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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
What happens in "Filter under reduced pressure"?
Cool mixture | Filer under pressure using Buchner funnel
26
What happens in "Recrystallisation"?
Slowly add minimum amount of hot solvent (ethanol) to impure aspirin Sample will dissolve Cool mixture to allow recrystallisation
27
What happens in "Filter under reduced pressure again"?
Filter under reduced pressure using Buchner funnel | Wash purified aspirin in cold water
28
Why do you wash aspirin in cold water?
As it isn't very soluble in cold water
29
What happens in "Determine melting point of aspirin"?
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
30
What is an alternative method for "Determine melting point of aspirin"?
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
31
What are the three types of chromatography?
Paper TLC Gas
32
What is the stationary phase in paper?
Paper
33
What is the mobile phase in paper?
Solvent
34
What does it mean if the dot remains under the line?
Not soluble in that solvent
35
Where should the amount of solvent be up to?
Below pencil line
36
How do you calculate Rf value?
Distance moved by pigment ----------------------------------------- Solvent front
37
What are the problems with paper?
Components can have similar Rf values | Unknown substances appear
38
What is the stationary phase in TLC?
Silica coated on piece of plastic
39
What is the mobile phase in TLC?
Solvent
40
What is the method for TLC?
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
What happens if the substance is colourless?
Use UV light | Chemically
42
How does it work if you use UV light?
Stationary phase has chemical that will fluoresce under UV light Spots go white
43
How does it work if you do it chemically? | Ninhydrin
Ninhydrin sprayed on = amino acids go brown/purple colour
44
How does it work if you do it chemically? | Iodine crystals
Put dried plate in beaker of iodine crystals + put lid on | Spots turn brown
45
How does TLC acc work?
Silica gel form silicon dioxide Surface of silica = very polar So can form H bonds with OH group + London forces + permeant dipole-dipole
46
What is adsorption?
The adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface
47
How does TLC acc work? | Part 2
Solid stationary phase = pigment adsorbed onto surface of solid particles Relative forces of attraction between stationary phase, mobile phase + pigment = separation
48
What does it mean if pigment has weak forces of adsorption?
Less polar = move further up
49
What does it mean if pigment has strong forces of adsorption?
More polar = moves less
50
What are the control measures of TLC?
Same solvent Same temperature Same stationary phase
51
What is gas - liquid chromatography?
Long column filled with liquid compounds | Sample vaporised + pushed through column by inert carrier gas
52
What inert gas is often used in GLC?
N2 or He
53
Why is GLC kept in an oven?
To control temperature
54
What does GLC work on?
Relative solubility compared to stationary phase
55
What is the stationary phase of GLC?
Liquid coated on tubes
56
What does GLC show because it works on solubility compared to stationary phase?
Different compounds will travel at different speeds | = different boiling points + temperature inside column
57
What is retention time?
The length of time a compound remains in a column
58
How do you calculate retention time?
Time taken from sample injected until max height for that compound
59
What does each peak in GLC correspond to?
Different compounds
60
What must you do after you calculate retention time?
Compare to known database
61
Which compound would come out last in GLC?
The most similar to stationary phase
62
Which compound would come out first in GLC?
The one that isn't similar but has the least no. of H bonds | = more H bonds = stronger attraction with stationary phase
63
How do you calculate the composition of a mixture in GLC?
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
How does mass spectroscopy work?
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
What does it mean if the ions are heavier?
Move more slowly = take longer to reach detector
66
What does M/Z of molecule equal + why?
Mr | As weight of e- is negligible
67
What does the M+ peak equal?
The total Mr for the compound
68
What is abundance?
The relative amount of ions in the spectra - usually given as a percentage
69
What is the equation for mass spectroscopy?
M (g) ----> M+ (g) + e-
70
Outline how a mass spectrometer would show the presence of Fe
M/Z value around 56
71
Why use the word "around"?
Abundance of isotopes
72
Outline how the mass spectrum would show how many different isotopes of sulphur were present
Count no. of M/Z peaks around 32
73
Relative atomic mass of sulphur found on Mars is different from relative atomic mass of S found on Earth. Why?
Different isotopic abundances
74
What can excess ionisation do when it is transferred to the molecular ion?
Can cause it to fragment
75
What happens when it fragments?
Produces smaller positive ion + radical Smaller positive ion detected Fragment ions can be broken down further
76
What is the M+1 peak caused by?
Carbon - 13 isotope
77
What is the Mr of CH3+?
15
78
What is the Mr of C2H5+?
29
79
What is the Mr of C3H7+?
43
80
What is the Mr of C4H9+?
57
81
What is the Mr of OH+?
17
82
What are the example of CH3CH2OH splitting?
CH3CH2OH (g) ----> CH3CH2OH+ (g) + e- CH3CH2OH+ (g) ----> CH2OH+ (g) + .CH3 CH3CH2OH+ (g) ----> CH3+ (g) + .CH2OH CH3CH2OH+ (g) ----> CH3CH2+ (g) + .OH
83
Whys is GLC not suitable technique for analysing mixture of dyes?
Because dyes not easily vaporised

A-Level Chemistry (26 decks)

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