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A-Level Chemistry > Last Bit of Yr13!!! > Flashcards

Last Bit of Yr13!!! Flashcards

1
Q

Which are the two ways you can form nitriles?

A

From aldehydes + ketones

From haloalkanes

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2
Q

What are the reagents needed for the formation of nitriles from aldehydes + ketones?

A

React aldehyde/ketone with H2SO4 + NaCN

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3
Q

What is the mechanism for forming nitriles from aldehydes + ketones?

A

Nucleophilic addition

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4
Q

What is the equation for forming nitriles from aldehydes + ketones?

A

CH3CH2CH2CHO + HCN —-> CH3CH2CH2CH(OH)CN

H2SO4/NaCN go across the arrow

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5
Q

Name CH3CH2CH2CH(OH)CN

A

2 - hydroxy pentane nitrile

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6
Q

What is the nucleophile in forming nitriles from aldehydes + ketones?

A

CN-

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7
Q

What are the reagents needed for formation of nitriles from haloalkanes?

A

React haloalkane with NaCN or KCN in ethanol

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8
Q

What is the mechanism for forming nitriles from haloalkanes?

A

Nucelophillic substitution

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9
Q

What is the equation for forming nitriles from haloalkanes?

A

CH3CH2Cl + NaCN —-> CH3CH2CH2CN + NaCl

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10
Q

Name CH3CH2CH2CN

A

Butane nitrile

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11
Q

What is the nucleophile in forming nitriles from haloalkanes?

A

CN-

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12
Q

Can you use nitriles as intermediates to form other organic substances?

A

YES

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13
Q

What happens if you reduce a nitrile?

A

Form amine

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14
Q

What happens if you hydrolyse a nitrile?

A

Form carboxylic acid

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15
Q

What are the reagents for reducing a nitrile?

A

H2

Ni catalyst

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16
Q

What is the equation for reducing a nitrile?

A

CH3CH2CN + 2H2 —-> CH3CH2CH2H2

Ni across arrow

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17
Q

Name CH3CH2CH2H2

A

Propylamine

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18
Q

What are the reagents for hydrolysis of nitrile?

A

Heat

Dilute aqueous HCl

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19
Q

What is the equation for hydrolysis of nitrile?

A

CH3CH2CN + 2H2O + HCl —-> CH3CH2COOH + NH4Cl

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20
Q

Name CH3CH2COOH

A

Propanoic acid

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21
Q

Name NH4Cl

A

Ammonium chloride

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22
Q

What are the six steps for synthesising aspirin?

A 
Prepare organic substance
Prepare aspirin
Filter under reduced pressure
Recrystallisation 
Filter under reduced pressure again 
Determine melting point of aspirin
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23
Q

What happens in “Prepare organic substance”?

A

Add NaOH to oil of wintergreen
Reflux - 30 mins
Leave to cool
Add HCl to neutralise

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24
Q

What happens in “Prepare aspirin”?

A

React 2-hydroxy benzoic acid (salicylic acid) with ethanoic acid
Add drops of conc acid
Warm mixture in water bath till solid dissolves

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25
Q

What happens in “Filter under reduced pressure”?

A

Cool mixture

Filer under pressure using Buchner funnel

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26
Q

What happens in “Recrystallisation”?

A

Slowly add minimum amount of hot solvent (ethanol) to impure aspirin
Sample will dissolve
Cool mixture to allow recrystallisation

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27
Q

What happens in “Filter under reduced pressure again”?

A

Filter under reduced pressure using Buchner funnel

Wash purified aspirin in cold water

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28
Q

Why do you wash aspirin in cold water?

A

As it isn’t very soluble in cold water

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29
Q

What happens in “Determine melting point of aspirin”?

A

Use melting point apparatus
Insert sample into melting point tube
Slowly increase temperature
Record the range over when it starts to melt
Impurities = lower melting point = wider range

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30
Q

What is an alternative method for “Determine melting point of aspirin”?

A

Set up Thiele Tube
Attach capillary tube to thermometer using rubber band
Use micro-burner to slowly heat side arm of Thiele Tube
When solid starts to melt remove heat + record temperature

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31
Q

What are the three types of chromatography?

A

Paper
TLC
Gas

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32
Q

What is the stationary phase in paper?

A

Paper

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33
Q

What is the mobile phase in paper?

A

Solvent

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34
Q

What does it mean if the dot remains under the line?

A

Not soluble in that solvent

35
Q

Where should the amount of solvent be up to?

A

Below pencil line

36
Q

How do you calculate Rf value?

A 
         Solvent front
37
Q

What are the problems with paper?

A

Components can have similar Rf values

Unknown substances appear

38
Q

What is the stationary phase in TLC?

A

Silica coated on piece of plastic

39
Q

What is the mobile phase in TLC?

40
Q

What is the method for TLC?

A

Base line drawn in pencil + place dots along line
Plate places in beaker of solvent (below pencil line)
Lid placed on to ensure atmosphere of tank saturated wit volatile solvent
As solvent moves up mixture separates into components
Solvent reaches top of plate + plate removed
Solvent front noted + solvent left to evaporate

41
Q

What happens if the substance is colourless?

A

Use UV light

Chemically

42
Q

How does it work if you use UV light?

A

Stationary phase has chemical that will fluoresce under UV light
Spots go white

43
Q

How does it work if you do it chemically?

Ninhydrin

A

Ninhydrin sprayed on = amino acids go brown/purple colour

44
Q

How does it work if you do it chemically?

Iodine crystals

A

Put dried plate in beaker of iodine crystals + put lid on

Spots turn brown

45
Q

How does TLC acc work?

A

Silica gel form silicon dioxide
Surface of silica = very polar
So can form H bonds with OH group
+ London forces + permeant dipole-dipole

46
Q

What is adsorption?

A

The adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface

47
Q

How does TLC acc work?

Part 2

A

Solid stationary phase = pigment adsorbed onto surface of solid particles
Relative forces of attraction between stationary phase, mobile phase + pigment = separation

48
Q

What does it mean if pigment has weak forces of adsorption?

A

Less polar = move further up

49
Q

What does it mean if pigment has strong forces of adsorption?

A

More polar = moves less

50
Q

What are the control measures of TLC?

A

Same solvent
Same temperature
Same stationary phase

51
Q

What is gas - liquid chromatography?

A

Long column filled with liquid compounds

Sample vaporised + pushed through column by inert carrier gas

52
Q

What inert gas is often used in GLC?

53
Q

Why is GLC kept in an oven?

A

To control temperature

54
Q

What does GLC work on?

A

Relative solubility compared to stationary phase

55
Q

What is the stationary phase of GLC?

A

Liquid coated on tubes

56
Q

What does GLC show because it works on solubility compared to stationary phase?

A

Different compounds will travel at different speeds

= different boiling points + temperature inside column

57
Q

What is retention time?

A

The length of time a compound remains in a column

58
Q

How do you calculate retention time?

A

Time taken from sample injected until max height for that compound

59
Q

What does each peak in GLC correspond to?

A

Different compounds

60
Q

What must you do after you calculate retention time?

A

Compare to known database

61
Q

Which compound would come out last in GLC?

A

The most similar to stationary phase

62
Q

Which compound would come out first in GLC?

A

The one that isn’t similar but has the least no. of H bonds

= more H bonds = stronger attraction with stationary phase

63
Q

How do you calculate the composition of a mixture in GLC?

A

Area of triangle for peak = 0.5 X base X height
Work out total area = add them together
Area of peak/ total area X 100

64
Q

How does mass spectroscopy work?

A

Sample injected
Vaporised in heated vacuum
Gas vapour bombarded with high energy e- forms positive ions in ionisation chamber
+ions accelerated
Ions travel through magnetic filed in drift region
Time taken for ions to reach detector is measured

65
Q

What does it mean if the ions are heavier?

A

Move more slowly = take longer to reach detector

66
Q

What does M/Z of molecule equal + why?

A

Mr

As weight of e- is negligible

67
Q

What does the M+ peak equal?

A

The total Mr for the compound

68
Q

What is abundance?

A

The relative amount of ions in the spectra - usually given as a percentage

69
Q

What is the equation for mass spectroscopy?

A

M (g) —-> M+ (g) + e-

70
Q

Outline how a mass spectrometer would show the presence of Fe

A

M/Z value around 56

71
Q

Why use the word “around”?

A

Abundance of isotopes

72
Q

Outline how the mass spectrum would show how many different isotopes of sulphur were present

A

Count no. of M/Z peaks around 32

73
Q

Relative atomic mass of sulphur found on Mars is different from relative atomic mass of S found on Earth. Why?

A

Different isotopic abundances

74
Q

What can excess ionisation do when it is transferred to the molecular ion?

A

Can cause it to fragment

75
Q

What happens when it fragments?

A

Produces smaller positive ion + radical
Smaller positive ion detected
Fragment ions can be broken down further

76
Q

What is the M+1 peak caused by?

A

Carbon - 13 isotope

77
Q

What is the Mr of CH3+?

78
Q

What is the Mr of C2H5+?

79
Q

What is the Mr of C3H7+?

80
Q

What is the Mr of C4H9+?

81
Q

What is the Mr of OH+?

82
Q

What are the example of CH3CH2OH splitting?

A

CH3CH2OH (g) —-> CH3CH2OH+ (g) + e-
CH3CH2OH+ (g) —-> CH2OH+ (g) + .CH3
CH3CH2OH+ (g) —-> CH3+ (g) + .CH2OH
CH3CH2OH+ (g) —-> CH3CH2+ (g) + .OH

83
Q

Whys is GLC not suitable technique for analysing mixture of dyes?

A

Because dyes not easily vaporised

A-Level Chemistry (26 decks)

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