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Chemistry Paper 2 > Module 6 > Flashcards

Module 6 Flashcards

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1
Q

Benzene is a carcinogen, what does this mean? (1 mark)

A

It causes cancer.

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2
Q

What is the prefix of benzene? (1 mark)

A

phenyl

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3
Q

Describe the Kekulé model of benzene. (2 marks)

A

Six carbon ring with alternate single and double bonds.

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4
Q

Explain how the lack of reactivity of benzene disproves Kekulé’s model of benzene. (3 marks)

A

Benzene should descolourise bromine water if it contains carbon double bonds.
However:
Benzene does not undergo electrophilic addition reactions.
Benzene does not decolourise bromine under normal conditions.

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5
Q

Explain how the lengths of the carbon-carbon bonds in benzene disprove Kekulé’s model of benzene. (2 marks)

A

All the bonds in benzene are the same length, between the lengths of a single and double bond.

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6
Q

How were the carbon-carbon bonds in benzene measured? (1 mark)

A

Using X-ray diffraction

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7
Q

Explain how hydrogenation enthalpies can be used to disprove Kekulé’s model of benzene. (3 marks)

A

The expected enthalpy change of hydrogenation is 3 times that of cyclohexene (as it has 1 double bond and benzene has 3).
In reality, the hydrogenation of benzene is lower than expected.
This means that benzene is more stable than the Kekulé model suggests.

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8
Q

Describe the delocalised model of benzene. (2 marks)

A

Each carbon atom has one electron in a p-orbital.
There is a delocalised pi-electron density above and below the plan of benzene ring.

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9
Q

How are the rings of electron density formed above and below the benzene ring plane? (1 mark)

A

Adjacent p-orbital electrons overlap sideways.

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10
Q

What does it mean if benzene is monosubstituted? (1 mark)

A

Only one hydrogen in benzene has been substituted for a different atom/group.

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11
Q

When is the prefix for benzene used? (1 mark)

A

When benzene is attached to a carbon chain of 7 or more.
When it is attached to an alkyl chain with a functional group.

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12
Q

Name three exceptions to naming aromatic compounds. (3 marks)

A

Benzoic acid
Phenylamine
Benzaldehyde

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13
Q

Are compounds that contain delocalised electrons more or less stable than those that don’t? (1 mark)

A

More stable.

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14
Q

Does benzene undergo electrophilic substitution? (1 mark)

A

Yes

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15
Q

What is the catalyst for the nitration of benzene? (1 mark)

A

Concentrated H2SO4

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16
Q

What reagents are in the nitrating mixture used to nitrate benzene? (2 marks)

A

Concentrated HNO3
Concentrated H2SO4

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17
Q

What temperature should the nitration of benzene take place at? (1 mark)

A

50 degrees

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18
Q

What happens if the temperature goes above 50 degrees when nitrating benzene? (1 mark)

A

Further substitutions take place, to produce dinitrobenzene.

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19
Q

(if have paper)
Draw the mechanism of the nitration of benzene. (5 marks)

A
  1. Equation(s) to show the production of nitrite ion.
  2. Curly arrow from ring to nitrite ion.
  3. Arrow from bond that links hydrogen to ring in intermediate.
  4. The ring doesn’t go past carbons 2 and 6 in intermediate.
  5. Correct products and regeneration of sulfuric acid.
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20
Q

What do halogens need to react with benzene? (1 mark)

A

A catalyst called a halogen carrier.

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21
Q

What are the reagents and conditions for the bromination of benzene? (2 marks)

A

RTP
React with AlBr3 or FeBr3

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22
Q

What are the products of the bromination of benzene? (1 mark)

A

Bromobenzene
Hydrogen bromide

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23
Q

(if have paper)
Draw the mechanism of the chlorination of benzene. (5 marks)

A
  1. Equation(s) to show the production of chlorine ion (with 1+ charge).
  2. Curly arrow from ring to chlorine ion.
  3. Arrow from bond that links hydrogen to ring in intermediate.
  4. The ring doesn’t go past carbons 2 and 6 in intermediate.
  5. Correct products and regeneration of FeCl3/AlCl3.
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24
Q

What is alkylation? (1 mark)

A

The addition of an alkyl group (contains C and H, with single C bonds).

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25
Q

What does benzene react with to produce an alkylbenzene? (1 mark)

A

A haloalkane.

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26
Q

What is the catalyst used in the alkylation of benzene? (1 mark)

A

AlCl3

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27
Q

(if have paper)
Draw the mechanism to produce ethylbenzene. (5 marks)

A
  1. Equation(s) to show the production of electrophile ion (with 1+ charge), from chloroethane and AlCl3.
  2. Curly arrow from ring to electrophile.
  3. Arrow from bond that links hydrogen to ring in intermediate.
  4. The ring doesn’t go past carbons 2 and 6 in intermediate.
  5. Correct products and regeneration of AlCl3.
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28
Q

What is acylation? (1 mark)

A

The addition of an acyl group (R-C=O).

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29
Q

What does benzene react with to produce an aromatic ketone? (1 mark)

A

Acylchloride

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30
Q

What is the catalyst used in the acylation of benzene? (1 mark)

A

AlCl3

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31
Q

(if have paper)
Draw the mechanism to produce phenylpropanone. (5 marks)

A
  1. Equation(s) to show the production of electrophile ion (with 1+ charge), from propanoylchloride and AlCl3.
  2. Curly arrow from ring to electrophile.
  3. Arrow from bond that links hydrogen to ring in intermediate.
  4. The ring doesn’t go past carbons 2 and 6 in intermediate.
  5. Correct products and regeneration of AlCl3.
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32
Q

Why does benzene need a halogen carrier catalyst to react with bromine, but an alkene doesn’t? (3 marks)

A

Benzene has delocalised electrons spread above and below the plane.
This means the electron density around any 2 carbons in a benzene ring is less than a C=C bond in an alkene.
So when a non-polar molecule, like bromine, approaches benzene there is insufficient pi-electron density to polarise the molecule.

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33
Q

What are the reagents and conditions of the alkylation of benzene? (2 marks)

A

Haloalkane
AlCl3
Reflux

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34
Q

What are the reagents and conditions of the acylation of benzene? (3 marks)

A

Acylchloride
Anhydrous conditions
AlCl3
Reflux

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35
Q

How does an alkene decolourise bromine water?

A

By electrophilic addition.

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36
Q

What is a phenol? (1 mark)

A

An organic compound that contains a hydroxyl group bonded to an aromatic ring.

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37
Q

Why are phenols less soluble in water than alcohols? (1 mark)

A

Because of the presence of the non-polar benzene ring.

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38
Q

What do phenols partially dissociate into in water? (1 mark)

A

A phenoxide ion and a proton.

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39
Q

Do phenols react with sodium hydroxide? (1 mark)

A

Yes

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40
Q

What is produced when phenol and sodium hydroxide react? (2 marks)

A

Sodium phenoxide
Water

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41
Q

Draw sodium phenoxide. (1 mark)

A

Look it up

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42
Q

What is produced when phenol and bromine react? (2 marks)

A

2, 4, 6- tribromophenol
3HBr

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43
Q

What two products can be produced when phenol reacts with nitric acid? (2 marks)

A

2-nitrophenol
or
4-nitrophenol

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44
Q

What are the reagents and conditions for the nitration of phenol? (1 mark)

A

Dilute nitric acid
RTP

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45
Q

What are the reagents and conditions for the bromination of phenol? (1 mark)

A

Bromine water
RTP

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46
Q

Why is phenol more reactive than benzene? (4 marks)

A

The O in the OH groups contributes another lone pair of electrons
to the pi-system of phenol,
this increases the electron density of the molecule,
making it more susceptible to electrophilic attack.

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47
Q

What is observed when phenol reacts with bromine water? (1 mark)

A

A white precipitate is formed.

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48
Q

What is an activating group, in aromatic chemistry, and how do they work? (4 marks)

A

Is electron donating,
and makes the aromatic ring more susceptible to electrophilic attack,
by increasing the electron density in the benzene ring
at positions 2, 4, and 6.

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49
Q

What is a deactivating group? (5 marks)

A

ls electron withdrawing
and makes the aromatic ring less susceptible to electrophilic attack,
by decreasing the electron density at positions 2, 4, and 6.
This means electrophiles are more likely to bond at carbons 3 and 5.

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50
Q

Why are deactivating groups 3-5 directing? (3 marks)

A

They withdraw electron density form the benzene ring,
decreasing electron density at positions 2, 4, and 6,
therefore electrophiles relatively more likely to bond to positions 3 and 5.

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51
Q

Why does chlorine react more readily with a C6H5N(CH3)2 than benzene? (3 marks)

A

Lone pair on nitrogen becomes partly dissociated into the pi bond system in benzene ring.
This causes the electron density to increase.
The benzene ring in the molecule has a greater ability to polarise the Cl-Cl bond.

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52
Q

What is an aldehyde? (1 mark)

A

The C=O group is at the end pf a carbon chain.

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53
Q

What is a ketone? (1 mark)

A

The C=O group is joined to two carbon atoms in the carbon chain.

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54
Q

How is the aldehyde group written in a structural formula? (1 mark)

A

CHO

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55
Q

How is the ketone group written in a structural formula? (1 mark)

A

CO

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56
Q

What is the ending (naming) for an aldehyde? (1 mark)

A

al

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57
Q

What is the ending (naming) for a ketone? (1 mark)

A

one

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58
Q

What aldehyde does the crested auklet bird release during breeding season? (1 mark)

A

Octanal

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59
Q

Do aldehydes undergo oxidation? (1 mark)

A

Yes

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60
Q

Do ketones undergo oxidation? (1 mark)

A

No

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61
Q

What are the reagents and conditions for the oxidation of an aldehyde? (2 marks)

A

Reflux
Potassium dichromate and sulfuric acid or acidified potassium dichromate

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62
Q

What is the product of an aldehyde being oxidised? (1 mark)

A

Carboxylic acid

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63
Q

Do aldehydes and ketones react with nucleophiles, why/why not? (2 marks)

A

Yes
The C=O bond is polar

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64
Q

What reduces aldehydes and ketones? (1 mark)

A

NaBH4 and water

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65
Q

What is a carbonyl compound? (1 mark)

A

A compound which contains a C=O functional group- aldehydes and ketones.

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66
Q

What are aldehydes reduced to? (1 mark)

A

Primary alcohols

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67
Q

What are ketones reduced to? (1 mark)

A

Secondary alcohols

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68
Q

Draw the mechanism of the reaction of propanone with NaBH4 and water. (5 marks)

A
  1. Curly arrow from C=O bond to delta negative oxygen.
  2. Curly arrow from hydride ion (H-) to delta positive carbon.
  3. Curly arrow from negative oxygen to delta positive hydrogen in water in intermediate.
  4. Curly arrow from H-O bond to delta negative oxygen in water.
  5. Correct products, propan-2-ol and OH- ion.
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69
Q

What does the reaction of a carbonyl compound with hydrogen cyanide produce? (1 mark)

A

A hydroxynitrile

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70
Q

Draw the mechanism of the reaction of propanal with hydrogen cyanide. (4 marks)

A
  1. Curly arrow from C=O bond to delta negative oxygen.
  2. Curly arrow from cyanide ion (-CN) to delta positive carbon.
  3. Curly arrow from negative oxygen to positive hydrogen ion.
  4. Correct product, 2-hydroxybutanenitrile.
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71
Q

What is a nucleophile? (1 mark)

A

An electron pair donor.

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72
Q

What does 2,4-DNP short for? (2 marks)

A

2,4- dinitrophenylhydrazine

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73
Q

What is 2,4-DNP used for? (1 mark)

A

To detect the presence of the carbonyl functional groups.

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74
Q

What is a positive result for a carbonyl group, using 2,4,-DNP? (1 mark)

A

Orange precipitate is formed.

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75
Q

Describe the test for aldehydes/ketones. (2 marks)

A

Add 2,4-DNP and a few drops of sulfuric acid/methanol.
Positive result: orange precipitate formed.

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76
Q

What is Tollen’s reagent used for? (1 mark)

A

To test for an aldehyde.

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77
Q

What is the result an aldehyde gives for Tollen’s test? (1 mark)

A

Positive- silver mirror

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78
Q

How is Tollen’s reagent prepared? (3 marks)

A

Add sodium hydroxide to silver nitrate
until a brown precipitate forms.
Add dilute ammonia until the precipitate dissolves.

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79
Q

How can the result of the test for carbonyl compounds (2,4DNP) be used to identify the carbonyl compound? (2 marks)

A

Each precipitate produced has a different melting point,
this can be compared to the known melting points of the derivatives.

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80
Q

Are carboxylic acids soluble in water, why/why not? (2 marks)

A

Yes, because the C=O is polar.

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81
Q

Explain the trend in solubility of carboxylic acids. (2 marks)

A

As number of carbon sin chain increase, solubility decreases
because the non-polar chain has more of an effect on the overall polarity of the molecule.

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82
Q

What are dicarboxylic acids? (1 mark)

A

Carboxylic acids that contain two carboxyl groups.

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83
Q

What is the ending (name) of a dicarboxylic acid? (1 mark)

A

‘anedioic acid’

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84
Q

What is the ion formed from a carboxylic acid called? (1 mark)

A

carboxylate ion

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85
Q

Are the boiling points of carboxylic acids higher or lower than similar Mr alcohols? (1 mark)

A

Higher

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86
Q

Why are the boiling points of carboxylic acids higher than similar Mr alcohols? (3 marks)

A

Carboxylic acids can form 2 hydrogen bonds between molecules,
whereas alcohols can only form 1 hydrogen bond between molecules.
So more energy is required to overcome these forces.

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87
Q

Why are carboxylic acids acidic? (2 marks)

A

The acidic nature of carboxylic acids is due to the relatively high stability of the carboxylate anion which forms from the delocalisation of the negative charge.

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88
Q

Fill in the gap:
The more charge can be spread around, the more ___________ an ion becomes.

A

The more charge can be spread around, the more stable an ion becomes.

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89
Q

Why are alcohols not acidic? (2 marks)

A

They are very poor at losing H+ ions,
due to there being no way of delocalising the negative charge of the negative ion formed if an alcohol lost an H+ ion.

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90
Q

metal + carboxylic acid –>
(2 marks)

A

H2 and carboxylate salt

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91
Q

metal oxide + carboxylic acid –>
(2 marks)

A

water + carboxylate salt

92
Q

alkali + carboxylic acid –>
(2 marks)

A

water + carboxylate salt

93
Q

carbonate + carboxylic acid –>
(2 marks)

A

CO2 + water + carboxylate salt

94
Q

What is the functional group of an ester? (1 mark)

A

COO

95
Q

What is the functional group of an acyl chloride? (1 mark)

A

COCl

96
Q

What is the structural formula of ethanoic anydride? (2 marks)

A

(CH3CO)2O

97
Q

What is esterfication? (2 marks)

A

When alcohol and a carboxylic acid react to produce an ester and water.

98
Q

What is produced when an acyl chloride and alcohol react? (2 marks)

A

An ester and HCl

99
Q

What is produced when an acid anhydride and alcohol react? (2 marks)

A

An ester and a carboxylic acid.

100
Q

What is produced when an acyl chloride and phenol react? (2 marks)

A

A phenyl ester and HCl

101
Q

How are acid anhydrides formed? (2 marks)

A

Condensation reaction
between 2 carboxylic acid molecules.

102
Q

What are the reagents and conditions for esterification? (2 marks)

A

alcohol is warmed
sulfuric acid catalyst

103
Q

Esters can be hydrolysed by an aqueous _____ or a ______.
(1 mark)

A

Acid or a base

104
Q

____________ hydrolysis is the opposite of esterification.
(1 mark)

A

Acid hydrolysis is the opposite of esterification.

105
Q

What are the reagents and conditions for the acid hydrolysis of an ester? (2 marks)

A

reflux
dilute aqueous acid

106
Q

What is the equation or the acid hydrolysis of an ester? (3 marks)

A

ester + water –> carboxylic acid + alcohol

107
Q

Is acid hydrolysis reversible? (1 mark)

A

yes

108
Q

Is alkaline hydrolysis reversible? (1 mark)

A

no

109
Q

What are the reagents and conditions for the alkaline hydrolysis of an ester? (2 marks)

A

reflux
aqueous alkali

110
Q

What is the equation or the alkaline hydrolysis of an ester? (3 marks)

A

ester + OH- –> carboxylate ion + alcohol

111
Q

What is the chemical formula of thionyl chloride? (1 mark)

A

SOCl2

112
Q

Describe how an acyl chloride is prepared. (3 marks)

A

Carboxylic acid is reacted with thionyl chloride
to produce an acyl chloride, sulfur dioxide, and hydrochloric acid.
Fractional distillation is used to separate the acyl chloride from any excess acid or thionyl chloride.

113
Q

Once a carboxylic acid has reacted with thionyl chloride, how is the acyl chloride separated from the other products? (1 mark)

A

Fractional distillation

114
Q

What is produced when an acyl chloride and water react? (2 marks)

A

Carboxylic acid and HCl

115
Q

Why must acylation reactions of acyl chlorides be carried out in anhydrous conditions? (2 marks)

A

Acyl chlorides react vigorously with water
releasing HCl fumes, which are corrosive/toxic.

116
Q

What is produced when an acyl chloride reacts with ammonia? (2 marks)

A

Primary amide
Ammonium chloride

117
Q

What is produced when an acyl chloride reacts with an amine? (2 marks)

A

Secondary amide
An ammonium chloride compound

118
Q

What two things can react with acyl chloride to produce an amide? (2 marks)

A

Ammonia
An amine

119
Q

What is produced when an acid anhydride reacts with a phenol? (2 marks)

A

A phenyl ester and carboxylic acid

120
Q

Draw the mechanism of the reaction between ethanoyl chloride and methylamine. (8 marks)

A

Step 1:
1. Curly arrow from lone pair on methylamine to carbon in ethanoyl chloride
2. Curly arrow from double bond to oxygen o oxygen
Step 2:
3. Correct intermediate with positive N
4. Curly arrow from bond to chlorine to chlorine
5. Curly arrow from negative oxygen to bond, reforming the double bond
Step 3:
6. Curly arrow from hydrogen on N to N
7. Curly arrow from a second methylamine molecule to hydrogen ion
Step 4:
8. Correct products:
CH3CONHCH3 and CH3NH3+ Cl-

121
Q

Describe how ethyl propanoate is prepared. (4 marks)

A
  1. Add ethanol and propanoic acid to boiling tube
  2. Add few drops of concentrated sulfuric acid
  3. Heat under reflux
  4. Add sodium carbonate solution
122
Q

What are the reagents and conditions for an alcohol and an acid anhydride to react? (2 marks)

A

Heated under reflux
Anhydrous conditions

123
Q

What are the reagents and conditions for an alcohol an acyl chloride to react? (2 marks)

A

RTP
anhydrous conditions

124
Q

What is used to purify an ester after it has been produced, how does it purify it? (2 marks)

A

Calcium carbonate, removes traces of alcohol.

125
Q

What is the function of sodium carbonate solution in the preparation of an ester? (2 marks)

A

It reacts with the traces of sulfuric acid and alcohol, neutralising them to produce water and soluble salts.

126
Q

What is optical isomerism? (1 mark)

A

When the mirror images of molecules are non-superimposable.

127
Q

What is a chiral carbon atom? (1 mark)

A

A carbon atom that has four different groups attached to it.

128
Q

What are two compounds that are optical isomers of each other called? (1 mark)

A

Enantiomers

129
Q

What is a 50/50 mixture of two enantiomers called? (1 mark)

A

A racemic mixture/ racemate

130
Q

What is the main difference between optical isomers? (1 mark)

A

They affect plane polarised light differently.

131
Q

Why does a racemate have no effect on the plane of light? (1 mark)

A

Each enantiomer rotates the plane polarised light by the same amount, but in the opposite direction.
This means the effects of the enantiomers cancel out.

132
Q

What is the functional group of an amine? (1 mark)

A

NH2

133
Q

What are amines derived from? (1 mark)

A

Ammonia

134
Q

What are the two types of amines? (2 marks)

A

Aliphatic amine
Aromatic amine

135
Q

What is an aliphatic amine? (1 mark)

A

The nitrogen atom is attached to at least one carbon chain.

136
Q

What is an aromatic amine? (1 mark)

A

The nitrogen atom is attached to an aromatic ring.

137
Q

What is a primary amine? (1 mark)

A

The nitrogen is attached to one a carbon chain.

138
Q

What is a secondary amine? (2 marks)

A

The nitrogen is attached to 2 carbon chains.

139
Q

What is the tertiary amine? (3 marks)

A

The nitrogen is attached to 3 carbon chains.

140
Q

How do you name secondary/tertiary amines? (2 marks)

A

Call it an N-substituted derivative of the larger group.

141
Q

What is serotonin? (2 marks)

A

An amine that acts as a neurotransmitter, controlling sleep, appetite, memory and many other things.

142
Q

What is pseudoephedrin? (2 marks)

A

An amine that is used in decongestion medications.

143
Q

Why do amines act as bases in chemical reactions? (1 mark)

A

They have a lone pair of electrons on the N that can accept a proton.

144
Q

What is the name of an amine ion? (1 mark)

A

ammonium ion

145
Q

How do amines react with acids? (1 mark)

A

Amines neutralise amines to make salts.

146
Q

How do you prepare a primary aliphatic amine, using a haloalkane? (3 marks)

A

Ammonia + haloalkane–> Ammonium salt
Ammonium salt + alkali (aq) –> amine

147
Q

What are the conditions required to prepare an aliphatic amine from a haloalkane, and explain why they are used? (4 marks)

A

ethanol- prevents substitution of haloalkane by water to produce alcohols
excess ammonia- reduces further substitution

148
Q

How do you prepare a secondary/tertiary amine, using a haloalkane? (2 marks)

A

Prepare a primary amine
Primary amine + haloalkane –> ammonium salt
ammonium salt + alkali (aq) –> amine

149
Q

How do you prepare an aromatic amine? (3 marks)

A

Reduction of nitrobenzene- heated under reflux with tin and HCl
Add excess NaOH

150
Q

What functional groups do amino acids contain? (2 marks)

A

NH2
COOH

151
Q

How do amino acids react with acids? (2 marks)

A

The amine group is basic, and react with acids to make salts.

152
Q

How do amino acids react with aqueous alkalis? (2 marks)

A

The carboxylic acid group reacts with the alkali to form a salt.

153
Q

How do amino acids react with alcohols? (2 marks)

A

The carboxylic acid group reacts with the alcohol to form an ester.

154
Q

What are the conditions required to form an ester from an amino acid? (2 marks)

A

heating
alcohol
concentrated sulfuric acid

155
Q

What are amides the products of? (2 marks)

A

acyl chloride + ammonia/amines

156
Q

What is the functional group of an amide? (2 marks)

A

Carbonyl group bonded to a nitrogen.
CON or CONH or CONH2

157
Q

What is a primary amide? (1 mark)

A

The nitrogen is attached to one a carbon chain.

158
Q

What is a secondary amide? (1 mark)

A

The nitrogen is attached to two carbon chains.

159
Q

What is a tertiary amide? (1 mark)

A

The nitrogen is attached to three carbon chains.

160
Q

Do amines have hydrogen bonds between molecules, why/why not? (2 marks)

A

Yes, they contain N-H bonds.

161
Q

Explain why a tertiary amine has a much lower boiling point than primary and secondary amines of similar Mr. (2 marks)

A

They have no hydrogen atoms directly attached to the nitrogen, so hydrogen bonding cannot happen between molecules.

162
Q

What is trend in solubility of amines as their caron chains get longer, why? (2 marks)

A

Less soluble as carbon chains increase in length,
because they force their way between water molecules, breaking the hydrogen bonds between water molecules and nitrogens in amines.

163
Q

Draw the mechanism of the production of an amine from a haloalkane. (6 marks)

A

Step 1:
1. Curly arrow from ammonia to carbon bonded to halogen in haloalkane
2. Curly arrow from bond C-halogen bond to halogen
Step 2:
3. Ammonia is now bonded to carbon chain from haloalkane in intermediate
4. Curly arrow from N-H bond to N+
5. Curly arrow from released another ammonia molecule to hydrogen
6. Correct product

164
Q

Describe how an amine is produced by the reduction of a nitrile compound, in a lab, include the reagents and conditions. (4 marks)

A
  1. haloalkane + KCN –> nitrile compound
  2. nitrile compound + 4[H] –> amine
    LiAlH4 in ethoxyethane
165
Q

Describe how an amine is produced by the reduction of a nitrile compound, in industry, include the reagents and conditions. (4 marks)

A
  1. haloalkane + KCN –> nitrile compound
  2. nitrile compound + 2H2 –> amine
    Ni catalyst + heat
166
Q

Why is phenylamine a weaker base than ammonia? (2 marks)

A

The lone pair of electrons on the nitrogen of the phenylamine is delocalised into the benzene ring,
making it less available to combine with hydrogen ions.

167
Q

What zwitterton does an amino acid exist as at a low pH? (1 mark)

A

The NH2 group is protonated to NH3+

168
Q

What zwitterton does an amino acid exist as at a neutral pH? (2 marks)

A

The NH2 group is protonated to NH3+
The COOH group is unprotonated to COO-

169
Q

What zwitterton does an amino acid exist as at a high pH? (1 mark)

A

The COOH group is unprotonated to COO-

170
Q

What is condensation polymerisation? (1 mark)

A

The joining of monomers with the loss of a small molecule (usually H20/HCl)

171
Q

What links the monomers in polyesters? (1 mark)

A

Ester linkages

172
Q

What functional groups must a monomer contain to turn a polyester by condensation polymerisation? (2 marks)

A

COOH and OH

173
Q

A polyester is made of two monomers, what functional groups must each monomer contain? (2 marks)

A

One contains 2 COOH groups
One contains 2 OH groups

174
Q

What is lactic acid derived from? (1 mark)

A

Maize

175
Q

Give an example of a polyester formed from one monomer. (1 mark)

A

Poly (lactic acid)
Poly (glycolic acid)

176
Q

Give an example of a polyester formed from two monomers. (1 mark)

A

Treylene (PET)

177
Q

What links the monomers in polyamides? (1 mark)

A

Amide linkages

178
Q

What functional groups must a monomer contain to turn a polyamide by condensation polymerisation? (2 marks)

A

COOH/COCl and NH2

179
Q

A polyamide is made of two monomers, what functional groups must each monomer contain? (2 marks)

A

One contains 2 COOH/COCl groups
One contains 2 NH2 groups

180
Q

What type of polymer do amino acids form, why? (2 marks)

A

Polyamide
Contain a COOH and a NH2

181
Q

How are condensation polymers hydrolysed? (1 mark)

A

Using an aqueous, hot acid/alkali

182
Q

What is formed when a polyester undergoes acid hydrolysis? (2 marks)

A

Alcohol
Carboxylic acid

183
Q

What is formed when a polyester undergoes alkali hydrolysis? (2 marks)

A

Alcohol
A carboxylic salt

184
Q

What is formed when a polyamide undergoes acid hydrolysis? (2 marks)

A

Carboxylic acid
Ammonium ion

185
Q

What is formed when a polyamide undergoes alkali hydrolysis? (2 marks)

A

Amine
A carboxylic salt

186
Q

Why are condensation polymers biodegradable? (2 marks)

A

Because contain C-O or C-N polar bonds in the main chain, which are susceptible to chemical attack.

187
Q

What are the strongest forces between polymer chains in addition polymers? (1 mark)

A

Induced dipole-dipole interactions

188
Q

What are the strongest forces between polymer chains in polyesters? (1 mark)

A

Permanent dipole-dipole interactions

189
Q

What are the strongest forces between polymer chains in polyamides? (1 mark)

A

Hydrogen bonds

190
Q

Haloalkane + NaCN –>

A

Nitrile + X-

191
Q

Haloalkane + NaCN –>

A

Nitrile + X-

192
Q

Aldehyde + HCN –>

A

Nitrile + OH-

193
Q

Ketone + HCN –>

A

Nitrile + OH-

194
Q

What does the reduction of a nitrile make?

A

Amine

195
Q

What does the hydrolysis of a nitrile make?

A

Carboxylic acid

196
Q

What is used in the reduction of nitriles?

A

H2 + Ni catalyst

197
Q

What is used in the hydrolysis of nitriles?

A

Heating with dilute (aq) acid

198
Q

How do you prepare a solid from a liquid reaction mixture? (4 marks)

A
  • Set up Buchner pressure apparatus
  • Put filter paper inside the funnel, and wet with solvent
  • Pour reaction mixture into funnel
  • Rinse beaker and add too
  • Leave under suction for a few minutes to dry
199
Q

Describe how you would recrystallise an impure solid to increase purity? (3 marks)

A
  • Dissolve the impure sample in a minimum volume of warm solvent
  • Allow solution to cool to room temperature, then place in a water bath until crystals reform
  • Filter using Buchner apparatus
200
Q

How do you evaluate the purity of the sample from its melting point range?

A

Pure samples have a very small melting range.

201
Q

How do you determine the melting point range of a sample? (3 marks)

A
  • Seal the end of a capillary tube using a Bunsen burner
  • Fill with crystals to about 3mm depth
  • Use electrically heated melting point apparatus to take its melting point
202
Q

What are two benefits of using reflux?

A

Speeds up the reaction.
Prevents reagents being lost.

203
Q

What method should be used to separate soluble and insoluble products?

A

-Add mixture to separating funnel
- Add water, shake
- Let settle
- If could contain trace amounts of acid, add NaHCO3
- Run off lower layer
- Add anhydrous CaCl2 to organic layer (drying agent)

204
Q

What is gas chromatography (GC) used for?

A

To separate volatile liquids.

205
Q

What happens in gas chromatography (GC)?

A
  • A small amount of the volatile mixture is injected into the apparatus
  • The mobile carrier gas carries the components through the column (inside a thermostatically controlled oven) where it separates into different liquids
  • Slower it moves–> greater affinity with stationary phase
  • Produces a chromatagram
206
Q

What is the mobile phase of GC?

A

An inert gas (e.g. nitrogen)

207
Q

Wat is the stationary phase of GC?

A

Solid/ high boiling point liquid coated on a solid support

208
Q

What do the number of peaks on a GC chromatogram represent?

A

The number of substances in the mixture.

209
Q

What does the area under each peak represent on a GC chromatogram?

A

The relative amount of the substance in the mixture

210
Q

What is the test for an alkene?

A

Add bromine water
Orange –> colourless

211
Q

What is the test for the halogens?

A

Add silver nitrate and ethanol at 50 degrees
Chloro- white
Bromo- Cream
Iodo- Yellow

212
Q

What is the test for a carbonyl group?

A

Add 2,4-DNP
Orange precipitate

213
Q

What is the test for an aldehyde group?

A

Add Tollens reagent + warm
Silver mirror

214
Q

What is the test for a primary/secondary alcohol?

A

Add K2Cr2O7 + warm
Orange –> Green

215
Q

What is the test for a carboxylic acid?

A

Add NaCO3 (aq)
Fizzing

216
Q

What is the test for a phenol?

A

Bromine water
White precipitate

217
Q

What is resonance?

A

When the nucleus can absorb energy and rapidly flip between the two spin states.

218
Q

What is used in a NMR spectrometer?

A

A super-conducting electromagnet, cooled by liquid helium.

219
Q

What is chemical shift in NMR?

A

When the electrons in atoms shift the energy and radio frequency needed for NMR.

220
Q

What is the unit for chemical shift?

A

ppm

221
Q

What substance is used as a standard reference in NMR?

A

TMS- has a chemical shift of 0ppm

222
Q

What happens when deuterium oxide is added to a H NMR spectrum reading, and why?

A

Any O-H or N-H peaks disappear, because the hydrogen gets replaced by a D, meaning it isn’t detected.

223
Q

What do the areas under a proton NMR spectra tell us?

A

The relative number of each type of proton.

224
Q

What is the splitting rule in proton NMR?

A

For a proton with n protons attached to an adjacent carbon atom, the number of sub-peaks in a splitting pattern is n+1.

225
Q

What is the chemical environment of a carbon determined by?

A

The position of the atom within the molecule and symmetry.

Chemistry Paper 2 (2 decks)

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