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A-level Chemistry <3 > 6- Aromatic Compounds, Carbonyls, Nitrogen Compounds, Polymers, Analysis > Flashcards

6- Aromatic Compounds, Carbonyls, Nitrogen Compounds, Polymers, Analysis Flashcards

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1
Q

Formula of benzene

A

C6H6

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2
Q

What are the two ways of representing a benzene

A

kekulé model and delocalised model

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3
Q

What is the kekulé model

A

1865 germana chemist
Benzene made up of a planar ring of carbon atoms with alternating single and double bond between them
Each carbon atom is also bonded to one hydrogen atom

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4
Q

How was the kekulé model layer adapted to include

A

To say that the benzene molecule was constantly flipping between two forms ( isomers) by switching over double and single bonds

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5
Q

What proved kedulé structure can’t be completly correct

A

You would expect there to always be 3 bonds with the length c-c bond ( 154pm)
Theeee bonds with the length. C=C (134pm)

However x-ray diffraction studies have shown that all the carbon-carbon bonds on benzene have the same length ( 140pm) ( the bonds are equal length)

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6
Q

What is the delocalised model

A

Says that the p-orbitals of all 6 carbon atoms overlap to create pi system

The pi system is made up of two ring shaped clouds of electrons, one above and one below the plane of 6 carbon atoms

All bonds are the same length because all the bonds are the same

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7
Q

Do the electrons belong to a specific carbon atom in the delocalised model of benzene

A

No
They are delocalised

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8
Q

How is the delocalised model represented

A

As a circle inside the ring of carbons rather than as double or single bonds

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9
Q

What is the enthalpy changed called when a halogenation atom occurs

A

The enthalpy change of hydrogenation

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10
Q

The hydrogenation of benzene expremintalt is ……. Exothermic than expected, so …

A

Far less

So more energy must have been put into break bonds in Bernese than would be needed to break bonds in the kekulé structure

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11
Q

Is the benzene more or less stable that the kekulé structure would be

A

More

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12
Q

What else except less exothermic enthalpy change of hydrogenation shows that benzene is more stable than the kekulé model would suggest

A

Resistance to reaction

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13
Q

What is the stability of keklué through to be due to

A

Delocalised ring of electrons

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14
Q

What are compounds containing benezene rings called

A

Arenes or aromatic compounds

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15
Q

What is it called when the functional group for benzene is not the priority group

A

Phenyl

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16
Q

What should a benzene with an OH group attached be called

A

…..phenol

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17
Q

What conditions would be needed to have benzene undergo similar electrophilic addition reaction as alkenes

A

Hot benzene
UV

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18
Q

Why is benzene very stable

A

Delocalised ring of electrons above and below carbon atoms
They spread of the negative change

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19
Q

Why do benzenes not as strongly attract electrophilles as C=C double bond in alkenes

A

In alkenes the pi bond in the c=c bond is an area of localised high electron density, which strongly attracts electrophiles. In benzene, this attraction is reduced due to the negative charge being spread out.

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20
Q

Benzenes tend to react by electrophilic ……

A

Substitution

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21
Q

What is an electrophillic substitution reaction of benzene

A

Hydrogen atom being substituted by an electrophile
2 step mechanism, addition of electrophile to form a positively charged intermediate , followed by a loss of H+ form the carbon atom attached to the electrophile , this reforms the delocalised ring

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22
Q

What helps to make good electrophiles for benzene

A

Halogen carriers

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23
Q

What does an electrophile have to have to be able to attack a stable benzene ring

A

Strong positive charge

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24
Q

What do halogen carriers do

A

Accept a lone pair of electrons form a halogen atom on an elctophile,
As the lone pair of electrons are pulled away the polarisation in the molecule increases and sometimes a carbocations is formed. This makes the electrophiles stronger

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25
Q

Examples of halogen carriers

A

Aluminium halides
Iron halide
Iron

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26
Q

What do halogen carriers help

A

Halogens substitute into benzene ring

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27
Q

Explain a benzene will react with halogens
(Halogenation)

A
  • in the presence of an aluminium chloride catalyst, AlCl3
  • the catalyst polarieses the halogen, allowing one of the halogen atoms to act as an electrophile
  • during the reaction, a halogen atom is subsitiutued in play of a H atoms- called halogenation
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28
Q

Friedel-crafts reactions are really usefull in forming …

A

C-C bonds in organic synthesis

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29
Q

How are friedel-crafts reactions carriers out

A

Refluxing benzene’s with a halogen carrier and either a haloalkanes or an acyl chloride

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30
Q

How many types of friedel-crafts reactions are there

A

2

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31
Q

What are the two types of friedel-craft reactions

A

Friedel-crafts alkylation

Friedel-crafts acylation

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32
Q

What is Friedel-crafts alkylation

A

Puts any alkyl group onto a benzene ring using a haloalkanes and a halogen carrier

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33
Q

Friedel-crafts alkylation general reaction

A

C6H6 + R-X ——-> C6H5R + HX

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34
Q

What is friedel-crafts acylation

A

Substituted an acyl group for an H atom on benzene
You have to reflux benzene with acyl chloride instead of a choloalkame
This produced phenylketones

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35
Q

What does friedel-crafts acylation produce
And what is the exception

A

Phenylkerines
( unless R=Hm in which case an aldehyde called benzenecrabaldehyde or benzaldehyde is formedj

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36
Q

What is rhe general equations for a friedel-crafts acylation

A

C6H6 + RCOCl —-(reflux and AlCl3) —> C6H5COR + HCl

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37
Q

What do you needed to do to benzene to get nitrobenzene

A

Warm benzene with conc nitric acid and conc sulfuric acid

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38
Q

When you warm benzene with conc nitric acid and conc sulfuric acid you get nitrobenzene
What does rhe sulfuric acid do

A

Acts as a catalyst, it helps make nitroniym ion
NO2+, which is an electrophile
- It’s regenerated at the end of the reaction mechanism

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39
Q

What 2 equations show sulphuric acid acting as a catalyst in benzene to nitrobenzene

A

HNO3 + H2SO4 —-> H2NO3+ + HSO4-

H2NO3+ —-> NO2+. + H2O

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40
Q

What is mononitration

A

One NO2 group added

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41
Q

If you only wanted me NO2 group added to benzene to form nitrobenzene
What do you need to do

A

Keep the temperatures below 55°c

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42
Q

What 3 problems with kekulé model

A

Lack of reactivity of benzene
Thermodynamic stability of benzene
Bond lengths

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43
Q

How does lack of reactivity show a problem in the kekulé model

A

Based on kekulé model, benzene should decolorise bromine water
This doesn’t happen so far less reactive then kekulé model would suggest

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44
Q

How does thermodynamic stability of benzene show a problem in the kekulé model

A

Enthalpy of hydrogenation to cylcohenzae is is -119 kjmol-1
So you would expect hydprgenationof benzene to be -357kjmol-1
Yet it is -208 moldm-3
So more stable than expected with the kekulé model

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45
Q

What is conjugation (benzene)

A

Describe how electrons are delocalised across the whole molecule

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46
Q

What is the valence bond theory (benzene)

A

Explains bonding in benzenes as a series of unhybridised p-orbitals which overlap forming a cloud of e- density above and below the molecule
Which spreads e- stabilising the molecule

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47
Q

What type of reaction is a nitration of benzene

A

Electrophilic substitution

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48
Q

What are the conditions for a nitration of benzene

A

Conc sulphuric acid
50°c

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49
Q

What would happen if you increased temperature of nitration of benzene above 70

A

Claus further substitution

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50
Q

Equation to generate a nitronium Electrophilie ( in-situ)

A

HNO3 + H2SO4 —> NO2+ +HSO4 + H2O

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51
Q

What are some examples of halogen carriers

A

FeBr3
AlBr3

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52
Q

What would be the regeneration of a FeBr3 halogen carrier

A

H+ + FeBr4- —> FeBr3 + HBr

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53
Q

What is another name of methylbenzene

A

Toluene

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54
Q

What is a benzene with a Carboxylic group attached called

A

Benzoic acid

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55
Q

What is a benzene with NO2 attached called

A

Nitrobenzene

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56
Q

What benzene is not the highest priority what is it called

A

Phenyl group

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57
Q

What is a benzene with a NH2 attached called

A

Phenylamine

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58
Q

What is the common name for phenylamine

A

Aniline

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59
Q

What is benzene with a OH group attached. Called

A

Phenol

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60
Q

Is the relative density of benzene lower or higher than that of an alkene

A

Lower

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61
Q

What are the conditions of nitration of benzene

A

Conc H2SO4
500ºc
(HNO3)

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62
Q

What will happen in nitration of benzene if you increases the temperature above 70

A

Further subistutuon

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63
Q

What type of reaction is nitration of benzene

A

Electrophilic subsitutuon

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64
Q

Formation of br+ Electrophile with a halogen carrier

A

Br2 + FeBr3 —> br+ +FeBr4-

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65
Q

Solubility of phenols

A

OH group forms h bonds with h20 so mildly soluble
But the benzene ring is non polar so not that soluble

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66
Q

Know how a phenol acts as an acid

A

(About releasing H+ )
Learn the diagram

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67
Q

When phenol reacts with a strong base, what kind of ion forms

A

Phenolate

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68
Q

What is the name of position 2/6 on benzene

A

Ortho

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69
Q

What is the name of position 3/5bon benzene

A

Meta

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70
Q

What is the name of position 3on benzene

A

Para

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71
Q

What position/s does an electron donation group activate

A

Ortho
Para

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72
Q

What are some examples of electron donation groups

A

OH
Alkyl groups
NH2 or NHR
F, Cl, Br, I

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73
Q

What position/s does electron withdrawing group activate

A

Meta
(By deactivating Ortho / para )

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74
Q

What are some example of electron withdrawing group s

A

NO2
COOH
COOR
SO3H
CHO
CN
NR3+

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75
Q

What kind of conditions will phenol react with bromine

A

Mild

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76
Q

Why is phenol more reactive to Electrophilies than benzene

A

Lone pairs on OH can contribute e- density into ring

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77
Q

Why are phenol more likely to undergo Electrophilic substitution than benzene

A

One of the lone pairs of electrons in a p-orbital of the oxygen atom overlaps with the delocalised ring of electrons in the benzene ring
So the lone pair of electrons form the oxygen atom is partially delocalised int the pi system
Increases the electron density of the ring
Making it more likely to be attacked by electrophiles

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78
Q

In an unsubstitutec benzene, all carbon atoms are the same so electrohpiles react with .,,,

A

Any

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79
Q

What do electron donating groups do the electron density

A

They have electrons in orbitals that overlap with the delocalised ring and increase its electron density
In particular they increase density at carbons 2, 4, 6

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80
Q

What does electron withdraw ring group do to electron density (how)

A

Doesn’t have any orbitals that can overlap with the delocalised ring
And it’s electronegative
So it withdraws electron density form the ring
It withdraws electron density at 2,4,6

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81
Q

Does phenol decolourise bromine water

A

Yes as it’s more reactive than benzene

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82
Q

What happens when penal is shaked with bromine water

A

OH is electron donating
So directs substituting carbons, 2 4 6
Insoluble in water and precipitates out
Smells of antiseptic

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83
Q

Phenol reacts with dilute nitric acid to give …

A

Two isomers of nitrophenol and water

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84
Q

Is it easier to nitrate phenol or benzene
And why

A

Phenol
Activating effect of OH group

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85
Q

How does phenol react with sodium hydroxide

A

At room temp in a neutralisation reaction
To form sodium phemoxide and water

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86
Q

Does phenol react with sodium carbonate
Why?

A

No
Phenol is not a strong enough acid

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87
Q

T or f
Aldehyde and ketones are carbonyl compounds

A

T

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88
Q

How are aldehydes and Carboxylic acids made

A

Oxidising primary alcohols
You can use acidified dichromate (vl) ions to mily oxidise alcohols

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89
Q

What is the orange to green colour change due to (oxidising alcohols )

A

Orange dichromate (vl) ion is reduced to the green chromium (lll) ion

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90
Q

You can ….. aldehydes and ketones back to alcohols

A

Reduce

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91
Q

What is used to show a reducing agent

A

[H]

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92
Q

What is the vernal equation for reducing an aldehyde to a primary alcohol

A

RCOH + 2[H] ——-> RCH2OH

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93
Q

What is the general equation to reduce a ketone to a secondary alcohol

A

H
l
RCOR +2[H] ———> R-C-OH
l
R’

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94
Q

What is the reducing agent normally for reducing aldehydes and ketones back to Alcon
S

A

NaBH4
(sodium tetrehyseiborate(lll)
Or
Sodium borohydride)

Normally dissolves in water with methanol

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95
Q

What happens in a nucleophilljc addition reaction.

A

A nucleophile attacks the molecule and an extra group is added to it

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96
Q

Describe how aldehyde and ketones are reduced back to alcohols
(The mechanism(

A

The reducing agent , supplied hydrogen ions
H- has a lone pair of electrons so it’s a nucleophile and can attack rhe delta+ carbon on the carbonyl group of an aldehyde or ketone
Then adds water

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97
Q

Hydrogen cyanide will react with carbonyls a what typeof reaction

A

Nucleophilic addition.

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98
Q

Hydrogen cyanide will react with carbonyls to produce

A

Hydroxynitriles

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99
Q

Is hydrogen cycandid a strong or weak acid or alkali

A

Weak acid

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100
Q

How does hydrogen cyanide dissociates in water

A

Partially to form H+ and CN- ions

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101
Q

Is CN- a nucleophile or an electrophile

A

Nucleophile

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102
Q

Hydrogen cyanide will react with carbonyls, describe the mechanism

A

The CN- ion attacks the slightly postivibe carbon atom and donates a pair of electrons to it. Both electrons from the double bond transfer to the oxygen

The H+ (from hydrogen cyanide or water ) bonds to the oxygen to form the hydroxyl group

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103
Q

Hydrogen cyanide will react with carbonyls to produce a hydroxynitrile.
What are the dangers and what should be done to mitigate this risk

A

Hydrogen cyanide is a highly toxic gas
When thus reaction is done in the laboratory a solution of acidified sodium cyanide is used instead to reduce the risk
The reaction should be done in a fume cupboard

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104
Q

What can be used to test for aldehydes and ketones

A

2,4-dinitrophenylhydrazine

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105
Q

What is 2,4-dinitrophenylhydrazine (2,4-DNP) also known as

A

Brady’s reagent

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106
Q

Describe the 2,4-dinitrophenylhydrazine test form aldehydes and ketones

A

When it’s dissolved in methanol and conc sulfuric acid it will react with carbonyl groups to form a bright orange precipitate
This only happened with c=o groups, (not COOH) so only tests for aldehydes and ketones

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107
Q

How is the orange precipitate form the 2,4-dinitrophenylhydrazine test for aldehydes and ketones, used to know exactly which carbonyl compound it produced.

A

It’s a derivative of the carbonyl compound. Each carbonyl compound produces a crystalline derivative with a differnt melting point
So measure the melting pound of the crystals and compare it against the known melting points of the derivatives, you can identify the carbonyl compounds

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108
Q

What test lets you distinguish between a aldehyde and a ketone, and what basic fact does it use

A

Tollens reagent
That an aldehyde can be easily oxidised to a Carboxylic acid but a ketone can’t

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109
Q

What is tollens reagent

A

Colourless solution of silver nitrate dissolved in aqueous ammonia

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110
Q

How is tollens reagent used to test for an aldehyde

A

When heated togetehr in a test tube ,the aldehyde is oxidised and the silver ions in the tollens reagent are reduced to silver causing a silver mirror to form
The test tube should be heated in a breaker of hot water, rather than directly over a flame

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111
Q

What can tollens reagent also be called

A

Ammoniacal silver nitrate

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112
Q

What equation shows tollens reagent reaction

A

Ag(NH3)2. ^+ (aq) +e- —> Ag(s). + 2NH3(aq)

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113
Q

In synthesis of organic solids the desired products will oftern by ……

A

Trapped in a solvent / reaction mixture

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114
Q

How do you carry out reduced pressure filtration

A
  1. Place filter paper into the Bucner funnel and wet with a few drops of the solvent used in the reduction
    2.turn on the vacuum pump to apply suction to the filter paper - can check suction be putting hand over Büchner funnel
    3.slowly pour the reaction mixture into the filter paper
  2. Rinse the crystals with more solvent and leave under suction for a few minutes for drying
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115
Q

Describe purification by recrystallisation

A
  1. War, a fixed volume of solvent using a water bath
  2. Tip impure sample into a second conical flask
  3. Slowly add the hot solvent to the impure sample until it dissolves ( add minimum amount of solvent needed)
  4. Once the impure produce has dissolved, allow the suction to cool. Pure crystals should start toform in the conical flask
  5. When crystals stop forming, obtain the dry crystal by reduced pressure filtration
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116
Q

What is reagent used to test for carbonyls

A

2,4 - DNP
Or
(Brady’s reagent)
Or
DNPH

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117
Q

Explain the steps of the test for a carbonyl

A

1) add excess 2,4 - DNP to a clean test tube
2j add unknown solution
3) if no crystals form add a few drops of sulfuric acid
4) if carbonyl is present an orange precipitate will form

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118
Q

What reagent is used to distinguish between an aldehyde or a ketone

A

Tollens regent

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119
Q

What is tollens reagent

A

Silver nitrate in a solution of ammonia

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120
Q

What isnthe ionic Eq for rhe silver mirror test
And what type of reaction is it

A

Ag+ ( aq) + e- —> Ag(s)
Reduction

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121
Q

What is a positive test for the tollens reagent

A

Silver mirror forms

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122
Q

Describe the C=C bond based on what kind of reactions it undergoes

A

High electron density so easily attracts (susceptible) to electrophiles

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123
Q

Describe the C=O bond based on what kind of reactions it undergoes

A

Permientdipole (polar bond)
Slightly positive carbon will react with strong nucleophile

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124
Q

What type of reaction is a carbonyl to an alcohol

A

Nuclophilic additon
Or
Reduction

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125
Q

What is a reducing agent represented by

A

[H]

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126
Q

How many moles of reducing ages is used to reduce an aldehyde or ketone

A

2

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127
Q

What is used to reduce and aldehyde or ketones and into what

A

Sodium borohydride (naBH4) and H2O
Alcohol

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128
Q

What is was way of extending the carbon chain

A

Addison of cyanide to am aldehyde or ketone

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129
Q

Describe the test to distinguish between an aldehyde and a ketone

A

1) a few drops of silver nitrate into a test tube
2) add dilute ammonia - tollens reagent forms
3) add approx, same amount of unknown solution
4) leave test tube in a water bath at 50°c
5) if silver mirror forms an aldehyde is present

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130
Q

What is the name of COOR

A

A Carboxyl functional group

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131
Q

What is another name for 2-hydroxybenzoicacid

A

Salicyclic acid

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132
Q

What are Carboxylic acids used In

A

Medicines
Food
Citrus fruits
Drinks

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133
Q

Describe the solubility of a Carboxylic acid

A

The oh group can from hydrogen bonds with water ( and the c=o group )

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134
Q

When do Carboxylic acids stop being soluble

A

When the carbon chain exceeds 4

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135
Q

Are carboxylic acids considered strong or weak acids

A

Weak acids so they partially dissociate into its ions

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136
Q

What is the PKA of a carboxylic acids

A

5

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137
Q

Suffix for a Carboxylic acid

A

Oic acid

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138
Q

What do carboxylic acids partially dissociate into
And where does the equilibrium lie

A

Carboxylate ions and H+ ions
To the left because most of the molecule doesn’t dissociates

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139
Q

Do hydrogen bonds exist between carboxylic acids
Why?

A

Yes
They are polar since electrons are drawn towards the o atom. H bonds are able to from between the highly polarised H(slightly positive) and O(slightly negative) atoms on other moelcuels

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140
Q

What is the suffix for salts of Carboxylic acids

A

Oate

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141
Q

How do carboxylic acids react with more reactive metals

A

In a redox reaction to form a salt and hydrogen

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142
Q

What salt would form with ethanoic acid and magnesium,I

A

Magnesium Ethanoate

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143
Q

What do carboxylic acids react with carbonates to from

A

Salt
Co2
Water

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144
Q

Carboxylic acids are neutralised with other …… to got, ….. and ……

A

Bases
Salt
Water

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145
Q

What bases can neutralise carboxylic acids

A

Alkalis
Metal oxides

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146
Q

How are acyl chlorides formed

A

Form reacting carboxylic acids with socl2

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147
Q

What functions group do acyl chlorides have

A

COCl

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148
Q

What is the general formula for an acyl chloride

A

CnH2n-1OCl

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149
Q

What is the suffix for acyl chlorides

A

Oyl chloride

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150
Q

What is the name for SOCl2

A

Thionyl chloride

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151
Q

What is replaced and by what when carboxylic acids react with socl2

A

The OH group in the acid is replaces by -Cl.

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152
Q

What is formed when propanoic acid reacts with socl2

A

Propanoyl chloride
SO2
Hcl

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153
Q

What happens when an acyl chloride reacts with coldwater o

A

Vigorous reaction producing Carboxylic acid and Hcl

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154
Q

What happens when an acyl chloride reacts with alcohols and in what conditions

A

At room temp
Ester and hcl

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155
Q

Acyl chlorides and alcohols
And
Carboxylic acids and alcohols
Both produce esters, what is the differnce

A

Acyl choride are irreversible, they are much easier and faster

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156
Q

What happens when an acyl chloride reacts with ammonia and in what conditions

A

A violent reaction at room temp producing a primary amide and hcl

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157
Q

What happens when acyl chlorides react with amines and in what conditions

A

Tom temp
A violent reaction producing a secondary amide

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158
Q

Each time Cl ( in acyl chlordies) is Substituted by an oxygen or nitrogen group What gas is given of
And what type of reaction is this

A

Hydrogen chloride
Nucleophilic addition-elimination reaction

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159
Q

Why would u react a phenol with an acyl choride to make an ester over with a Carboxylic acids

A

It’s faster

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160
Q

Phenol + acyl chloride :

A

Ester

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161
Q

Describe the reaction of ethanoic choride and phenol

A

Slowly at room tmep
To produce the ester : phenyl ethanoate and hydrogen choride

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162
Q

How to distinguisha Carboxylic acid

A

It’s the only organic compound acidic enough to react with carbonates
(Phenols can’t react with carbonates)

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163
Q

What is a Carboxylic acid derivative

A

Something that can be made form a Carboxylic acid

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164
Q

What is an ester mademfrom

A

Reacting an alcohol with a Carboxylic acid or a Carboxylic acid derivative

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165
Q

How to name an ester

A

The first bit comes form the alcohol
The second but comes from the Carboxylic acid ( swap the oic acid for oate)

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166
Q

What conditions are needed to make an ester from a Carboxylic acid and an alcohol

A

Acid catalysts and heat

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167
Q

What acidic catalysts is usually used when making an ester

A

Conc sulfuric acid

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168
Q

What is the reaction called when a Carboxylic acid and an alcohol react

A

Esterification

169
Q

Is esterification reversible? So what does this mean for collecting products

A

Yes
You need to separate out the product as it’s formed

170
Q

How can you separate a small ester from its products as it’s formed

A

Warm the mixture and just distil off the ester, because it’s more volatile than the other compounds

171
Q

How can you separate a large ester from its products as it’s formed

A

Larger esters are harder to form so it’s best to heat them under reflux and use fractional distillation to separate the ester from the other compounds

172
Q

What type of reaction is esterification as well

A

Condensation

173
Q

What else is produced in esterification as well as the ester

A

Water

174
Q

What is an acid anhydride made from

A

2 carboxylic acids

175
Q

Acid anhydrides can be reacted with alcohols to make….

A

Esters

176
Q

How is an ester made form an acid anhydride

A

Warmed with the alcohol
(No catalyst needed)

177
Q

what are the products of acid anhydrides and alcohols

A

Ester and a Carboxylic acid

178
Q

How can you separate the ester and Carboxylic acid (after forming when reacting acid anhydrides with alcohol)

A

Fractional distillation

179
Q

When an acid anhydride is formed what else if made

A

A water

180
Q

Look at how acid anhydrides and alcohols react

A
181
Q

When an alcohol reacts with acyl chlorides what is formed

A

An ester and hydrogen chloride gas (toxic)

182
Q

Esters are hydrolysed to from…..

A

Alcohols

183
Q

What are the 2 ways to hydrolyse esters

A

Using acid hydrolysis
Or base hydrolysis

184
Q

What is a similarity between acid hydrolysis and base hydrolysis of esters

A

Both types you get an alcohol

185
Q

Explain acid hydrolysis of an ester

A

Splits an ester into a Carboxylic acid and an alcohol
You have to reflux the ester with a dilute acid, such as hydrochloric or sulfuric

186
Q

Is acid hydrolysis of an ester reverisble

A

Yes

187
Q

Acid hydrolysis of an ester is revserble
What is needed to push the equilibrium over to the right

A

Lots of water

188
Q

Explain base hydrolysis of an ester

A

Reflux rhe ester with a dilute alkali, such as sodium hydroxide

189
Q

What is made from base hydrolysis of an ester

A

Carboxylate slat
Alcohol

190
Q

Is base hydrolysis of an ester reverisble

A

No

191
Q

What else can be reacted with carboxylic acids to make acyl chlorides except for, socl2
To make what products

A

Pcl5
Acyl chloride , pocl3, hcl

192
Q

What is acyl choroide susceptible to and why

A

Highly electropositive centre due to electronegative o and Cl
Susceptible to attack from nucleophile

193
Q

In reaction of acyl Chlorides and alcohols, why would you need dry conditions

A

H2O would be a competing nucleophile and Carboxylic acid would also be made and lower the yield, they would then need separating

194
Q

What is another name of alkali hydrolysis

A

saponification

195
Q

What does saponification make

A

Carboxylate salt and alcohol

196
Q

Which conditions favours the hydrolysis of esters

A

Alkaline
Forms a salt wich is very favourable so thus reaction goes to completion whereas acid hydrolysis doesn’t go to completion

197
Q

Once acyl choice and ammonia have complained to make the amide and hcl
What then reacts
So what is included in the overall equation

A

Hcl and excess ammonia
Hcl + nh3 -> nh4+cl-

So you put 2 moles of ammonia and the product is not hcl it is NH4Cl

198
Q

Once the acyl has reacted with primary amines and hcl is formed
What happens next

A

Hcl reacts with the primary amide forming
RNH3Cl

199
Q

If one or more of the hydrogens in ammonia (NH3) is replaced with an organic group, what do you get

A

Amine

200
Q

If nitrogen is bonded to 2 alkyl groups what is it called

A

Secondary amine

201
Q

What do you get if nitrogen is bonded to four alkyl groups

A

A positively charged quaternary ammonium ion

202
Q

Why are amines bases

A

There’s a lone pair of electrons on the nitrogen of the amine that’s able to accept protons.

203
Q

Amines are neutralised by acids to make ….

A

Ammonium salts

204
Q

What salt does ethylamine make when reacted with hcl

A

Ethylammonium chloride

205
Q

How can aliphatic amines be make

A

Heating a haloalkanes with excess ethanolic ammonia (ammonia dissolved in ethanol)

206
Q

Amines can be made from haloalkanes
what is made exactly, why

A

Mixture of primary, secondary and tertiary amines, and quaternary ammonium salts
As more than one hydrogen is likely to be substituted

207
Q

How can you separate a mixture of amines

A

Fractional distillation

208
Q

What will happen if bromoethane with react with ammonia

A

Forms ethylamine
This then can also react with bromoethane to form, diethylamine

209
Q

How are aromatic amines made

A

Reducing a nitro compound

210
Q

How are nitrocompounds reduced
And what does this make

A

Heat mixture of nitro compound, tin metal and conc. hcl
Under reflux
A salt

211
Q

To get an aromatic amine from reducing a nitro benzene
What else is added

A

Sodium hydroxide

212
Q

Reduction of nitro compound to an amine
What else is released

A

Water

213
Q

T or f
Amides are Carboxylic acid derivative s

A

T

214
Q

What are amides functional group

A

CONH2

215
Q

Why do amides behave differently from amines

A

The carbonyl group pulls electrons away from the rest of the CONH2 group

216
Q

What types of amides do you get

A

Primary and secondary

217
Q

What does if an amide is primary or secondary depend on

A

How on atoms the nitrogen is bonded to

218
Q

What group does an amino acid have

A

A basic amino group ( NH2) and an acidic Carboxyl group (COOH)

219
Q

What is an a- amino acid

A

Both groups are attached to the same carbon atom - the a-carbon

220
Q

What is the general formula for an a-amino acid

A

RCH(NH2)COOH

221
Q

How do amino acids react with alkali

A

Carboxylic acid group in amino acid can react with an alkali to form a conjugate base - RCH(NH2)COO-
This can combine with a potivive ion to from a salt

222
Q

How can amino acids react with an acid

A

Amino group meanwhile can react with an acid to from a salt of the conjugate acid

223
Q

NH2 group on amino acid + HCL what salt group is fomred

A

Cl- H3N+

224
Q

What do amino acids react with alcohols to form
What are the conditions

A

ester
Strong acid catalysts ( sulfuric )

225
Q

What is a chiral carbon

A

A carbon atom which has 4 differnt group attached to it

226
Q

Chiral carbons can be arranged in 2 ways so that 2 differnt molecules are made
What are these called

A

Enantiomers or optical isomers

227
Q

What is an enantiomer

A

Non superimposable mirror image

228
Q

If a molecule can be superimposed on its mirror image it ….

A

it’s achiral and so it doesn’t have an optical isomer

229
Q

What does it mean that optical isomers are optically active

A

They rotate plane- polarised light

230
Q

What is the difference between normal light and plane polarised light

A

Normal light vibrates in all directions , but plane polarised light only vibrates in one direction

231
Q

What are enatiomers sometimes identified as

A

D or L

232
Q

One enantiomer rotates the plane-polarised light …….. and the other….

A

Clockwise and the other rotates the same amount in the anti-clockwise direction

233
Q

Are chiral compounds common in nature
Example

A

Yes
But you usually only find one enantiomers
Eg, all naturally occurring AA are L, most sugars are D

234
Q

How do you draw 2 optical isomers

A

Identify the chiral carbon ( with 4 differnt substituents attached)
Draw one enantiomer in a tetrahedral shape , then draw a mirror image beside it

235
Q

Do molecules have more than one chiral centre

A

They can

236
Q

If a carbon is attached the same ring twice is it chiral

A

It can be if the order of atoms in the rings it differnt depending on which way you go rounf

237
Q

If a molecule has more than one chiral centre
How many optical isomers will it have

A

More than 2

238
Q

If a molecule has 2 chiral centres how many optical isomers are their

A

4

239
Q

How to name a primary amine

A

Suffix - amine
Stem - chain

240
Q

How to name secondary amines

A

N-
The shorted chain first
Then the longest. Chain with suffix

241
Q

How to name tertiary amine

A

N,N-
Then the same rules as amine

242
Q

What do amines make good….

A

Nucleophile as they can donate a pair of electrons

243
Q

The bigger the amine the …. It is as a nucleophile

A

Worse

244
Q

What can you describe an amine as

A

Lewis base - donates lone pairs
Brønsted lowery base - accepts protons

245
Q

….. substituted amines are more basic

A

More

246
Q

Why are more substituted amines more basic

A

Inductive effect
The EDG will enrich electron density so better at accepting protons

247
Q

What happens to basic properties if NH2 is attached to benzene

A

Ewg
Lone pair delocalised into the ring nitrogen is less e- rich - less able to accept protons

248
Q

Explain the boiling point in amines

A

hydrogen bonding So relatively high
Requires more energy to overcome

249
Q

Describe the solubility in amines

A

Lower mass amines can form H bonds with water - effect lessens with larger amines
Soluble in organic solvents ( non/ less polar solvents)

250
Q

Which functional groups will have distinctive smells

A

Ester

251
Q

Desicbe addiction reactions

A

Two molcules join together to from a single product . Involves breaking a double bond

252
Q

Desicbe elimination / dehydration reactions

A

Involves removing a functions group which is released as part of a small molecule
Often a double bond is bored

253
Q

Desicbe a substitution reaction

A

A function group on a molecule is swapped for a new one

254
Q

Desicbe a condensatiom reaction

A

Two molecules get joined together with the loss of a small molecule
Eg, water or hcl

255
Q

Hydrolysis reaction description

A

Water is used to split apart a molecule, creating two smaller ones. Opposite of condensation

256
Q

Desicribe oxidation reaction

A

Loss of election
Usually in organic means gaining an oxygen or loosing a hydrogen

257
Q

Reduction reaction description

A

Reduction is gain or elections
In organic chem it usually means gaining a hydrogen atom or loosing an oxygen atom

258
Q

Why do chemcial need a synthetic rote to get form one compound to another

A

Vital for designing medicines
Good more making imitations of useful natural substances when the real things are hard to extract

259
Q

If your asked how to make one compound from another what do you need to include

A

Any special procedures ( eg, reflux)
The conditions needed
Saftey precautions eg, fume cupboards

260
Q

Why do you reflux

A

Organic reactions are slow and substances usually flammable and volatile ( low bp )
If you stick them in a beaker and heat the, with a bunsen burner they will evaporate or catch fire before they have time to react

261
Q

How does reflux work

A

Heated in a flask fixed to a Liebig condencer - so when mixture boils , the Vapor’s are condemned and recycled back into the fAsk . This stops reagent being lost form the fAsk and have time to react

262
Q

How can organic solids be purified

A

Recrystallisation
dissolve solid in solvent to make a saturated solutions, then cool. Crystals form becasue wehn it cools the solubility falls - when it reaches the point it can’t stay in the solution the crystals form

1j very hot solvent added to impure solid until it just dissolves
2 ) this gives a saturated solution of the impure product
3j cool down slowly
4) crystals of the rod ict form as it cools . Impurities stay in solution ( as they are m much smaller amounts so take longer to crystallise out)
5) crystals removed by reduced pressure filtration and washed with ice cold solvent. Dried

263
Q

When does recrystallisation only work ( solvent)

A

If the solid is very soluble in the hot solvent but nearly insoluble when the solvent is cold

If the product isn’t soluble enough in the hot solvent you won’t be able to dissoble it at all
If the product is too soluble in the cold solvent most of it will stay in the solution after cooling. When u filter it you will loose most of your product giving a low yield

264
Q

Explain reduced. Pressure filtration

A

If your product is solid you can separate it from any liquid impurities by filtering under reduced pressure

Reaction mixture poured into the Büchner funnel with a piece of filter paper. The Buchner gunner is on top of a sealed sidearm flask which is conncectef to a vacuum line . Causing it to be plunder reduced pressure

Causes suction in the funnel so liquid can quickly pass into the flask and leave behind dry crystals

265
Q

If they’re impure the melting point is…… and the boiling point is …..

A

Lowered
Raised

266
Q

What is different about boiling points and melting points if very impure

A

Occur across a wide range of temps

267
Q

How can you accurately measure melting point s

A

Put a small amount of the solid in a capillary tube and place it in a beaker of oil with a very sensitive thermometer.
Slowly heat, with constant stirring, until the solid just melts and read the temp

268
Q

What can you do with a measure melting pint

A

Compare it to known data book values to determine its purity

269
Q

What are the 2 types of polymerisation

A

Additon
Condensation

270
Q

What type do polymerisation do alkenes join up

A

Additon

271
Q

When is condensation polymers formed

A

Two types of monomers each of which has at least 2 fg

The fg group on one monomer reacts with a group on the other type of monomer to form a link

272
Q

In condensation each time a link Is formed what happens

A

A small molecule is most ( oftern water)

273
Q

What do condensation polymers include

A

Polyesters
Polyamides

274
Q

What is the link between monomers in polyesters

A

Ester link

275
Q

What is the bond formed between monomers in polyamides

A

Amide ( CONH)

276
Q

How can condensation polymerisation be reversed

A

Hydrolysis

277
Q

In practice, what is wrong with hydrolysis with water and what is done instead

A

Too slow
So down with acid or base

278
Q

In polyamides will hydrolyse more easily y with acids or bases

A

Acids

279
Q

What do polyamides hydrolyse into
(After being reacted with what in the Eq)

A

n dicarnoxylic acid
n diamine

2nH2O

280
Q

Have a look at hydrolysis reaction on page 190

A
281
Q

Will polyesters hydrolyse more easily with an acid or a base

A

Base

282
Q

What is formed form hydrolysis of a polyester

A

Metal salt for the Carboxylic acid (dicarboxylic acid salt)
Diol

283
Q

Carboxyl group reacts with amino group reacts to form

A

Amide group

284
Q

What is an amide group

A

CONH

285
Q

What is lost each time an amide link is formed

A

Water

286
Q

What is reacted to make a polymaide

A

Dicarboxylic acid
Diamine

287
Q

What reacts to make polyesters

A

Reactions between dicarboxylic acids and diols

288
Q

Compounds were one Carboxylic acid group changed to an acyl chloride
How will it react differnt in condensation polymerisation

A

It will still from a polyester or a polyamide
Instead of water, hcl is eliminated

289
Q

How do you draw the monomer form a polymer chain ( additon

A

Find the repeate unit
For an addition polymer the backbone of the repeat unit will always be 2 carbons long

You need to remove empty bonds that join onto the next relay until and replace central carbon carbon bond with a double bond

290
Q

How do you find the monomers form condensation polymers

A

1) find the amide link or ester link then break down the middle
2) as h or oh on to both ends to find the monomer
( add h to O or N, or OH to C)

291
Q

If the monomer units are dicarboxylic acids or diamine
Where does H2O come form

A

OH form dicarboxylic acid
H from amine

292
Q

If the monomer units are dicarboxylic acids and a diol
Where does H2O come from

A

H from diol
And OH form CA to form an ester

293
Q

If a molecule contains both amino and an alcohol and react with dicarboxylic acids in a condensation polymerisation reaction
What happens

A

Polymers contain amide and ester links

294
Q

If a molecule has a CA and either an alcohol and amine group
What can happen

A

It can polymerise with itself to form a condensation polymer with only one monomer

295
Q

Why is ammonia a good nucleophile

A

Can donate of e

296
Q

What would the products look like for chlorobutane + ammonia =

A

Butylammonium chloride

297
Q

Structural formula for butyl ammonium chloride

A

Ch3CH2CH2CH2N+H3Cl-

298
Q

What do you do with butyl ammonium chloride to get your butyl amine

A

Work up with naOH

299
Q

Ch3CH2CH2CH2N+H3Cl- add NaOH
What does it produce

A

CH3CH2CH2CH2NH2
NaCl
H2O

300
Q

What can happen after butyl amine is produced

A

It’s still a nucleophile so at risk of undergoing further subsitituion

301
Q

What lowers the risk of further substitution if you only want to make a primary amine

A

Excess NH3
As NH3 is a better nucleophile than the primary amine you have produced

302
Q

Understand Eq when fu5her substitution happens on the amine made

A
303
Q

What are aromatic amines made from

A

Nitro benzene + 6[H]

304
Q

What are the conditions for synthesising aromatic amines from nitrobenzene

A
  1. Sn , conc hcl under reflux
  2. Excess naOH
305
Q

Nitrobenzene + 6[H] produced what

A

phenylamine + 2H20

306
Q

What is made form nitrobenzene + Sn and conc hcl under reflux

A

Phenyl ammonium chloride salt

307
Q

How does cyanide form a new carbon carbon bond

A

CN-
Ion containing a negatively charged carbon atom, so it’s a nucleophile.
It’ll react with carbon centres that have a slight positive charge to crest a new carbon carbon bond.

308
Q

What is the compound that is initially produced when a cyanide ion attacks a slight potivive carbon centre

A

Nitrile

309
Q

What form of cyanide can you react with the slight positive carbon centre

A

KCN
NaCN
HCN

310
Q

if C=O reacts with CN
what does rhe C=O bond go to

A

C-OH

311
Q

Describe how cyanide ions react with haloalkanes

A

Nucleophilic substitution
Reflux haloalkanes with NaCN or KCN in ethanol. A nitrile is formed

312
Q

Finish the Equation
R-X + CN- —->

A

R-C=- N + x-

313
Q

Why is adding CN on useful

A

Once you have extended the carbon chain
It’s easy to convert nitrile to a new function groupo as nitrile group is very reactive

314
Q

What can nitriles be used to form

A

Primary Amines

315
Q

How can you reduce nitriles to primary amines

A

1) use lithium aluminium hydride (LiALH4- a strong reducing agent ) , followed by some dilute acid
2)also you can reduce the nitrile ( or hydroxynitiel) with sodium metal and ethanol

316
Q

Can you reduce hydroxynitirles with LiAlH4

A

Yes

317
Q

RCH2CN + ……
To form a primary amine
Finish the Eq

A

4[H] —> RCH2CH2NH2

318
Q

LiAlH4 and sodium metal/ ethanol
What are the positives and negatives

A

Too expensive for industrial use but great for the lab.

319
Q

What is used instead of LiAlH4 and sodium in the industry

A

Nitriles are reduced using hydrogen gas with a metal catalyst such as platinum or nickel at a high temp and pressure - called catalytic hydrogenation

320
Q

What is reducing using hydrogen gas and metal catalyst called

A

Catalytic hydrogenation

321
Q

RCH2CN + 2H2
What is made

A

RCH2CH2NH2

322
Q

What are nitriles be hydrolysed to form

A

CA

323
Q

How can nitriles be hydrolysed into CA

A

Reflux in dilute HCl
Then the nitrile group will be hydrolysed to form CA

324
Q

RCH2CN +
Complete the equation to form a CA

A

2H2O + HCl —> RCH2COOH + NH4Cl

325
Q

How can you tell if a synthetic route it likely to include formation of nitrile or hydroxynitrile

A

If the product of a synthetic route contains more carbon in the chain than the starting compound

326
Q

Aside from CN what is another way of extending the carbon chain

A

Friended crafts reactions

327
Q

What do you use to test for double bonds

A

Bromine water
Orange to colourless

328
Q

How do you test for haloalkanes

A

Silver nitrate aq ( + ethanol)
White, cream ,yellow p

329
Q

How do you test for phenols

A

You are testing the weak acid nature of
1) NAOH, strong base so will react with any acid
Acid - solid will dissolve, a colourless solution of a sodium salt will form

2) carbonate. Much weaker base , only react with strong acids not weak acids ( like phenols )
Strong acid - effervecnesce
Phenols- nothing

330
Q

How do you test for CA

A

React with carbonates to form a salt , CO2 and water
Fizz and turn liemwater cloudy

331
Q

How do you test for primary and secondary alcohols

A

Acidified potassium dichromate
Primary - organs - green
Secondary - orange - green
Tertiary - nothing

332
Q

What is chromatography used for

A

To separate stuff in a mixture
Once the mixture is separated out you can oftern identify the differnt components

333
Q

What are the 2 types of chromatography you need to know about

A

TLC ( thin layer chromatography)
GC ( has chromatography)

334
Q

What is tlc

A

A solvent such as ethanol moved over a glass of plastic plate
Which is covered in thin layer of solid ( silica gel or aluminium powder)

335
Q

Method to set up TLC

A

1) draw a pencil line near the bottom of the plate and put a spot of the mixture to be separated on the line
2) dip the bottom of the plate ( not the spot) into a solvent
3) as the solvent spreads up the plate , the differnt substances in the mixture move with it , but differnt distances so they separate put
4) when the solvent nearly reached the top of the plate , take the plate out and mark the distance that the solvent has moved ( solvent front) in pencil

336
Q

How can you identify each spot on a TLC plate

A

Rf value
Then look up in table of known values

337
Q

How to calculate Rf

A

Distance travelled by spot
—————————————-
Distance travelled by solvent

338
Q

How far an organic molecule travels up the plate in TLC depends on what

A

How strongly its attracted to the layer of solid on the surface of the plate

339
Q

What is the attractions between substance and the surface of the plate is called?

A

Adsorption

340
Q

A substance that is strongly adsorbed
How will it move in TLC

A

Move slower
So wont travel as far as one that’s only weakly adsorbed
So they have differnt Rf values

341
Q

What effects how strongly adsorbed a particular substance is to the plate in TLC

A

-Chemical properties such as polarity

  • solid coating on the plate
  • the solvent used
  • extral values such as temperature
342
Q

Small changes can effect Rf values
So what should be done to check TLc results

A

Once you have identified what you think an unknown compound is, it’s best to check your right by running a pure sample of the known substance alongside your unknown compound on a TLC plate
Identical substances should travel the same distance up the plate ( have the same rf vales )

343
Q

Describe gas chromatography

A

The sample to be analysed is injected into a stream of gas
Which carries iron through a coiled tube coated with a Viscous liquid ( such as an oil) or a solid

The components of the mixture constantly dissolve in the oil or onto the solid , evaporate back into the gas and then redissolve as they travel through the tube

Time taken for the substance to pass through the coiled tube and reach the detector is called retention time and can be used to identify the substance

344
Q

What is retention time (GC)

A

Time taken for the susbtance to pass through the soiled tube and reach the detector

345
Q

Page 206
Ensure You can level a GC and TLC

A
346
Q

What does a gas chromatogram show

A

A series of peaks at the times when the detector senses something other than the Carrier gas leaving the tube

347
Q

What can gas chromatograms show

A

The identity of substances within the sample and their relative proportions

348
Q

What does each peak on a chromatogram correspond to

A

A substance with a particular retention time

349
Q

What are retention times measure form for each peak on a gas chromatogram

A

Zero to the centre of each peak

350
Q

What can u use retention times in GC for

A

Can be looked up in a reference table to indentify the substances present

351
Q

What does the area under each peak in a gas chromatogram represent

A

It’s proportional to the relative amount of each substance in the organism mixture.

352
Q

Does tallest peak = most abundant substance
On a gas chromatogram

A

No
Not always
It’s about area

353
Q

The area under the peak of a GC chromatogram gives the relative amount of a substance
What would u need to find after

A

Conc

354
Q

What do you use to work out the concentration of a particular substance after GC

A

An external calibration curve

355
Q

How do you use an external calibration curve along with GC to find conc

A

1) create a series of standard solutions of differnt conc of analyte - thus us just the substance you’ve chosen to detect for your calibration
2) one by one, inject your standard solutions into a GC instrument and record the result
3) calculate area under the peak of each repsonse for each standard solution
4) plot these values on a graph of area vs concentration
5) join your pouts up to crest an external calibration curve

356
Q

Why would you run a blank when making a calibration curve
And what is a blank

A

A blank is a solution containing all the solvents and reagents used when making the standard solutions, but no analyste.
By subtractin the response of the blank form each of the responses of your standard solutions , you can find a corrected peak value - one that takes into account the fact of reagents and solvents on the peak area s

357
Q

What 3 factors effect retention time

A

Solubility
Boiling point
Temperature of the gas chromatography instrument

358
Q

How does solubility effect retention time

A

This determines how long each component of the mixture spends dissolved in the oil or on the solid and how long they spend morning along the tube in the gas. A highly soluble substance will spend more time dissolved, so will take longer to travel through the tube to the detector than one with a lower solubility .

359
Q

How does boiling point effect retention time

A

A substance with a high boiling point will spemd more time condensed as a liquid in the tube than as a gas. This means it will take longer to travel through the tube than one with a lower boiling point

360
Q

How does temperature of the gas chromatography instumsnt effect retention time

A

A high temperature means the substance will spend more time evaporated in the gas and so will move along the tube quickly, it shortens the retention time for all the substances in the tube

361
Q

What does ammino acid + hcl form

A

Ammonium salt + Cl-
(NH3+)

362
Q

What does amino acid + base form

A

H2O
Carboxylate salt
(Coo-)

363
Q

What is a zwitterion

A

The H from the COOH is internally transferred to the NH2
To form NH3+ and COO- ion
(It’s dipolar )

364
Q

What is the overall change of a zwitterion

A

0

365
Q

What is an Isoelectronic point

A

The PH at wich the zwitterion is formed

366
Q

Is the Isoelectronic point the same for all amino acids

A

No

367
Q

If the PH is less than the Isoelectronic point what happens

A

The amino acid will behave as a base and gain a proton
(From the zwitterion the coo- goes to COOH)

368
Q

What happens if the PH is greater than the Isoelectronic point

A

The amino acid will acid as an acid and will deprotenate
(From the zwitterion The NH3+ goes to NH2)

369
Q

Ensure you can identify an amide linkage

A

NC=O

370
Q

Check you can name amides

A
371
Q

What 3 ways can you prepare amides

A

From carboxylic acids
Acyl chlorides
Acid anhydrides

372
Q

How to prepare amides from carboxylic acids

A

CA + ammonium carbonate
Goes to ammonium carboxylate salt , co2 and H2O
Then from product dehydration/heat to. Amide + H2O

373
Q

What ammonium carboxylate salt is made from
CH3COOH + (NH4)2CO3

A

CH3COO-NH4+

374
Q

In preparation of CA, what needs to be in excess
And why

A

The CA
as RCOONH4 dissociates into RCOOH + NH3
excess of RCOOH shifts equlibrium to the left so increases RCOONH4 so more amide made after dehydrated

375
Q

Ensure you can prepare amides form acylchorides and acid anhydrides

A

( done in carbonyl topic)

376
Q

If you add sodium hydroxide solution to an unknown organic compound, and it gives off ammonia on heating, what is present

A

An amide

377
Q

What does NMR stand from

A

Nuclear magnetic resonance

378
Q

What is NMR

A

An analytical technique that you can use to work out the structure of an organic molecule

379
Q

What is the sample of a compound placed in during NMR

A

A strong magnetic field

380
Q

What is the sample exposed to in nmr

A

Range or differnt frequencies of radio waves

381
Q

What happens to the sample when exposed to differnt frequencies of radio waves

A

The nuclei of certain atoms within the molecule absorb energy from the radio waves

382
Q

The patter of the adsorption of radio waves from NMR, gives you what information

A

the position of certain atoms within the molecule and how many atoms of that type the molecule contains
You can peice this information together to work out the structure of the Molecule

383
Q

What are the 2 types of NMR

A

Carbon -13
high resolution proton

384
Q

What info does carbon-13 NMR give you

A

The number of carbon atoms that are in a molecule and the environments that they are in

385
Q

What info does high resolution proton NMR give you

A

The number of hydrogen atoms that are in a molecule and the environments that they are in

386
Q

What does an atoms environment depend on

A

all the groups that it’s connected to going right along the molecule - not just the atoms it’s actually bonded to

387
Q

What do 2 atoms need to be to be in exactly the same environment

A

Be joined to exactly the same thing

388
Q

How is a nucleolus partially shielded from external magnetic fields

A

By its surroundings electrons

389
Q

What effect the electron shielding of a nucleus

A

Any other atom or group of atoms that are around it
Eg. If a carbon atom is boned to an electronegative atom that amounts to other shielding around the nucleus will decrease

390
Q

Nuclei in a molecule feel differnt magenteic fields depending on their ……..
Nuclei in differnt …… will abosorb ……….. at ……..

A

Environment
Environments
Differnt amounts of energy
Differnt frequencies

391
Q

What are you looking at in NMR

A

The differnces in absorbtion of energy between environments

392
Q

How many carbon environments does chloroethane have and why

A

2 it’s carbons are bonded to differnt atoms

393
Q

How many carbon environments does 2-Chloro propane have

A

1 c in a CHCl group bonded to (CH3)2
2 C in CH3 bonded to CHCl(CH3)

394
Q

How many carbon environments do 1-chorlobutane have and why

A

4
The tow carbons in CH2 groups are differnt distances form the electronegative Cl atom so their environment is different

395
Q

What do3s each peak show and represent in a carbon-13 NMR spectrum

A

The peak shows the frequencies at which the energy was absorbed by the carbon nuclei
Each peak represents one carbon environment

396
Q

The differnces in absorbtion in carbon13 NMR spectrum are measured relative to what

A

A standard substance - TMS ( tetramethylsilane)

397
Q

Why does TMS produce a single absorbtion peak in both types of NMR

A

It’s carbon and hydrogen nuclei are in the same environment

398
Q

Why is TMS chosen as the standard

A

The absorbtion peak is at a lower frequency than just about Anything else

399
Q

What value is TMS given and how are other substances meausred relative to this

A

0
All the peaks in other substances are measured as chemical shifts relative to this

400
Q

What is a chemical shift

A

The difference in radio frequency absorbed by the nuclei ( hydrogen or carbon ) in the molecule that is being analysed and that is absorbed by the same nuclei in TMS

401
Q

What symbol is used for a chemical shift ( describe it ) and what are they measured in

A

The same symbol used to say partial charge like on a polar bond C=O for example

Parts per million or ppm

402
Q

Why would a small amount of TMS often be added to a sample

A

To give a reference peak on the spectrum,

403
Q

What is the chemical formula for TMS

A

Si(CH3)4

404
Q

What the first thing you should so when interpreting a carbon 13 spectra

A

Count the number of carbon environments

405
Q

How do you count the number of carbon environments on a carbon13 NMR spectra

A

Count the number of peaks
If there is a peak at 0 don’t count it it’s just the TMS reference peak

406
Q

If you have 3 carbon environments does that mean there are 3 carbons in your compound

A

No
Not necessarily there may be many carbons in the same environment

407
Q

After using the carbon13 NMR spectra to find number of carbon environments what should you do next

A

Look up the chemical shifts in a shift diagram

408
Q

What does the diagram on you data sheet for carbon13 NMR show

A

The chemical shifts experienced by carbon nuclei in differnt environments

409
Q

What does the step in carbon13 NMR spectra interpretation for looking up to chemcial shifts in a shift diagram involve

A

Match up peaks in the spectrum with the chemical shifts in the diagram to work out wich carbon environment they could represent .
A peak at 10 may repecent c-c and a peak at 25 may represent c-c in the same molecule, they are just in differnt environments

410
Q

Why is matching peaks to the groups in carbon13 NMR not always simple

A

Some chemcial shifts overall
So a peak at 40 for example could be due to c-c, c-Cl, c -br

411
Q

After looking up chemical shifts in a shift diagram when interpreting carbon13 NMR spectra what is the last step

A

Take into account carbon environments, mr and fg present and try possible structures

412
Q

What are optical isomers

A

Non superimposable mirror image of one another

413
Q

What is a carbon atom with 4 differnt groups attached called

A

Chiral or asymmetrical carbon

414
Q

What can 2 enantiomers of each other be called

A

+ -
D L
R S

415
Q

What is a 50/50 mixture of enantiomers called

A

Racemic or racemate

416
Q

How does Racemic mixture effect plane of polarised light

A

It has no overall effect

417
Q

What do 2 enantiomers have in common

A

Identical chemcial and physical properties

418
Q

What differs between enantiomers

A

Differnt effects on plane of polarised light
They have differnt reactions

A-level Chemistry <3 (9 decks)

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