species that can accept a pair of electrons / attracted to area of high e- density
Either has positive charge or δ+

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12
Q

Why do alkenes react with electrophiles?

A

Because alkenes have a pair of e- in a π bond (of C=C)
Has High electron density
Which can form a bond to electrophile

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13
Q

Why will alkenes readily react in addition reactions?

A

π bonds are weak and sticks out

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14
Q

What is hydrogenation?

A

Adding hydrogen to an alkene, forming corresponding alkane

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15
Q

What condition and reactant does hydrogenation must take place in?
(Alkene -> alkane)

A

Add Hydrogen
Ni catalyst 150 C
Or
Pt catalyst RTP

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16
Q

Why is hydrogenation an important reaction?

A

So margarine can be made from oils

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17
Q

Alkene + Halogen -> ?

A

Dihalogenoalkane

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18
Q

What conditions needed to make dihalogenoalkane from Alkene and halogen?

A

Mix and shake

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19
Q

Alkene + hydrogen halide -> ?

A

Halogenoalkane

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20
Q

What is Markovnikoff’s rule?

A

Hydrogen will be more attracted to the C atom with most H attached to it already (in a C=C bond)

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21
Q

Alkenes + steam -> ?

A

Alcohol

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22
Q

Why does Markovnikoff’s rule happen?

A

The greater number of alkyl group, the most stable the carbocation is most likely to form

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23
Q

What carbocation is least stable?

A

1° primary

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24
Q

What carbocation is most stable?

A

3 °

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25
Q

What conditions are required for alkenes + steam to form alcohol?

A

H3PO4 phosphoric acid
at 300°C
60 atm

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26
Q

Alkene + Br2 (aq) ->

A

Bromoalcohol !!!

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27
Q

What is needed to oxidise alkenes into diols?

A

H2SO4 and KMnO4
Sulfuric acid and potassium manganate

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28
Q

Alkene + [O] + H2O -> ?

A

Diol

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29
Q

What reagent and conditions are needed to make Diol from oxidising alkene?

A

KMnO3
H2SO4 heat under reflux

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30
Q

What colour is potassium manganate

A

Purple

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31
Q

Why can alkenes polymerise?

A

Bcs of π bonds that break and σ bonds form between C and monomer units

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32
Q

What reaction is polymerisation? And what is added?

A

Free radical addition
add free radical initiator

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33
Q

What is the general equation for cycloalkane?

A

CnH2n

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34
Q

What are the 4 steps of free radical substitution?

A

Initiation
Propagation 1
Propagation 2
Termination

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35
Q

What is the initiator for halogens?

A

UV light

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36
Q

how to convert halogenoalkane to alkene? what conditions and reagent required?

A

conc KOH or NaOH
ethanol and heat

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37
Q

what reagent and condition needed to form nitrile from halogenoalkane? Why is it useful for organic chemistry?

A

KCN / NaCN , heat under reflux
increases C chain length

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38
Q

What is a reagent?

A

Reactant’s Name on the bottle

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39
Q

What is the reagent to oxidise alcohol?

A

Potassium or Sodium
Dichromate Cr2O7^2-
Orange to green if positive
+ H2SO4

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40
Q

What does PCl5 test for

A

-OH group
Alcohol or carboxylic acid
(Also chlorination)

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41
Q

How to test for primary secondary or tertiary alcohol?

A

Oxidising
- reflux it
See what products it makes

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42
Q

How to eliminate/dehydrate alcohol? What does it make?

A

Use conc. sulfuric H2SO4 or phosphoric acid H3PO4
Make alkenes and water

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43
Q

What are 2 methods of chlorination?

A

Add conc HCl
Or
Add PCl5

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44
Q

What is PCl5 used for? What does positive result look like?

A

Test for -OH groups (water, alcohol and carboxylic acid)
White misty fumes

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45
Q

What are 2 methods of bromination?

A

50% conc H2SO4 +NaBr making HBr + NaHSO4
Alcohol + HBr -> Bromoalkane + water
Or
Add PBr3

46
Q

Why 50% conc H2SO4 for bromination?

A

Trying to make HBr, prevent redox reaction forming other unwanted products

47
Q

How to iodination to make iodoalkane?

A

Reagents
- damp red phosphorus
- iodine
P + 1.5 I2 -> PI3
Add this to alcohol to make iodoalkane

48
Q

What colour is dichromate?

A

Orange

49
Q

What is a reagent?

A

Name on the bottle

50
Q

2 types of reagents needed to oxidise alcohol?

A

K/Na dichromate (Cr2O7 2-)
Sulfuric acid H2SO4 (H+)

51
Q

What is formed when oxidising primary alcohols using distillation?

A

Aldehyde + water formed

52
Q

What is formed when oxidising primary alcohol via reflux?

A

Carboxylic acid and water formed

53
Q

How is oxidation written in organic chemistry?

A

[O]

54
Q

How to oxidise secondary alcohols? What is produced?

A

Reflux or distill
Ketone + water produced

55
Q

What is formed when refluxing / distilling tertiary alcohol?

A

No reaction
Since no H can be removed
So cannot be oxidised

56
Q

What’s a carbonyl?

A

Aldehyde + ketone
=O bond in middle of C chain

57
Q

What colour is manganate?

A

Purple

58
Q

What does MnO4- + H2SO4 oxidise? What colour does it turn from and to?

A

Alkenes, alcohols and aldehydes
Purple to colourless

59
Q

What does Cr2O7 2- + H2SO4 oxidise? What colour does it change from and to?

A

Alkenes, alcohols and aldehydes
Orange to green

60
Q

How to dehydrate alcohols? (What reagent is used?)

A

Conc H3PO4
phosphoric acid
(OR conc sulfuric acid H2SO4)

61
Q

What is formed from dehydrating an alcohol?

A

Alkene + water

62
Q

Does miscibility/solubility increase or decrease as alcohol chain length increases? Why?

A

Decreases bcs C:OH ratio decreases
Greater C chain is more non polar, so becomes less soluble (less interaction between OH and water, cannot form H bonds)
Bigger molecules take up more space, more non-polar proportion to polar

63
Q

Does viscosity increase or decrease as alcohol chain length increases?

A

Increase bcs number of OH group increases

64
Q

Does bp increase or decrease as alcohol chain length increases?

A

Increase as more e- means more London forces which takes more energy to break

65
Q

Does corresponding alcohol or alkane have a higher mp/bp?

A

Alcohol is much higher since have more e-s so more London forces
And alcohol have H bonds, alkanes don’t

66
Q

What’s an aldehyde?

A

=O at the end of C chain

67
Q

Halogenoalkane + ammonia (NH3) ->
What conditions needed?

A

-> Amine + HX
AND -> Amine + NH4X
- Excess NH3 (so only get 1 substitution)
- dissolved in ethanol!!
- heat in sealed tube

68
Q

What is the functional group of amine?

A

-NH2

69
Q

Halogenoalkane + OH- (eth) ->

A

Alkene + H2O + X-
(Only if there is adjacent H atom)
Using ethanol solvent, with reagent NaOH or KOH
Heat under reflux

70
Q

Halogenoalkane + OH- (aq) ->
(+ what mechanisms used?)

A

Alcohol + halide
Either SN 1 (3° or 2°)
SN2 (1°)

71
Q

What is a nucleophile?

A

Has lone pair

72
Q

What is a nucleophilic substitution reaction and 2 examples?

A

Attacking δ+ (positive) and replacing the bond with something δ-
SN1 or SN2

73
Q

What do you call CH3CH2CH2(NH2)

A

amino propane

74
Q

What do you call CH3C≡N

A

methane nitrile

75
Q

Ag+ + X- ->
What is it used for?

A

AgX (s)
Precipitate show presence of halides

76
Q

What are the AgX precipitate colours?
What further testing to identify each halide?

A

Chlorine - white (soluble in both dil and conc NH3)
Bromine - cream (only in conc)
Iodine - yellow (neither)

77
Q

What reaction is Halogenoalkane + OH- (eth) ?

A

Elimination (coz C=C is made)
As a base not a nucleophile
Reflux

78
Q

Why does F have the strongest bond enthalpy in G7?

A

Smallest ion
So smallest atomic radius
So stronger attraction

79
Q

What does Fehling’s solution test for? In what conditions?

A

Ketones (stays blue) or aldehydes (turns red)
In warm water bath

80
Q

What’s the difference between cis/trans and E/Z classification?

A

cis/trans must have identical groups attached to diff sides of alkene (at least 2 repeating)
E/Z could have 4 diff groups

81
Q

Devise an experiment to compare rate of Halogenoalkane hydrolysis (6 marks)

A
  • add ethanol as solvent (so it dissolves and reacts with water)
  • fair test (equal volume and temp)
  • add silver nitrate
  • record time taken for ppt to form
  • iodoalkane should be the fastest, chloroalkane slowest - due to bond enthalpies for C-I<C-Br<C-Cl
82
Q

Why is ethanol added for hydrolysis of Halogenoalkane?

A

So reactants are more miscible/soluble

83
Q

Why are test tubes left in 50 C water bath for Halogenoalkane hydrolysis?

A

To allow reactions to equilibriate

84
Q

What is the reagent to make nitriles? What’s the advantage?

A

Potassium cyanide KCN
Increase carbon chain length

85
Q

Why is it heated in a sealed container when making amine from Halogenoalkane? 2 marks

A

Increase RoR
No sealed tube results in loss of ammonia

86
Q

What is the rate of hydrolysis of primary secondary and tertiary Halogenoalkane?

A

3 ° > 2 °> 1 °
Most stable is tertiary carbocation so easier to lose the halide

87
Q

Structural isomer vs stereoisomers?

A

Structural: have the same molecular formula but a different bonding arrangement among the atom
Stereoisomers: have identical molecular formulas and arrangements of atoms. They differ in 3D structure

88
Q

What alcohol cannot be oxidised?

A

Tertiary alcohol
No change in reaction

89
Q

What is a structural isomer? 2 marks

A

Same molecular formula
But different structural formula

90
Q

What is the purpose of condensers when hydrolysing Halogenoalkane?

A

Prevent loss of reactants

91
Q

What is used to test for butan-1-ol and what’s the expected observation?

A

Phosphorus(V)chloride PCl5
White Misty fumes
Because it Has -OH group

92
Q

Why can’t tertiary haloalkanes do SN2?

A

due to steric hinderance

93
Q

Why can’t primary halogenoalkanes do SN1?

A

too unstable

94
Q

What reagent is used to eliminate Halogenoalkane?

A

conc NaOH/KOH
Aka OH- (eth)

95
Q

What is the classification of a Halogenoalkane or alcohols?

A

Primary secondary or tertiary

96
Q

What are 2 chemicals used to make ethanal from ethanol?

A

H2SO4
K2Cr2O7

97
Q

What’s the issue with SO2?

A

Dissovles in raindrops and makes acid rain

98
Q

What is CFC (chlorofluorocarbons)’s properties?

A
  • greenhouse gas
  • damage ozone layer
  • excellent refrigerant
  • inflammable (man inhaled it)
99
Q

Why are the conc H2SO4 and K2Cr2O7 added a drop at a time in the lab process?

A

Control rate of reaction to prevent exothermic reaction from overheating and exploding

100
Q

What is the systematic name of CF2ClBr?

A

bromo chloro difluoro methane

101
Q

Why are halogenoalkanes very good for putting out fires? 2 marks

A
  • non flammable, unreactive
  • v dense so smother and displace O2
102
Q

why are HCFCs better than CFCs?

A

CFCs reach upper atmosphere and react, creating radicals
damage Ozone layer
HCFCs dont reach upper atmosphere bcs less reactive, so no damage to Ozone layer

103
Q

How to differentiate carboxylic acid from aldehyde produced for primary alcohols?

A

Add carbonate (e.g. Na2CO3)
Effervescence since H+ ions react to produce CO2

104
Q

How to separate 2 substances?

A
  • separating funnel
  • simple distillation
  • fractional distillation
  • drying agent to remove water eg calcium chloride
105
Q

How to use separating funnel?

A

You want the top layer
Overrun bottom layer
Repeat a few times
Run upper layer into another flask

106
Q

Why is incineration a bad method for disposal of poly(chloroethene)? 2 marks

A

HCl produced
Very toxic

107
Q

What type of reaction is hydrogenation?

A

Reduction

108
Q

Explain why Markovnikoff’s rule happen

A

More alkyl groups = more electron pushing
So carbocations more likely to form
H attracted to C with more H bonded to it already

109
Q

Are carboxylic acids strong or weak acids?

A

Weak

110
Q

How do chemists limit the problems caused by polymer disposal?

A
  • develop biodegradable polymers
  • remove toxic waste gases caused by incinerating plastics

N Chemistry A Level (21 decks)

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