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Chemistry Paper 2 > Module 4 > Flashcards

Module 4 Flashcards

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1
Q

What is a hydrocarbon?

A

A molecule consisting of only carbon and hydrogen
Can be saturated or unsaturated

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2
Q

What is a homologous series?

A

A family of compounds with similar chemical properties
Where successive members differ by the addition of a CH2 group

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3
Q

What is the general formula of an alkane?

A

CnH2n+2

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4
Q

What is a functional group?

A

Part of the organic molecule that is largely responsible for the molecule’s chemical properties.
It can contain other elements

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5
Q

Name and explain the three classes of hydrocarbons.

A

Aliphatic- carbon atoms in a chain
Alicyclic- carbon atoms in a ring
Aromatic- carbon atoms in a benzene ring

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6
Q

What are the functional groups and prefixes/suffixes of:
a) alkenes
b) alcohols
c) haloalkanes
d) aldehydes
e) ketones
f) carboxylic acid
g) nitriles
h) amines
i) acyl chloride
j) acid anhydride
k) ester
l) amide

A

a) C=C ‘ene’
b) O-H ‘hydroxy/ol’
c) F/Cl/Br/I ‘fluoro/chloro/bromo/iodo’
d) O=C—H ‘al’
e) O=C (with c bonded to two other things) ‘oxo/one’
f) O=C—O—N ‘oic acid’
g) C-=C (triple bond) ‘nitrile’
h) H—N—H ‘amino/amine’
i) O=C—Cl ‘oyl chloride’
j) O=C—O—C=O
k) O=C—O
l) O=C—N—H2

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7
Q

What is a structural isomer?

A

Molecules with the same molecular formula but different structure

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8
Q

What is a stereoisomer?

A

Molecules with the same strict so formula but a different spatial arrangement of atoms.

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9
Q

Name the two ways covalent bonds can be broken. (2 marks)

A

Homolytic fission- each bonded atom takes one e-
Heterolytic fission- one atom takes both e-

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10
Q

What are curly arrows used to show?

A

Movement of a pair of electrons (when bonds are broken/made)

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11
Q

What are the 3 types of reaction?

A

Addition
Substitution
Elimination

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12
Q

What are 2 things you need to remember when drawing curly arrows?

A

(:) for electrons on ions
Delta + and delta - signs

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13
Q

What is a positional isomer?

A

Same chemical formula
Atom/group of atoms in a different position

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14
Q

What is an electrophile? (2 marks)

A

An atom or molecule that seeks an atom or molecule containing a pair of electrons available for bonding.
They accept a pair of electrons.

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15
Q

What is a nucleophile? (2 marks)

A

An electron rich species which can donate a pair of electrons.
They are attracted to positively charged species.

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16
Q

What is a radical?

A

An atom or group of atoms that have at least one unpaired electron.

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17
Q

What uses do these alkanes have?:
a) C-C4
b) C5-C9
c) C10-C16
d) C12-C20

A

a) gas
b) petrol
c) kerosene
d) diesel

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18
Q

What bonds are present in alkanes?
Explain what these bonds are.

A

Sigma bonds (covalent)
Forward overlap of two orbitals (can freely rotate)

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19
Q

What is the shape and bond angle of alkanes?

A

Tetrahedral shape
109.5 degrees

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20
Q

What is used to separate alkanes from crude oil?

Describe this process.

A

Fraction mall distillation.
Liquid + vapour pass into a tower that is cooler at the top, rise until they reach a tray which is cool enough to condense.

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21
Q

What is catalytic cracking?

A

Low temperature + pressure using zeolite

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22
Q

What is thermal cracking?

A

Beta alkanes at a high temperate and pressure to procure branches alkanes etc.

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23
Q

Why are alkanes not very reactive?

A

C—C and C—H bonds are strong
C—C bonds are non-polar
Electronegativity of carbon and hydrogen are so similar that the C—H bonds are considered non-polar

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24
Q

What does complete combustion of alkanes produce?

A

CO2 + H2O

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25
Q

What does incomplete combustion of alkanes produce?

A

CO + H2O

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26
Q

Explain how complete combustion of alkanes can contribute to environmental problems.

A

Produces CO2, this contributes to global warming.

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27
Q

Explain how incomplete combustion of alkanes can be dangerous.

A

Produces CO
A toxic, odourless, clear gas

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28
Q

What are the three stages for the mechanism for the reaction of a halogen with an alkanes, and what is it called?

Describe these three stages.

A

Initiation- covalent bond of diatomic halogen molecules break by homolytic fission

Propagation- radicals react with alkane twice (cycle)

Termination- two radicals collide, it stops the reaction

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29
Q

What is the trend in melting points in alkanes?

A

Increases as the chain length increase because there is a greater surface area of contact between molecules, therefore there are stronger induced dipole-dipole interactions.

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30
Q

What is the trend in volatility in alkanes?

A

Decrease as chain length increases because the longer the chain, the more opportunity for chain-chain interaction.

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31
Q

What is the trend in viscosity in alkanes?

A

Increases as chain length increases, because the intermolecular attractive fleeces increase, thus means nearby molecules get tangled more.

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32
Q

Describe and explain the effect of branching on the boiling points of alkanes.

A

The more branches the chain, the lower the boiling point.
This is because the molecules cannot pack together as tightly
So they have less surface area of contact
This the induced dipole-dipole forces between molecules get weaker
And the boiling points are lower

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33
Q

What are the conditions for the reaction of a halogen with an alkane?

A

Room temperature
UV light

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34
Q

What is an unsaturated hydrocarbon? (1 mark)

A

A hydrocarbon with at least one double or triple bond, or ring in it’s chain.

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35
Q

What is a pi bond? (3 marks)

A

The sideays overlap of two p-orbitals.
The pi-electron density is concentrated above and below the line joining the nuclei of the bonding atoms.

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36
Q

Can pi bonds rotate, why can/can’t they? (2 marks)

A

No, it locks the 2 carbon atoms in position.

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37
Q

What is the shape around each carbon atom in an Alkene, why? (3 marks)

A

Trigonal planar.
Three regions of electron density, repel equally (120 degrees).

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38
Q

What is the general formula for an Alkene? (1 mark)

A

Cn H2n

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39
Q

Why are alkenes more reactive than alkanes? (2 marks )

A

The double bond is an area of high electron density.
The pi bond is weaker.

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40
Q

What are dienes? (1 mark)

A

Hydrocarbons that contain two C=C bonds.

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41
Q

Compare and explain the boiling points of an alkene to it’s corresponding alkane. (4 marks)

A

The alkene had a boiling point that is a few number of degrees lower than the corresponding alkane.
Each alkene has 2 fewer electrons than the alkane.
So the induced dipole-dipole interactions are slightly weaker.
Less energy is needed to overcome interactions.
Therefore, lower boiling point.

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42
Q

What is sp^2 hybridisation? (2 marks)

A

The mixing of two electrons from a p orbital and one from an s orbital.
This creates three new hybrid orbitals at the same every level.

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43
Q

Why is a pi bond not as strong as a sigma bond? (1 mark)

A

Because they are sideways, rather than forward.

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44
Q

What must a compound have to have E/Z isomers? (2 marks)

A

C=C double bond
Different groups attached to each carbon atom in the double bond.

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45
Q

What is cis-trans isomerism? (3 marks)

A

Special case of E/Z isomerism
C=C bond
Same groups stretched to each carbon atom in the double bond.

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46
Q

Explain the Cahn-Ingold-Prelong rules. (2 marks)

A

The higher the atomic number, of the element directly attached to the C, the higher the priority.

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47
Q

Why do Z isomers have a higher boiling point than E isomers? (2 marks)

A

Z isomers are polar molecules
This means there are permanent dipole-dipole and induced dipole-dipole forces.
E isomers only have induced.

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48
Q

Why do E isomers have a higher melting point than Z isomers? (2 marks)

A

E isomers have a linear shape
So the pack together better than the Z isomers
Therefore have stronger intermolecular forces when solid.

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49
Q

What is the hydrogenation of an alkene? (2 marks)

A

Mixed with hydrogen
Passed over a nickel catalyst
Forms an alkane

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50
Q

What is the halogenating of an alkene? (2 marks)

A

Mixed with Cl or Br
At room temperature
Forms a haloalkane

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51
Q

Describe the reaction between an alkene and hydrogen halide. (2 marks)

A

Mixed with a hydrogen halide
At room temperature
Forms a haloalkane

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52
Q

What is the hydration of an alkene?

A

React with steam
Phosphoric acid catalyst
Forms an alcohol

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53
Q

What mechanism are the addition reactions of alkenes? (1 mark)

A

Electrophilic addition reactions

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54
Q

What is the chemical test for the presence of C=C bonds? (1 mark)

A

Aqueous bromine
Orange —> colourless

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55
Q

What do electrophilic addition reactions of unsymmetrical alkenes result in? (2 marks)

A

Carbocation intermediates —> possibility of two different products

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56
Q

What does Markovnikov’s rule state, explain? (4 marks)

A

The stability of carbocation intermediates depend on the number of alkyl groups attached.
Alkyl groups are electron donating groups.
Electron donating groups decrease the size of the positive charge on the carbon.
So the carbocation becomes more stable.

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57
Q

How are long saturated chains (addition polymers) formed from alkenes? (2 marks)

A

Polymerisation- repeated addition reactions

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58
Q

In what conditions is industrial polymerisation conducted in? (2 marks)

A

High pressure
High temperature

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59
Q

What is a repeat unit, and what mustn’t you forget about them? (3 marks)

A

The part that repeats in the polymer over and over again.
Always in square brackets
Put an n after the bracket (shows that there is a large number of repeats)

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60
Q

What mechanism is the polymerisation of alkenes? (1 mark)

A

Free radical addition

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61
Q

How can chemists modify the strength of intermolecular forces between polymer chains? (1 mark)

A

By including different substituent groups

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62
Q

What does including plasticisers do to a polymer, why? (3 marks)

A

Lower the melting point and tensile strength.
Increase flexibility.
The plasticisers are relatively small so they can penetrate between the polymer chains (reducing the strength of the intermolecular forces between them)

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63
Q

What does increasing the chain length of a polymer chain do to a polymer? (2 marks)

A

Increase melting point and tensile strength
Decrease flexibility

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64
Q

What does branching do to polymers? (2 marks)

A

Lower density, melting point, tensile strength and rigidity because it stops the molecules lining up regularly.

65
Q

Give two ways that waste polymers can be reused? (2 marks)

A

Melted and remoulded
Cracked and provide organic feeds

66
Q

What is an E isomer? (1 mark)

A

The priority groups are diagonal.

67
Q

What is a Z isomer? (1 mark)

A

The priority groups are on the same side.

68
Q

What is a cis isomer?

A

The same groups are on the same side (make a C shape)

69
Q

What is a trans isomer? (1 mark)

A

The same groups are on diagonal sides.

70
Q

What is an alcohol?
(1 mark)

A

A compound that contains hydroxyl (OH) group(s).

71
Q

Why are alcohols polar and what does this cause?
(4 marks)

A

Difference in electronegativity between delta negative O and delta positive H.
This means hydrogen bonds can be formed
and melting and boiling points are higher,
due to stronger intermolecular forces.

72
Q

Describe the trend in solubility in alcohols.
(3 marks)

A

As the hydrocarbon chain length of the alcohol increases, solubility decreases
because the influence of the hydroxyl group becomes relatively smaller,
decreasing the interactions with water molecules.

73
Q

What is a primary alcohol?
(1 mark)

A

When the carbon bonded to the hydroxyl group is attracted to one other carbon atom.

74
Q

What is a secondary alcohol?
(1 mark)

A

When the carbon bonded to the hydroxyl group is attracted to two other carbon atoms.

75
Q

What is a tertiary alcohol?
(1 mark)

A

When the carbon bonded to the hydroxyl group is attracted to three other carbon atoms.

76
Q

Describe the trend in boiling point of alcohols.
(3 marks)

A

Boiling point increases as the length of the carbon chain in the alcohol increases.
This is because the induced dipole-dipole interactions become stronger,
therefore more energy is required to overcome the intermolecular forces,
so the boiling point is higher.

77
Q

Why is propane-1,2,3-triol more soluble in water than propan-1-ol?
(4 marks)

A

Propane-1,2,3-triol has three hydroxyl groups.
Propan-1-ol has one hydroxyl group.
Propane-1,2,3-triol has more hydroxyl groups to form hydrogen bonds with water molecules.
The more hydrogen bonds formed between a molecule and water, the greater the solubility.

78
Q

What is the suffix for alcohols?
(1 mark)

A

-ol

79
Q

What shapes do alcohols form?
(2 marks)

A

Pyramid-like
Bent

80
Q

What should be included in a diagram showing hydrogen bonds?
(4 marks)

A

The HOH should be in a straight line
Partial charges
Line pair of electrons (on the oxygen)
Hydrogen bond should be labelled

81
Q

Do lone pairs or bonding pairs repel more?
(1 mark)

A

Lone pairs

82
Q

State and explain the HCH and COH angles in ethanol- might need paper.
(6 marks)

A

HCH:
4 areas of electron density
4 bonding pairs
Repel equally
109.5 degree bond angle

COH:
4 areas of electron density
2 bonding pairs, 2 line pairs of electrons
Lone pairs repel more
104.5 degree bond angle (109.5 - (2.5 x 2))

83
Q

Describe the combustion of alcohols. (4 marks)

A

Burn completely
In a plentiful supply of oxygen
To produce H2O and CO2
Exothermic reaction

84
Q

How are primary and secondary alcohols oxidised? (3 marks)

A

Using oxidising agents
Potassium dichromate
And dilute sulphuric acid

85
Q

If an alcohol os oxidised, what colour change is expected and why? (3 marks)

A

Orange to green
Redox reaction takes place
To produce water and chromium ions

86
Q

Describe how aldehydes are prepared. (3 marks)

A

Gently heating primary alcohol
With potassium dichromate and dilute sulphuric acid
The aldehyde is distilled out of the mixture as it forms

87
Q

Why is the aldehyde distilled out of the mixture as it is formed? (2 marks)

A

To prevent any further reaction with the oxidising agent
To ensure the aldehyde is formed rather than the carboxylic acid

88
Q

Describe how carboxylic acids are prepared. (2 marks)

A

Primary alcohol is heated strongly under reflux (with excess potassium dichromate and dilute sulphuric acid).

89
Q

When producing carboxylic acids, why is heating under reflux used? (1 mark)

A

It ensures that any aldehyde formed initially in the reaction also undergoes oxidation to produce the carboxylic acid.

90
Q

What is produced when a primary alcohol is partially oxidised? (1mark)

A

Aldehyde

91
Q

What is produced when a primary alcohol is fully oxidised? (1 mark)

A

Carboxylic acid

92
Q

What is produced when a secondary alcohol is oxidised? (1 mark)

A

Ketone

93
Q

How are ketones produced? (2 marks)

A

Heating secondary alcohols
Under reflux (with potassium dichromate and dilute sulphuric acid).

94
Q

How are tertiary alcohols oxidised? (1 mark)

A

THEY DO NOT UNDERGO OXIDATION REACTIONS

95
Q

What type of reaction is a dehydration reaction? (1 mark)

A

Elimination reaction

96
Q

What is removed during a dehydration reaction? (1 mark)

A

Water

97
Q

What is produced in a dehydration of alcohol reaction?

A

Alkene

98
Q

Describe how dehydration of alcohols is done?

A

Heated under reflux
In the presence of an acid catalyst

99
Q

What is produced from an alcohol and a hydrogen halide? (1 mark)

A

Haloalkane

100
Q

Describe the conditions of a substitution reaction of an alcohol.

A

Heated under reflux
With sulphuric acid and a sodium halide.

101
Q

What is a haloalkane? (1 mark)

A

Saturated hydrocarbons
Contain one or more halogen atoms

102
Q

What is a primary haloalkane? (1 mark)

A

The halogen is attached to a carbon atom which is bonded to one other carbon atom.

103
Q

What is a secondary haloalkane? (1 mark)

A

The halogen is attached to a carbon atom which is bonded to two other carbon atoms.

104
Q

What is a tertiary haloalkane (1 mark)

A

The halogen is attached to a carbon atom which is bonded to three other carbon atoms.

105
Q

Why is a C-halogen bond polar? (2 marks)

A

Halogens are more electronegative than carbon.
Therefore, the pair of electrons is closer to the halogen in the bond.
This makes it a polar bond.

106
Q

What is a nucleophile? (3 marks)

A

A species containing one or more lone pairs of electrons
Which can donate to an electron deficient atom
To form a covalent bond

107
Q

What is the trend in boiling point in haloalkanes, why? (3 marks)

A

Boiling point increases as halogen in it goes down group.
As the size of the halogen increases
The IDD forces of attraction increase
Increasing the boiling point.

108
Q

What is the trend in polarity of the haloalkanes? (1 mark)

A

Get less polar as go down group.

109
Q

What is nucleophilic substitution? (1 mark)

A

When one nucleophile replaces another in a molecule.

110
Q

What is formed when an OH- nucleophile reacts with a haloalkane? (1 mark)

A

Alcohol

111
Q

What is formed when a CN- nucleophile reacts with a haloalkane? (1 mark)

A

Nitrile

112
Q

What is formed when a 2NH3 reacts with a haloalkane? (1 mark)

A

Amine

113
Q

What conditions must there be to form an alcohol from a haloalkane and OH- nucleophile? (2 marks)

A

Aqueous NaOH
Reflux

114
Q

What conditions must there be to form a nitrile from a haloalkane and CN- nucleophile? (2 marks)

A

KCN in ethanol
Reflux

115
Q

What conditions must there be to form an amine from a haloalkane and NH3? (2 marks)

A

Concentrated NH3 in ethanol
Reflux

116
Q

Amines act as nucleophiles, what can this lead to? (1 mark)

A

Secondary and tertiary amines forming.

117
Q

To ensure only the primary amine is formed from the haloalkane, what is used? (1 mark)

A

Concentrated ammonia

118
Q

What is the trend in reactivity of the haloalkanes, why? (1 mark)

A

More reactive as go down the halogens, these bonds are weaker, easier to break, higher reactivity.

119
Q

What is organic synthesis? (1 mark)

A

Preparation of complex molecules from simple starting molecules.

120
Q

What is ozonolysis? (1 mark)

A

A technique to break open a C=C double bond.

121
Q

What is a target molecule? (1 mark)

A

The molecule that is attempting to be made.

122
Q

What functional group does an alkene have? (1 mark)

A

C=C double bond

123
Q

What functional group does an alcohol have? (1 mark)

A

OH

124
Q

What functional group does a ketone have? (1 mark)

A

C—C(=O)—C
A middle carbon with an oxygen attracted with a double bond

125
Q

What functional group does a nitrile have? (1 mark)

A

CN
(There is a triple bond between the C and N and the Cheadle is on the C)

126
Q

What functional group does an aldehyde have? (1 mark)

A

O=C—H

127
Q

What functional group does a haloalkane have? (1 mark)

A

A halogen
E.g. Cl, Br, I

128
Q

What functional group does a carboxylic acid have? (1 mark)

A

O=C—OH

129
Q

What functional group does an ester have? (1 mark)

A

O=C—OC

130
Q

What functional group does an amine have? (1 mark)

A

NH2

131
Q

What functional group does an acyl chloride have?

A

O=C—Cl

132
Q

What 3 things can make a haloalkane in 1 step, state the reactants and conditions? (6 marks)

A

Alkane: UV light + halogen
Alkene: hydrogen halogen, RTP
Alcohol: Sodium halogen + Sulphuric acid + RTP

133
Q

How can you make a dihaloalkane one step, state the reactants and conditions? (2 marks)

A

Alkene: UV light + halogen

134
Q

What 2 things can make an alcohol in 1 step, state the reactants and conditions? (4 marks)

A

Haloalkane: aqueous NaOH, reflux

Alkene: steam + concentrated sulphuric acid + 300 degrees + 60-70atm, catalytic hydration

135
Q

What can make an alkane in one step, state the reactants and conditions? (2 marks)

A

Alkene: halogen + nickel catalyst + 150 degrees, hydrogenation

136
Q

What is the only thing that can make an amine, in one step, state the reactants and conditions? (4 marks)

A

Haloalkane: concentrated ammonia +
aqueous ethanol, reflux

Haloalkane: excess amine in ethanol, reflux

137
Q

What is the only thing that a can make a nitrile in one step, state the reactants and conditions? (2 marks)

A

Haloalkane: KCN in ethanol, reflux

138
Q

What is the only way you can make an Alkene in one step, state the reactants and conditions? (2 marks)

A

Alcohol: concentrated sulphuric acid + 170 degrees

139
Q

What is the only thing you can use to make an aldehyde in one step, state the reactants and conditions? (2 marks)

A

Alcohol: potassium dichromate + excess sulphuric acid, oxidation, distillation

140
Q

What is the only way you can make a ketone in one step, state the reactants and conditions? (2 marks)

A

Alcohol: potassium dichromate + excess sulphuric acid, reflux, oxidation

141
Q

What is the only way you can make a carboxylic acid in one step, state the reactants and products? (2 marks)

A

Aldehyde: Potassium dichromate + excess sulphuric acid, reflux, oxidation

142
Q

What is reflux and why is it used? (2 marks)

A

Reflux is continuous boiling/evaporation and condensation.
It’s done to prevent loss of volatile liquids whilst heating.

143
Q

What is a molecular ion? (1 mark)

A

A molecule that is ionised in a mass spectrometer.

144
Q

What does a molecular ion fragment into? (2 marks)

A

Another positive fragment ion (which is detected)
And a neutral radical (which is not detected)

145
Q

Why does the fragmentation happen in the spectrometer? (1 mark)

A

The covalent bonds have been weakened by the loss of the electron from the molecule.

146
Q

In a mass spectra for an alkane, how can you tell the stability of the carbocation? (1 mark)

A

Higher peak on mass spectra

147
Q

What do carbonyls typically fragment into? (2 marks)

A

Acylium ion
Alkyl radical

148
Q

What affect does the C-13 isotope have on the mass spectra? (1 mark)

A

Creates an ‘M+1’ peak ( a tiny peak after the molecular ion peak)

149
Q

What happens when an organic compound is placed in a mass spectrometer? (1 mark)

A

It loses an electron and forms THE MOLECULAR ION (M+).

150
Q

How can the number of carbon atoms be found? (Hint: formular involving M+1 height) (2 marks)

A

(Height of M+1 peak/ height of M+ peak) x 100

151
Q

What does infrared radiation do to covalent bonds? (1 mark)

A

Make them bend or stretch more

152
Q

If covalent bonds posses energy, what does this mean they do? (2 marks)

A

Vibrate naturally about a central point

153
Q

What is a stretch? (2 marks)

A

Rhythmic movement along the line between atoms
The distance between the two atoms centres increases and decreases.

154
Q

What does a bend result in? (1 mark)

A

A change in bond angle.

155
Q

What does how much a bond stretches/bends rely on? (2 marks)

A

Mass of the atoms in the bond (heavier = vibrate slower).

Strength of the bond (stronger = vibrate faster)

156
Q

Any bond can only absorb radiation that…
(2 marks)

A

…has the same frequency as the natural frequency pf the bond.

157
Q

Describe and explain how global warming occurs.
(4 marks)

A

Some visible and IR radiation is re-emitted from the Earth’s surface,
in the form of longer-wavelength IR.
Greenhouse gases absorb these because it has the same frequency as their natural bonds.
Eventually, the vibrating bonds re-emit this energy as radiation,
that increases the temperature of the atmosphere close to the earth’s surface.

158
Q

IR spectroscopy can be used to identify the functional groups present in organic molecules. Describe how an IR spectroscope works.
(5 marks)

A
  1. Place sample inside
  2. Beam of IR radiation (200-4000cm-1) is passed through sample
  3. Molecule absorbs some of the IR frequencies
  4. The emerging beam is analysed to find out which frequencies were absorbed
  5. Usually connected to a computer which plots a graph of transmittance against wavenumber
159
Q

What is the typical sequence of techniques used for identification of an organic sample?
(3 marks)

A

Elemental analysis (% composition)
Mass spectrometry
IR spectroscopy

Chemistry Paper 2 (2 decks)

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