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OCR A Level Chemistry > Paper 3A Part 2 > Flashcards

Paper 3A Part 2 Flashcards

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1
Q

.If the compound doesn’t have a OH bond directly but still has an OH group it is classed as an ______, not a ______

A

alcohol, not a phenol

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2
Q

.Phenol is less soluble in water than alcohols, why?

A

due to its non-polar benzene ring

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3
Q

When dissolved in water, phenol partially dissociates to form what?

A

a phenoxide ion and a proton

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4
Q

As phenol only partially dissociates it is ______, other phenols also act as ________

A

a weak acid (pH4-6)weak acids

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5
Q

.Ethanol doesn’t react with sodium hydroxide (strong ___) or sodium carbonate (weak ___)

A

basebase

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6
Q

Phenols and carboxylic acids will react with ____________________ (like aqueous sodium hydroxide)

A

solutions of strong bases

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7
Q

carboxylic acids are strong enough to react with a weak base like sodium carbonate, you would observe what?

A

a gas/bubbles

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8
Q

Draw the mechanism for phenol and sodium hydroxide

A

check notes or internet

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9
Q

Draw the mechanism for phenol and sodium

A

check notes or internet

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10
Q

Describe the bromination of phenols?

A

.Phenol reacts with aqueous solution of bromine (bromine water) .A halogen carrier is not required and the reaction can be carried out at room temperature

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11
Q

Draw the mechanism of phenol and Br2

A

Check notes or internet

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12
Q

What does the bromination of phenol look like?

A

This reaction decolourises bromine water and forms a white precipitate

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13
Q

Why does phenol react more readily with bromine than benzene?

A

.One of the lone pairs of electrons on the p orbital of the O atom in the OH is partially delocalised into the ring.This increases the electron density.The electrophile becomes more polarised

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14
Q

Describe the nitration of phenol

A

.Phenol readily reacts with dilute nitric acid at room temperature.It does not need halogen carrier.Makes with 2-nitrophenol or 4-nitrophenol and water

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15
Q

Draw the nitration of phenol mechanism

A

check notes or internet

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16
Q

Many aromatic compounds can undergo a second substitution, what is this called?

A

a di-substitution

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17
Q

What is the directing effect?

A

The presence of substituted groups on a benzene ring will have an effect on the substitution of further groups – this is known as the directing effect

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18
Q

Substituted groups can be classified by the effect they have on the electron density of the ring, what are the classifications?

A
  • Electron donating – increases the electron density- Withdrawing electrons – decrease electron density
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19
Q

What are electron donating substitition groups also known as, why?

A

.Side chains that increase electron density allow electrophiles to react faster than with benzene, so are ‘activating’ products

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20
Q

Give an example of an electron donating substitution group

A

.OH – O lone pair orbitals overlap with delocalised ring.NH2 – N lone pair orbitals overlap with delocalised ring

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21
Q

Where do electron donating groups promote substitution?

A

.They increase the electron density at positions 2, 4, and 6.So electrophiles are more likely to react at these positions.The group directs substitution to positions 2, 4, and 6.2, 4-directing.The weaker position at 3 and 5 are rarely substituted

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22
Q

What are electron withdrawing substitition groups also known as, why?

A

.Side chains that decrease electron density slow electrophile reactions compared to benzene, so are ‘deactivating’ groups

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23
Q

Give an example of an electron withdrawing substitution group

A

.NO2 – O is more electronegative, drawing electrons away from the delocalised ring

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24
Q

Where do electron withdrawing groups promote substitution?

A

.It withdraws electron density at position 2, 4, and 6 – meaning that electrophiles are unlikely to react at these positions.The group directs substitutes to position 3.3- directing.The weaker positions at 2 and 4 are rarely substituted

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25
Q

Where does NH2 direct?

A

2, 4

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26
Q

Where does OH direct?

A

2, 4

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27
Q

Where does OR direct?

A

2, 4

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28
Q

Where does F, CL, Br, and I direct?

A

2, 4

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29
Q

Where does R direct?

A

2, 4

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30
Q

Where does NO2 direct?

A

3

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31
Q

Where does COOH direct?

A

3

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32
Q

Where does CHO direct?

A

3

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33
Q

Where does COOR direct?

A

3

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34
Q

What is R?

A

An alkyl group

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35
Q

In a carbonyl group, what are the charges on the atoms?

A

The carbon is delta +The oxygen is delta –

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36
Q

What is a carbonyl group?

A

C double bonded to O

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37
Q

What are aldehydes?

A

C=O group at the end of the carbon chain

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38
Q

How are aldehydes named?

A

start from the aldehyde end, suffix ‘-al’

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39
Q

What are ketones?

A

C=O group somewhere along the carbon chain, never at the end

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40
Q

How are ketones named?

A

C=O carbon should have lowest possible number

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41
Q

Primary alcohols will oxidise to what?

A

aldehydes and carboxylic acids

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42
Q

What is needed to oxidise primary alcohols? What will be seen?

A

An oxidising agent, acidified potassium dichromate K2Cr2O7/H+, needs heat, colour change if there is a reaction to green

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43
Q

Forming Aldehydes , how?

A
  • Distillation- Only from primary alcohol- Product must be distilled off or it will oxidise further- Reaction mixture contains excess alcohol- Colour change from orange to green- Forms water
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44
Q

Forming Carboxylic Acids , how?

A
  • Reflux- From primary alcohol- Heated under reflux with excess of [O] – ensures reaction goes to completion- Colour change from orange to green- Doesn’t form water (unless from primary alcohol, but not if from aldehyde)
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45
Q

What is benzene called when it has a ketone group attached to carbon 1?

A

Phenyl ethanone

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46
Q

What is benzene called when it has an aldehyde group attached to carbon 1?

A

Phenyl methanal

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47
Q

Secondary alcohols will oxidise to what?

A

Ketones

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48
Q

Conditions for oxidation of secondary alcohols

A

an oxidising agent, acidified potassium dichromate- Heated under reflux with excess of [O], ensures reaction goes to completion- Colour change from orange to green

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49
Q

What do tertiary alcohols oxidise to?

A

Tertiary alcohols don’t oxidise at all

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50
Q

Draw the product of the oxidation of propan-2-ol

A

check notes

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51
Q

Conditions for reduction of aldehydes and ketones?

A

Reduction – - Needs a reducing agent, NaBH4/H2O (sodium tetrahydridoborate)- Contains BH4- ions which is a source of H- ions• Need to warm it using water or ethanol as a solvent

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52
Q

What is a H- ion called?

A

A hydride ion

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53
Q

• Aldehydes and ketones can be reduced to their respective alcohols using what?

A

the reducing agent NaBH4

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54
Q

If reduced CH3CH2CHO, you would get what?

A

CH3CH2CH2OH

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55
Q

Reducing an aldehyde creates a what?

A

primary alcohol

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56
Q

Reducing a ketone creates a what?

A

Secondary alcohol

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57
Q

NaBH4 produces the nucleophile what?

A

H-hydride ion

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58
Q

Draw the equation for the reduction of CH3CH2CHO

A

check notes

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59
Q

Draw the equation for the reduction of CH3CH2COCH2CH3

A

Check notes

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60
Q

Draw the mechanism for the reduction of CH3CH2CHO

A

check notes

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61
Q

Hydrogen cyanide can be added across the C=O bond of which two functional groups?

A

aldehydes and ketones

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62
Q

What is hydrogen cyanide?

A

HCNa colourless and extremely poisonous liquid that cannot be safely used in labs

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63
Q

How is HCN used in labs? Why?

A
  • We use sodium cyanide and sulphuric acid to provide the hydrogen cyanide in the reactions- This makes it safer to carry out in a lab but it is still very dangerous
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64
Q

Why is the reaction of carbonyl compounds with HCN useful?

A

The reaction is very useful as it is a way of increasing the length of the carbon chain

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65
Q

How to name hydroxy nitriles

A
  • Need to include the carbon on the CN as part of the longest carbon chain’nitrile’ is the suffix
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66
Q

Draw the mechanism of the reduction of CH3CH2CH2CH2CHO

A

Check notes

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67
Q

Draw the mechanism of the reduction of CH3COCH3

A

check notes

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68
Q

Draw the equation for the reaction of CH3CH2CHO and HCN

A

Check notes

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69
Q

Draw the mechanism of the reaction of CH3CH2CHO and HCN

A

Check notes

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70
Q

Draw 2-hydroxybutanenitrile

A

check notes

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71
Q

What does tollens agent react with?

A
  • Tollens’ reagent oxidises aldehydes to carboxylic acids but does not oxidise ketones
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72
Q

How to form tollens agent

A
  • Tollens reagent = NaOH(aq) added to AgNO3 until a brown precipitate is formed, then add dilute NH3 until precipitate dissolves to form a colourless solution
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73
Q

What does a positive tollens agent test form

A

A silver mirror

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74
Q

WHat happens to silver ions in tollens test

A
  • Silver ions are reduced:o Ag+(aq) + e-  Ag(s¬)
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75
Q

Draw the general formula for tollens test

A

cHECK NOTES

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76
Q

WHat is used to test for carbonyl compounds?

A

2-4, dinitrophenylhydrazine (2, 4-DNP or brady’s reagent)

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77
Q

In the carbonyl compound test, how is brady’s agent used?

A

Is dissolved in methanol and sulfuric acid

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78
Q

What colour does brady’s agent turn?

A
  • Reacts with carbonyl groups to form a bright orange precipitate
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79
Q

WHat does brady’s agent react with?

A
  • It only happens for compounds with a C=O bond, so aldehydes and ketones- Doesn’t work for COOH or esters
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80
Q

WHat is the orange precipitate from Bradys agent?

A
  • The orange precipitate is derivative of a carbonyl compound and can be used to identify an unknown compound with a carbonyl group
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81
Q

The method for identifying a carbonyl compound using bradys agent

A
  1. You are given an unknown compound with a carbonyl group2. Add 2,4-DNP to see an orange precipitate formed that is a derivative of the carbonyl group3. Filter off the crystals using a Buchner funnel and water pumpThis is an impure solid you need to have a pure solid, so we need to purify and then recrystallize4. Dissolve the crystals in the smallest amount of hot solvent (ethanol) to purify and then put the test-tube in ice water to allow the pure solid to recrystallize5. Filter off the crystals again using a Buchner funnel and water pump, this time you have a pure solid6. Find the melting point of the pure solid7. Compare to a known database of melting points for carbonyl derivatives to identify carbonyl
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82
Q

Descibr carboxylic acids

A
  • A homologous series which contain the carboxyl functional group COOH- The bonds are in a planar arrangement- Include a carbonyl (C=O) group and a hydroxyl (O-H) group
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83
Q

How to name carboxylic acids

A
  • Select the longest chain of C atoms containing the COOH group- Remove the e and add oic acid after the basic name- Number the chain starting from the end nearer the COOH group- As in alkanes, prefix with alkyl substituents- Side chain positions are based on the C in COOH being 1
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84
Q

Why are carboxylic acids soluble in water?

A

Carboxylic acids are polar molecules, electrons are drawn towards the oxygen atoms.Hydrogen bonds form between the highly polarised hydrogen and oxygen atoms on the molecules.This makes them soluble in water.

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85
Q

As the carbon chain gets longer, carboxylic acids get less soluble, why?

A

this happens as the non-polar carbon chain having a greater effect on the overall polarity.

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86
Q

Acid + Metal –>

A

Salt and hydrogen

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87
Q

Acid + Metal Oxide –>

A

Salt and water

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88
Q

Acid + Alkali –>

A

salt and water

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89
Q

Acid + Metal Carbonate –>

A

Salt and water and carbon dioxide

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90
Q

2HCl(aq) + 2Na(aq) –>

A

2NaCl(aq) + H2(g)

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91
Q

2HCl(aq) + Na2O(s) –>

A

2NaCl(aq) + H2O(l)

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92
Q

HCl(aq) + NaOH(aq) –>

A

NaCl(aq) + H2O(l)

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93
Q

2HCl(aq) + Na2CO3(s) –>

A

2NaCl(aq) + H2O(l) + CO2(g)

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94
Q

Carboxylic acids are ___ acids and take place in ____ reactions with metals and _______ reactions with bases (alkali’s, metal oxides and metal carbonates).

A

weak redox neutralisation

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95
Q

In some reactions of carboxylic acids what is formed?

A

carboxylate salts

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96
Q

What is a carboxylate salt?

A

One of the ions formed in the salt is a carboxylate ion.

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97
Q

CH3COOH

A

CH3COO- + H+

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98
Q

Ethanoic acid

A

Ethanoate ion + Hydrogen ion

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99
Q

Name and give the structure of the 3 first carboxylate ions

A
  • Methanoate ion CHOO– Ethanoate ion CH3COO– Propanoate ion CH3CH¬2COO-
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100
Q

Benzene with a carboxylic acid group when ionised becomes what?

A

a Benzoate ion NOT a benzanoate ion

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101
Q

, Ethanoic acid + Sodium –>

A

Sodium ethanoate + Hydrogen

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102
Q

Ethanoic acid + sodium 

A

sodium ethanoate + hydrogen

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103
Q

Ethanol + sodium 

A

sodium ethoxide + hydrogen

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104
Q

Sodium ethanoate written structure

A

Na+CH3COO-

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105
Q

Sodium ethoxide writtren structure

A

C2H5O-Na+

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106
Q

A derivative of carboxylic acid is what?

A

a compound that can be hydrolysed to form the parent carboxylic acid it was formed form.

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107
Q

All carboxylic acid derivatives have a common sequence of atoms in their structure known as what?

A

an acyl group.

108
Q

Draw an acyl group

A

CHECK NOTES OR GOOGLE

109
Q

Draw an ester group

A

CHECK NOTES OR GOOGLE

110
Q

Draw an acyl chloride group

A

CHECK NOTES OR GOOGLE

111
Q

Draw an amide group

A

CHECK NOTES OR GOOGLE

112
Q

Draw an acid anhydride group

A

CHECK NOTES OR GOOGLE

113
Q

Draw Ethanoic acid + methanol 

A

CHeck NOTES OR GOOGLE

114
Q

What is esterfication?

A

This is a reaction where an alcohol and a carboxylic acid react together to form an ester and water. It is a condensation reaction.

115
Q

Reagents and conditions for esterfication?

A

Reagents: catalyst (concentration H2SO4)Conditions: warm

116
Q

Propanoic acid + ethanol 

A

ethyl propanoate + water

117
Q

What is special about esters?

A

Most esters have a pleasant odour.Depending on the alcohol and acid used, many different fragrances can be made.

118
Q

What is an acid anhydride?

A

An acid anhydride is formed when water is removed from two molecules of carboxylic acid.

119
Q

2 ethanoic acids form what when water is removed?

A

ethanoic anhydride

120
Q

How can you make an ester using an alcohol?

A

You can form an ester using acid anhydride and an alcohol.

121
Q

Acid anhydride + alcohol 

A

ester + carboxylic acid

122
Q

Ethanoic anhydride + methanol 

A

methyl ethanoate + ethanoic acid

123
Q

Draw ethanoic anhydride + methanol

A

check notes

124
Q

What is hydrolysis?

A

Hydrolysis is the chemical breakdown of a compound in the presence of water or in aqueous solution

125
Q

What are the two types of hydrolysis?

A

There are two types:1. Acid hydrolysis2. Alkaline hydrolysis

126
Q

Describe the process of acid hydrolysis

A
  • Heated under reflux with dilute aqueous acid- Ester broken down by water using the acid as a catalyst- Reversible reaction
127
Q

Finish the equationCH3COOCH3 + H2O HCl

A

CH3COOH + HOCH3

128
Q

Describe the process of alkaline hydrolysis

A
  • Reflux with aqueous alkali (NaOH or KOH)- Get a carboxylate salt and alcohol- Salt can be used to make soap – saponification- Irreversible
129
Q

Finish the equationCH3COOCH3 + NaOH 

A

CH3COONa + HOCH3

130
Q

Draw an acyl group

A

check notes or google

131
Q

Draw an acyl chloride

A

check notes or google

132
Q

How to name an acyl chloride group

A

The primary suffix name is based on the longest carbon chain name (minus ‘e’) + ‘oyl chloride’ for the COClThe carbon atoms are numbered from the C with the acyl functional group

133
Q

Draw propanoyl chloride

A

check notes or google

134
Q

Draw benzoyl chloride

A

check notes or google

135
Q

Amines can be classified as primary, secondary, and tertiary, how is this determined?

A

This is determined by the number of carbon alkyl (carbon chain) or aryl (benzene ring) attached to the N atom.

136
Q

Draw a primary amine

A

check notes or google

137
Q

Draw a secondary amine

A

check notes or google

138
Q

Draw a tertiary amine

A

check notes or google

139
Q

How to name amines

A

If the amine (NH2) group is on the end of the carbon chain, the suffix is amine. You add the suffix to the alkyl group.If the amine (NH2) group is on any other carbon chain except carbon 1, the prefix is amino. You need to give the position of the amine group.In secondary and tertiary amines that contain the same alkyl group you have a prefix di or tri.

140
Q

In secondary and tertiary amines that contain two or more different alkyl groupsThe compound is named as an what?

A

N-substituted derivative

141
Q

Draw N-methl propylamine

A

check notes

142
Q

Draw N-ethyl N-methyl propylamine

A

check notes

143
Q

Amides can be classified as primary, secondary, or tertiary, how is this determined?

A

This is determined by the number of carbon atoms attached to the N atom

144
Q

Draw a primary, tertiary and secondary aminde (using R)

A

check notes

145
Q

Formula of propanamide

A

CH3CH2CONH2

146
Q

Formula of benzamide

A

C6H5CONH2

147
Q

Formula of N-ethyl butanamide

A

CH3CH2CH2CONHCH2CH3

148
Q

Formula of N, N-dimethyl methanamide

A

CHON(CH3)CH3

149
Q

How are acyl chlorides made?

A

by reacting a carboxylic acid with thionyl chloride (SOCl2)

150
Q

CH3CH2COOH + SOCl2 

A

CH3CH2COCl + SO2 + HCl

151
Q

What would you see if HCl is produced as a product in carbonyl reactions?

A

Steamy white fumes

152
Q

Describe the reaction of acyl chloride and alcohols

A

With Alcohols to Form EstersThis is a vigorous reaction which happens at room temperature.

153
Q

Propanoyl chloride + propan-1-ol 

A

propyl propanoate + HCl

154
Q

Describe the reaction of acyl chloride and phenol

A

With phenol to form an aromatic esterEsters are formed again during the esterification reaction between phenol and an acyl chloridePhenol + acyl chloride ester + HCl

155
Q

Phenol + propanoyl chloride

A

phenyl propanoate + hydrogen chloride

156
Q

Describe the reaction of acyl chloride and water

A

With water to form carboxylic acidThis is a vigorous reaction with cold water

157
Q

Propanoyl chloride + water 

A

propanoic acid + hydrogen chloride

158
Q

Describe the reaction of acyl chloride and ammonia

A

With ammonia to form amidesThis is a violent reaction at room temperature to form a primary amide

159
Q

Propanoyl chloride + ammonia 

A

propenamide + ammonium chloride

160
Q

Describe the reaction of acyl chloride and amines

A

With amines to form amidesThis is a violent reaction at room temperature to form secondary amides

161
Q

Propanoyl chloride + methylamine 

A

N-methylpropanamide + methylammonium chloride

162
Q

Ester 1 ( C6H5COHCOOC(CH3)2 ) is less soluble than mandelic acid ( C6H5CH(OH)COOH ), why?

A

Hydrogen bonds are formed with water, between oxygen and hydrogen, mandelic acid has 2 OH groups (whilst ester 1 has 1), therefore more hydrogen bonds can be formed and so it is more soluble

163
Q

Define acid

A

Acid – In water, an acid releases hydrogen ions (H+) into solution

164
Q

Define base

A

Base – A base is a compound that neutralizes an acid, by accepting a hydrogen ion, to form a salt

165
Q

Define salt

A

Salt – A salt is the product of a reaction in which the H+ ions from the acid are replaced by the metal or ammonium ions

166
Q

HCl + OH-

A

H2O + Cl-

167
Q

Bases donates _ electrons to the hydrogen ion to form a ___ ___ bond, bases can either have a ___ ___ or a ____ ___.

A

2 dative covalentlone pairnegative charge

168
Q

How is ammonia a base?

A

Ammonia (NH3) is a base, it accepts a proton to become an ammonium ion.

169
Q

NH3 + HCl 

A

NH4Cl

170
Q

Amines behave as ___ in chemical reactions

A

bases

171
Q

How do amines behave as bases in chemical reactions?

A

The lone pair of electrons on the nitrogen accepts a proton (a hydrogen ion)A dative covalent bond is formed, they form an ammonium ion

172
Q

Ethylamine + H+ 

A

Ethylammonium ion

173
Q

CH3CH2NH2 + H+ 

A

CH3CH2NH3+

174
Q

Ethylamine + HCl 

A

Ethylammonium chloride

175
Q

CH3CH2NH2 + HCl 

A

CH3CH2NH3Cl

176
Q

The strength of a base depends on how available the nitrogen’s lone pairs of electrons is, how?

A

A lone pair of electrons are more available if its electron density is higherThe higher density, the more available the lone pair, the stronger the base

177
Q

How strong of a base are aromatic amines? Why?

A

For aromatic amines, the benzene ring pulls the electrons towards the delocalized ring, electron density increases, weak base

178
Q

How strong of a base is ammonia? Why?

A

For ammonia, it doesn’t have an aromatic group to pull the lone pair away or an alkyl group to push the lone pair of electrons forward, base

179
Q

How strong of a base are aliphatic amines? Why?

A

For aliphatic amines (RNH2), the alkyl group pushes the electrons forward, towards the nitrogen, so the electron density increases, and the lone pair is more available, strong base

180
Q

How to form primary aliphatic amines?

A
  1. Ammonia has a lone pair of electrons on the N atom which allows it to act as a nucleophile in a reaction with a haloalkane, the product of this reaction is an ammonium salt2. Aqeous alkali (NaOH) is added to generate the amine from the salt
181
Q

Conditions for formation of primary aliphatic amines

A

For this reaction to happen, the conditions needed are:- Excess NH3- Ethanol as a solvent to prevent substitution of the haloalkane by water to make an alcohol – also called ethanolic ammonia

182
Q

What are the equations for the formation of ethylamine, using 1-chloroethane?

A

CH3CH2Cl + NH3  CH3CH2NH3+Cl-1-chloroethane + ammonia  ethylammonium chloride CH3CH2NH3+Cl- + NaOH  CH3CH2NH2 + NaCl + H2OEthylammonium chloride + sodium hydroxide  ethylamine + sodium chloride + water

183
Q

How are secondary aliphatic amines formed?

A

The primary amine can react with the haloalkane to make a secondary amine.

184
Q

What are the equations for the formation of di-ethyl amine, using 1-chloroethane and ethylamine?

A

This is a two stage reaction:1. CH3CH2NH2 + CH3CH2Cl  (CH3CH2)2NH2+Cl-Ethyl amine + 1-chloroethane  Di-ethyl ammoniumchloride2. (CH3CH2)2NH2+Cl- + NaOH  (CH3CH2)2NH + NaCl + H2ODi-ethyl ammoniumchloride + sodium hydroxide  Di-ethyl amine + sodium chloride + water

185
Q

The secondary amine can react with the haloalkane to make a tertiary amine, what is the two step reaction for this? Using 1. (CH3CH2)2NH + CH3CH2Cl

A
  1. (CH3CH2)2NH + CH3CH2Cl  (CH3CH2)3NH+Cl-Secondary amine + haloalkane  salt (triethyl ammonium chloride)2. (CH3CH2)3NH+Cl- + NaOH  (CH3CH2)3N + H2O + NaClSalt + sodium hydroxide  tertiary amine + water + sodium chloride
186
Q

Draw the mechanism for CH3Cl + CH3CH2NH2

A

CHECK NOTES

187
Q

Phenylamine is made by the reduction of _____

A

nitrobenzene

188
Q

C6H5NO2  _____  C6H5NH2

A

reduction with concentrated HCl and Sn in reflux

189
Q

What is the two step reaction for the formation of phenylamine from nitrobenzene?

A
  1. C6H5NO2 + 7[H]  C6H5NH3+Cl- + 2H2ONitrobenzene + reducing agent  phenyl ammonium chloride (a salt) + water2. C6H5NH3+Cl- + NaOH  C6H5NH2 + NaCl + H2Ophenyl ammonium chloride (a salt) + sodium hydroxide  phenylamine + sodium chloride + water
190
Q

C6H5NO2 + 6[H] 

A

C6H5NH2 + 2H2O

191
Q

What are aminos?

A

Amino are organic compounds containing amine and carboxylic acid functional groups, the side R chain is specific to each amino acid

192
Q

Draw the general displayed formula for an amino acid

A

check notes

193
Q

What is the general written formula for amino acids?

A

RCH(NH2)COOH

194
Q

What are the three types of amino acids and how do they differ?

A
  • Alpha-amino acidso 2 carbons- Beta-amino acido 3 carbons- Gamma-amino acidso 4 carbons
195
Q

Write the formula for glycine and state its proper name

A

o HCH(NH2)COOHo Proper name is 2-amino ethanoic acid

196
Q

Write the formula for alanine and state its proper name

A

o H3CH(NH2)COOHo Proper name is 2-amino propanoic acid

197
Q

Write the formula for phenylalanine and state its proper name

A

o H5C6H2CCH(NH2)COOHo 2-amino, 3-phenyl propanoic acid

198
Q

How is an amino acid both a proton donor and acceptor?

A

Amino acids contain an acid group (COOH) and a base group (NH2)The COOH is a proton donor, and the NH2 is a proton acceptor

199
Q

As amion acids are both proton donors and acceptors, what can they do?

A

This means it can react with itself so the H+ ion from the COOH is donated to the NH2, this forms an ion called a zwitterion

200
Q

What is the charge on a zwitterion?

A

0

201
Q

Zwitterions only form at their specific isoelectric point, what is an isoelectric point?

A

pH at which an amino acid exists as a zwitterion

202
Q

What is the isoelectric point affected by?

A

Different R groups

203
Q

Draw the general formula for the formation of zwitterions

A

check notes

204
Q

Alanine’s isoelectric point is ?

A

pH 6.01

205
Q

Draw the formation of alanine’s zwitterion

A

check notes

206
Q

What happens to zwitterions in acidic conditions?

A

a lower pH, it is in acidic conditions, and so H+ ions are added wherever they can be

207
Q

What happens to zwitterions in basic conditions?

A

At pH 7.01, a higher pH, it is in alkaline conditions, and so H+ ions are removed wherever they can be

208
Q

Draw the product of an alanine zwitterion in acidic conditions

A

check notes

209
Q

Draw the product of an alanine zwitterion in basic conditions

A

check notes

210
Q

What is glutamic acid’s isoelectric point?

A

3.22 pH

211
Q

Draw the product of an glutamic acids zwitterion in basic conditions

A

Check notes

212
Q

Draw the product of an glutamic acids zwitterion in acidic conditions

A

Check notes

213
Q

What is lysine’s isoelectric point?

A

9.59pH

214
Q

Draw the product of an lysine’s zwitterion in acidic conditions

A

Check notes

215
Q

Draw the product of an lysineds zwitterion in basic conditions

A

check notes

216
Q

What’s the equation for alanine (R=CH3) and HCL?

A

H3CCH(NH2)COOH + HCl  CH3CH(N+H3)COOH Cl-

217
Q

What’s the equation for alanine (R=CH3) and NaOH?

A

CH3CH(NH2)COOH + NaOH  CH3CH(NH2)COO-Na+ + H2O

218
Q

What’s the equation for alanine (R=CH3) and methanol?

A

CH3CH(NH2)COOH + CH3OH  CH3CH(NH2)COOCH3 + H2O

219
Q

WHat are stereoisomers?

A

Stereoisomers are species with the same structure but a different arrangement of atoms in space

220
Q

WHich one of E-but-2-ene, and Z-but-2-ene is trans?

A

E-but-2-ene

221
Q

What is superimpose?

A

to place or lie over another and they are the same

222
Q

What does it mean if you can or cannot superimpose two molecules of the same structure?

A

If you can superimpose, they are identical, and cannot form an optical isomerIf you cannot superimpose, they are not identical, and can form an optical isomer

223
Q

When you have 4 different groups attached to a carbon, the molecule shows what?

A

optical isomerism

224
Q

WHat are chiral centres?

A

Carbon atoms with 4 different groups attached are called chiral centers

225
Q

Where does the word chiral come from?

A

Chiral is the Greek word for hands

226
Q

Draw 2-bromobutane and identify the chiral centre

A

check notes

227
Q

Draw 2, 3-dimethyl pentane and identify the chiral centre

A

check notes

228
Q

Draw chloroethanoic acid and identify the chiral centre

A

check notes (there is no chiral centre)

229
Q

How to draw optical isomerism?

A
  • Put chiral carbon in middle and draw groups off of it - Use wedges, dashes, and lines as usual- Draw it like a tetrahedron- Mirror it
230
Q

For a substance that can undergo optical isomerism, the different optical isomers are called what?

A

enantiomers

231
Q

What is a racemic mixture?

A

A racemic mixture is when you have a mixture of a substances enantiomers together.

232
Q

Draw the optical isomerism of CH3 C (OH) Cl

A

check notes

233
Q

If a molecule has 1 chiral center, there will be _ isomers.

A

2

234
Q

If a molecule has 2 chiral centers, there will be _ isomers.

A

4

235
Q

For every chiral center, there are ___ possible isomers.

A

two

236
Q

Draw the isomers of CH3 C (Cl) C (OH) Br

A

CHECK NOTES

237
Q

Explain how a time of flight spectrometer works

A
  1. injection2. vaporization3. ionisation chamber4. acceleration area5. drift region6. detector
238
Q

Describe and explain fragments in mass spectrometry

A
  • Excess energy from the ionization process can be transferred to the molecular ion and cause it to split (fragment)- When it fragments:o It produces a smaller positive ion and radicalo The smaller positive ion is detectedo Fragment ions can be broken down further still
239
Q

What does a CH bond do when it absorbs IR?

A

stretches

240
Q

What does a HCH bond do when it absorbs IR?

A

bends

241
Q

Each bond in IR spectroscopy vibrates with a unique freuquency, which is picked up by what?

A

the spectrometer

242
Q

What does vibration in IR spectroscopy depend on?

A
  • Bond strength- Bond length- Mass of the bonded atom
243
Q

What are the types of movement found in IR spectroscopy?

A
  • Symmetrical stretching- Antisymmetrical stretching- Scissoring- Rocking- Wagging- Twisting
244
Q

How to identify alcohols with IR spectorscopy?

A

Primary alcohol = 1050Secondary alcohol = 1100Tertiary alcohols = 1150OH bond = 3200-3640

245
Q

Mr of CH3+

A

15

246
Q

Mr of C2H5+

A

29

247
Q

Mr of C3H7+

A

43

248
Q

Mr of OH+

A

17

249
Q

Mr of C4H9+

A

57

250
Q

Equation of formation of C6H14+ in hexane mass spectrometry

A

C6H14  C6H14+ + e-

251
Q

Equation of formation of C4H9+ in hexane mass spectrometry

A

C6H14+  C4H9+ + •C2H5

252
Q

How to check for polarity on a molecule?

A

Ask the two questions:Are the surrounding atoms the same?Is there a long pair on the central atom?If the answer is yes to both its polar, if its no to both its polar, if its yes to one and no to the other its non-polar

253
Q

Rf =

A

distance of pigment / solvent front

254
Q

What does the Rf value tell you?

A

Generally if the Rf values are the same, they are the same substance (there are exceptions)

255
Q

Problems with Rf values

A
  • Components can have similar Rf values- The unknown substance is new and there is no previous chemical to compare it with
256
Q

What is Thin Layer Chromatography (TLC)?

A
  • TLC is very similar to paper chromatography- Rather than using chromatography/filter paper the stationary phase is a thin uniform layer (usually silica gel) coated on a piece of plastic, metal, or glass- The mobile phase is a liquid which acts as a solvent for the substances you are trying to separate or analyze
257
Q

Steps of TLC

A
  1. A base line is drawn in pencil across the plate and dots of the substances are placed along the line2. The plate is placed in a beaker of the solvent such that the level of the solvent is below the line and the solvent moves up the plate3. A lid is placed to ensure the atmosphere in the tank is saturated with the often volatile solvent which climbs up the plate causing the mixture to separate4. As the solvent front moves up the plate the mixture separates into its different components5. The solvent reaches near to the top of the plate and the plate is removed6. The solvent front is noted and the solvent is left to evaporate
258
Q

What happens if the substances are colorless in TLC?

A
  • Using UV Lighto The stationary phase has a chemical added to it which will fluorescence under UV light, the spots need to be circled while under the light- Chemicallyo The chromatogram is dried and sprayed with a ninhydrin spray, amino acids react and turn a purple/brown colouro You can also use iodine crystals, the chromatogram is dried and placed in an enclosed container with a few iodine crystals, the iodine vapor in the container may either react with the pots on the chromatogram, or simply stick more to the spots than to the rest of the plate, either way the substances you are interested in may show up as brownish spots
259
Q

How does TLC work?

A
  • Silica gel is a form of silicon dioxide (silica)- The silicon atoms are joined via oxygen atoms in a giant covalent structure- However, at the surface of the silica gel, the silicon atoms are attached to -OH groups- The surface of the silica gel is very polar and, because of the -OH groups, can form hydrogen bonds with suitable compounds around it as well as van der waals dispersion forces and dipole-dipole attractions- With a solid stationary phase, the pigments are adsorbed onto the surface of the solid particles or fibers- The relative forces of attraction between the stationary phase, the mobile phase, and the pigment mean that separation happens
260
Q

Define adsorption

A

Adsorption – is the adhesion of atoms, ions, or molecules from a gas, liquid, or dissolved solid to a surface

261
Q

Which pigments will move how much in TLC?

A
  • Insoluble pigmento Won’t move- Strong forces of adsorptiono More polar so won’t move a lot- Weak forces of adsorptiono Less polar so will move a lot
262
Q

When will the Rf value stay the same?

A
  • Providing the temperature, stationery phase, and solvent stay the same, the Rf value will stay the same on repeats
263
Q

What is Gas liquid chromatography?

A
  • In GLC a long column is often filled with a liquid compound- In thinner tubes, the stationary phase is coated to the inside surface of the tube- The sample is vaporized and pushed through the column by an inert carrier gas (most often nitrogen or helium)
264
Q

How does gas-liquid chromatography (GLC) work?

A
  • Depending on the solubility of the different compounds in the stationary liquid phase, their boiling points and the temperature of the column, the different compounds will travel through the GLC column at different speeds- The length of time a compound remains in the column is known as the retention time- It is calculated from the time the sample is injected until the maximum peak heigh for that compound is observed on the display/chromatogram- Compare to a known database to find the molecule
265
Q

Explain how to find the proportion of components in GLC?

A

The area under the peaks can be used to calculate the composition of the mixtureArea of triangle = ½ x base x heightWork out individual areas and add them togetherWork out percentage of area taken up by each peak

OCR A Level Chemistry (17 decks)

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