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Chemistry A - Level > Topic 6A,B,C - Alkanes and Alkenes (Organic Chemistry) > Flashcards

Topic 6A,B,C - Alkanes and Alkenes (Organic Chemistry) Flashcards

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1
Q

What is a Homologous series?

A

A series of compounds containing the same functional group so have same general formula and chemical properties

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2
Q

What is a Functional Group?

A

A single atom or group of atoms that gives a compound its chemical properties

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3
Q

Definition of Molecular formula

A

The formula which shows the actual number of each type of atom

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4
Q

Definition of a empirical formula

A

Show the simplest whole number ratio of atoms of each element in the compound

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5
Q

Definition of Structural formula

A

Shows how atoms are grouped together in a molecule

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6
Q

Definition of Displayed formula

A

Shows all the atoms and all the bonds in a molecule

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7
Q

Definition of Skeletal formula

A

Shows a simplified structural formula only show carbon -carbon bonds (as lines) and functional groups of present

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8
Q

What are 3 properties of a homologous series

A
  1. They show a gradual change in physical properties e.g boiling point
  2. Each member differs by CH2 (the same difference) from the last
  3. They have the same chemical properties
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9
Q

What are the general rules for naming carbon chains?

A
  1. Count the longest carbon chain and name appropriately, find any branched chains and figure out the carbon they are coming off and the functional group that they are e.g 3,5 - dimethylheptane meaning that the longest carbon chain is 7 and there are 2 methyl groups coming off the 3rd and 5th carbon
  2. You have to make sure that the numbers are the smallest possible
  3. When naming with multiple functional groups the order of them is alphabetical
  4. Words are separated by numbers with dashes and numbers are separated by commas
  5. When writing the structural formula of molecules that have functional groups e.g methyl coming off of them you need to put brackets around it e.g CH3CH(CH3)CH3
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10
Q

Definition of an Isomer/ structural isomer

A

Molecules with the same molecular formula but a different structural formula

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11
Q

What are the 2 types of isomers?

A
  • structural isomers
  • stereoisomers
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12
Q

What are the 3 types of structural isomers?

A
  • Chain isomers
  • position isomers
  • Functional group isomers
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13
Q

What is the definition of a chain isomer?

A

Compounds with the same molecular formula but different shaped/ structured chains e.g straight chain or branched e.g pent-1-ene and 3-methylbut-1-ene

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14
Q

What is the definition of a position isomer?

A

Compounds with the same molecular formula but different structures due to different positions of the functional group on the molecules e.g pent-1-ene and pent-2-ene

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15
Q

What is the definition of a functional group isomer?

A

Compounds with the same molecular formula but with the atoms arranged to give different functional groups e.g Alkenes and Cyclo Alkanes have the same molecular formula but different functional groups

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16
Q

What is the definition of a stereoisomer?

A

Molecules with the same molecular and structural formula but with a different arrangement of atoms in space e.g cis/trans isomers and E/Z isomers

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17
Q

What are the 5 types of reactions?

A

Addition, Polymerisation, Elimination, Substitution, Hydrolysis.

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18
Q

When do addition reactions occur?

A

When molecules contain a double bond e.g In Alkenes, they are said to be unsaturated and the carbon-carbon double bond can break and gain another molecule in an addition reaction.

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19
Q

When do polymerisation reactions occur and give an example?

A

Addition polymerisation occurs when small molecules (monomers) with double bonds e.g Alkenes, add to each other and join up in long chains to form polymers. The reaction
needs a suitable catalyst and temperature. An example; n(C2H4) -> -(C2H4)-n

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20
Q

When do elimination reactions occur and give an example?

A

An elimination reaction is basically the opposite of an addition reaction, it splits off a simple molecule e.g water or hydrogen chloride, from a larger molecule leaving a double bond e.g C2H5Cl -> C2H4 + HCl (in the presence of NaOH, ethanol and heat)

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21
Q

When do substitution reactions occur and give an example?

A

Substitution reactions occur when an atom or group of atoms is replaced by another atom or group of atoms e.g alkanes + halogens (in the presence of UV light) -> halogenoalkanes + Hydrogen halides

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22
Q

When do hydrolysis reactions occur and give an example?

A

Hydrolysis is used to describe any reaction in which water is used to split apart a molecule (don’t need to know the process in detail). To recognise this reaction you would see water as a reactant and the reaction is often catalysed by an alkali or acid. Hydrolysis reactions are often substitution reactions in which the chemical attack is by nucleophiles such as water molecules or hydroxide ions.

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23
Q

What are nucleophiles?

A

Nucleophiles are molecules or ions that have a lone pair of electrons that is able to form a new covalent bond. For example; Oxygen in hydrogen oxide, Carbon in carbon nitride, Oxygen in water, Nitrogen in Ammonia

  • They are electron pair donors
  • They attack ions/molecules with a partially positive charge
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24
Q

What are electrophiles?

A

An electrophile is a species which can accept a pair of electrons from an electron rich sire in another molecule to form a new covalent bond. Electrophiles are often positively charged e.g H+

  • They are ‘electron loving’ reagents
  • Electrophiles form a new bond by accepting a pair of electrons from the molecule or ion attached in the reaction
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25
Q

What is a polymer?

A

Polymers are large chains formed from huge numbers of small molecules (repeat units) called monomers

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26
Q

What type of addition do alkenes undergo?

A

Electrophilic addition - The electrophiles (the positive ions with a vacant orbital) attack the negatively charged region of the C=C bond

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27
Q

What is the definition of addition polymerisation?

A

The joining together of small molecules that contain a carbon-carbon double bond to form a long chain

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28
Q

What are two safety hazards when cracking and what is the solution to them?

A
  • One hazard is that the gas you are producing and paraffin is flammable so therefore you have to make sure the gas is being collected over water
  • One hazard is that the glassware can get very hot as it is being heated so before you move touch it ensure it has cooled down
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29
Q

What is the shape of a saturated hydrocarbon?

A

Tetrahedral with a bond angle of 109.5°

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30
Q

What is homolytic fission?

A

This is when each atom of a molecule gets one electron from the covalent bond, the electrons are shared equally.

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31
Q

What are cycloalkanes?

A

These molecules contain a ring of carbon atoms and have the general formula CnH2n (same as alkenes)

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32
Q

How would you draw 2,2 -dimethylheptane

A

7carbon atoms making up the main chain and then on the second carbon atom their would be two methyl groups coming off it.

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33
Q

What type of bonds do alkanes contain?

A

Single covalent bonds known as sigma bonds

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34
Q

What is the bond axis?

A

The bond axis is the invisible line between the nuclei of the atoms being bonded together

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35
Q

When will sigma bonds form?

A

When their is head on overlap of orbitals along the bond axis

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36
Q

What are the 3 ways sigma bonds can form?

A
  • The overlap of 2 sigma bonds
  • The overlap of a sigma bond and a head on pi bond
  • The head on overlap of 2 pi bonds
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37
Q

Are alkanes reactive? Why?

A

No, as the C-C and C-H bonds have high bond energy values which require a lot of energy to overcome

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38
Q

Are alkanes likely to be polar molecules? Why?

A

No, as there are no polar bonds between the carbon and hydrogen as the difference in electronegativities is negligible

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39
Q

What are 2 qualities about the carbon-carbon bond in alkanes?

A
  • It is symmetrical
  • There is free rotation about the single bond
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40
Q

Alkane + Halogen →…

A

NO REACTION

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41
Q

What is the reaction of a Halogen with an organic compound used to test for?

A

Whether the compound is an alkene or alkane

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42
Q

What is the colour change of Bromine Water if an alkene functional group is present?

A

Orange→ colourless

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43
Q

What are the conditions need in order for the substitution reaction of; Alkane + Halogen → Halogenoalkane + Hydrogen Halide

A
  • UV radiation (sunlight) or above 300°C
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44
Q

What is the definition of a substitution reaction?

A

Where an atom or group of atoms is replaced with a different atom or group of atoms, 2 reactants → 2 products

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45
Q

What is Halogenation?

A

Where an alkane and a halogen (chlorine or bromine) react in the presence of UV radiation (sunlight)

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46
Q

What type of reaction is halogenation?

A

Free radical substitution (also a photochemical reaction)

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47
Q

What are the 3 stages of a Halogenation reaction?

A

Initiation
Propagation
Termination

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48
Q

What does a half arrow indicate when drawing a mechanism?

A

Movement of a single electron

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49
Q

What does a full arrow indicate when drawing a mechanism?

A

Movement of a pair of electrons

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50
Q

What happens in the Initiation step of Halogenation?

A

The UV light breaks down a chlorine/bromine molecule into uncharged halogen atoms, each with an unpaired electron show as a * (*=dot)

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51
Q

What is heterolytic fission?

A

This means that the electrons are split unequally between the atoms in the molecule and one atom gains a lone pair of electrons.

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52
Q

What are Free radicals?

A

Atoms that are uncharged and have 1 unpaired electron

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53
Q

Write the mechanism for the initiation step of the reaction; CH4 + Cl2 → CH3Cl + HCl

(You don’t need to know the mechanism)

A

Cl-Cl → Cl+Cl
Half arrows would be drawn from the bond to each Chlorine atom to show the movement of electrons

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54
Q

How many parts are there to the Propagation step of Halogenation?

A

2

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55
Q

For a reaction to occur what must happen?

A

Particles must collide with each other

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56
Q

Write the equation for the first part of the Propagation step of the reaction; CH4 + Cl2 → CH3Cl + HCl

A

CH4 + Cl* → C*H3 + HCl

From the C-H bond, 1 electron goes to the Carbon atom and 1 to the Hydrogen atom. The electron from the Chlorine free radical joins with the Hydrogen free radical.
Remember to draw the radical on the carbon atom

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57
Q

Write the equation for the second part of the Propagation step of the reaction; CH4 + Cl2 → CH3Cl + HCl

A

CH3 + Cl2 → CH3Cl + Cl

A different Cl2 molecule that has already been split in the first step donates one of its electrons to form a covalent bond with the carbon atom and its electron

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58
Q

What does the Propagation step continually do in the reaction; CH4 + Cl2 → CH3Cl + HCl?

A

Produce methyl and chlorine free radicals in a chain reaction

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59
Q

When does the chain reaction of a Halogenation reaction stop?

A

When all the free radicals eventually collide with each other

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60
Q

What are all the possible reactions for the final Termination step of the reaction; CH4 + Cl2 → CH3Cl + HCl?

A

Cl* + Cl* → Cl2

CH3 + Cl → CH3Cl

CH3 + CH3 → CH3CH3

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61
Q

Why does the reaction; CH4 + Cl2 → CH3Cl + HCl, have a low yield of product?

A

This is because the Cl* is so reactive and so therefore their are further free radical reactions of the radical with the desired product, which produces unwanted products.

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62
Q

Explain how crude oil is split into fractions via fractional distillation?

A

The crude oil is vaporised into a gas and enters the fractionating column which has a temperature gradient, hottest at the bottom and cooling as you go up. The long chain hydrocarbons with the highest boiling points will condense first, ant the bottom, and exit the column. The shorter chain hydrocarbons with the lowest boiling points will condense at the top.

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63
Q

What are the crude oil fractions from shortest chain length to longest?

A

Refinery Gas
Gasoline/Petrol
Naphtha
Kerosine
Diesel Oil
Lubricating oil
Fuel oil
Bitumen

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64
Q

Why do different alkanes have different boiling points?

A

Longer chain alkanes contain more electrons, therefore stronger London Forces which require more energy to overcome.

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65
Q

What are the two ways fractions are processed into more useful alkanes and alkenes?

A

Cracking
Reforming

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66
Q

What is the definition of reforming?

A

Turning straight chained alkanes into branched or cyclic alkanes, which are more efficient fuels as they combust easier

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67
Q

Why are cyclic or branched alkanes more useful?

A

They combust more easily so are more efficient fuels

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68
Q

What is the definition of cracking?

A

The breaking down of saturated hydrocarbon molecules into smaller hydrocarbon molecules by heat

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69
Q

Why is cracking an important process?

A

The process breaks down longer chain alkanes into shorter chain alkanes and alkenes that are in higher demand and are much more useful for the production of polymers for plastics

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70
Q

What are the two different conditions that are needed for cracking?

A

High temperatures

An aluminium oxide catalyst with low temperatures (catalytic cracking)

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71
Q

Describe the set up for catalytic cracking

A

On the right;
- a water bath
- downturned test tube that collects the gaseous product
- a Bunsen valve around the neck of the small tube that connects the test tube in the water bath and the test tube where the reaction is taking place

On the left;
- a sideways test tube
- aluminium oxide granules in the centre of the test tube
- a bung on the test tube
- Heat applied to the aluminium oxide
- ceramic fibre soaked in paraffin at the bottom of the test tube

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72
Q

What do fuels do when burnt?

A

Release heat energy

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73
Q

When does complete combustion occur?

A

In an excess/ plentiful supply of oxygen

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74
Q

What are the products of complete combustion?

A

Carbon dioxide + Water

75
Q

When does incomplete combustion occur?

A

When there is a limited supply of oxygen

76
Q

What are the products of incomplete combustion?

A

Water + CO/C (soot)

77
Q

Why is carbon monoxide dangerous?

A

Carbon monoxide binds irreversibly to haemoglobin in the blood, meaning that there is less supply of oxygen to organs

78
Q

What is the impact of soot in the environment?

A

Soot particulates can travel up into the atmosphere and reflect the suns light, contributing to global dimming

79
Q

How are oxides of sulphur formed? What do they cause?

A

Some hydrocarbon fractions contain sulphur impurities. When these fractions are burnt the reaction S + O2 → SO2 takes place. The sulphur dioxide will rise up into the atmosphere and dissolve in the atmospheric water to form acid rain.

80
Q

How are oxides of nitrogen formed? What do they cause?

A

Inside car engines the temperature is very high. This means nitrogen in the air and oxygen are able to react;
N2 + O2 → 2NO
N2 + 2O2 → 2NO2
NO is toxic and forms smog
NO2 is toxic and can also rise up into the clouds and dissolve in atmospheric water to form acid rain

81
Q

What do catalytic converters do?

A

They remove; CO, nitrogen oxides and unturned hydrocarbons from the exhaust gases of cars, turning them into less harmful; CO2, N2 gas and water

82
Q

An example equation of a catalytic converter is; 2CO + 2NO → …

A

2CO2 + N2

83
Q

What is the structure of catalytic converters? Why?

A

They have a honeycomb structure which gives them a large surface area

84
Q

What are the catalyst metals used in catalytic converters?

A

Platinum, palladium, rhodium

85
Q

What are 2 examples of renewable, plant based fuels?

A

Alcohols and Biodiesel

86
Q

What is a natural way that ethanol can be produced?

A

Via the fermentation of glucose from plants

87
Q

Write a symbol equation showing the fermentation of glucose

A

C6H12O2 → 2C2H6O + CO2

88
Q

What is used to catalyse the fermentation of glucose?

A
  • yeast
  • anaerobic conditions
89
Q

How is biodiesel produced?

A

Reacting vegetable oils with a mixture of alkali and methanol

90
Q

Why is the use of biofuels described as being carbon neutral?

A

When the biofuels are burnt, the CO2 that was taken up during photosynthesis when the plants were growing is released back into the air

91
Q

What are 3 advantages of using biofuels?

A
  • Renewable and sustainable energy source
  • More carbon neutral
  • Using Biofuels means using up less fossil fuels so there are more for making other organic compounds
92
Q

What are 3 disadvantages of using biofuels?

A
  • Production of them can be inefficient
  • They use chemical pesticides and fertilisers in order to grow the plants
  • less space from planting food crops
  • shortage of fertile soil
93
Q

What property allows crude oil to be separated by fractional distillation?

A

It is a mixture of hydrocarbons with different boiling points

94
Q

Why does the process of cracking require high temperatures?

A

In order to break the bonds between carbons

95
Q

Why are alkenes more reactive than alkanes?

A

In alkenes the pi bond will break easily as the pi electrons lie exposed above and below the rest of the molecule, so they are less controlled by the carbon nuclei, therefore they are relatively open to attack by other things. Alkanes only contain this sigma bond which is less likely to be attacked and broken.

96
Q

Why are alkenes referred to as unsaturated hydrocarbons?

A

As they contain a carbon-carbon double bond

97
Q

When naming the organic compound, what must the longest carbon chain contain in alkenes?

A

The C=C bond

98
Q

How is the chain numbered in alkenes?

A

To show the position of the double bond, giving it the lowest number possible

99
Q

Draw the display formula of but-2-ene

A
  • Double bond between the 2nd and 3rd carbon
100
Q

Draw the display formula of pent - 1,3 - diene

A
  • Double bonds between the 1st - 2nd, 3rd - 4th carbon
101
Q

Draw the display formula of cyclohexa - 1,3 - diene

A

The display formula of cyclohexane but with 2 double bonds that are one space apart (you label the carbons the numbers that you want as it doesn’t make a difference)

102
Q

What does the shape of a molecular orbital show?

A

The regions of space within the molecule where there is a high probability of finding a particular pair of electrons

103
Q

What does atomic orbitals overlapping result in?

A

Bonding between atoms

104
Q

When do molecular orbitals form?

A

When atomic orbitals overlap

105
Q

What is a sigma bond?

A

A single covalent bond formed by a pair of electrons in an orbital in a molecule

106
Q

Where is the electron density found in a sigma bond?

A

Between the 2 nuclei

107
Q

Where are pi bonds found?

A

In double and triple bonds

108
Q

How is a pi bond formed?

A

The sideways overlap of 2 p orbitals

109
Q

Where is the electron density found in a pi bond?

A

The electron density in a pi bond is concentrated in 2 regions, one above and one below the plane of the molecule

110
Q

Why is rotation around a pi bond restricted?

A

As if there was any rotation the p-orbitals would no longer overlap sideways

111
Q

How do you draw electron density in a carbon double bond?

A
  • A circle between the nuclei due to the sigma bond
  • 2 circles, above and below the sigma electron density, due to the pi bond
112
Q

What is the shape and bond angle of alkene molecules around the C=C bond?

A
  • Planar shape
  • 120° between the Hydrogen and Carbon atom
113
Q

When an alkene reacts which bond breaks and why?

A

The pi bond as it has a lower bond energy than a sigma bond so it is energetically more favourable to have 2 molecules with sigma single bonds.

114
Q

Draw and name the structural isomers with the molecular formula C4H8

A

but-1-ene, but-2-ene, 2-methylpropene

115
Q

What two factors are required for geometric isomers to form/be possible?

A
  • Presence of a C=C bond
  • Each Carbon in the double bond must have a different atom or group bonded to it
116
Q

Why does a geometric isomer require a C=C bond?

A

In a C=C bond the carbon atoms cannot rotate about the bond

117
Q

When does a geometric isomer have the prefix cis?

A

When the same group, on the different carbon atoms, are on the same side

118
Q

When does a geometric isomer have the prefix trans?

A

When the same group, on the different carbon atoms, are on different sides

119
Q

Draw the cis and trans isomers of C4H8

A

1 - Has 2 hydrogen groups on the same side
2 -Has 2 hydrogen groups on opposite sides

120
Q

When can you not have a geometric isomer?

A

When you have 2 of the same functional groups/ groups of atoms coming off the same carbon

121
Q

Why is it not always possible to use cis/trans naming when naming geometric isomers?

A

As cis/trans requires one group on the different carbon atoms to be the same, if the groups are all different you cannot use this naming method

122
Q

When do we use E/Z naming?

A

When no 2 groups are common/the same around a double bond

123
Q

What is the priority group?

A

The atom, or group of atoms, which the highest atomic number on each of the carbons. When these are on the same side it is a Z stereoisomer and when these are on opposite sides it’s is an E isomer

124
Q

What do E and Z mean/stand for?

A

E - entgegen, opposite
Z - zusammen, the same

125
Q

Which bond is weaker, pi or sigma?

A

Pi bond

126
Q

What is the reagent in the bromination of Ethene?

A

Bromine (In general the halogen)

127
Q

What are the conditions required for the bromination of Ethene?

A

Room Temperature

128
Q

What type of reaction is the bromination of ethene?

A

Electrophilic addition, where the electrophile Br (partially +) is attracted to the negatively charged region of the C=C bond

129
Q

How does the Br2 molecule that is non-polar gain a partially positive and negative charge in the bromination of Ethene?

A

As the Br2 molecule approaches the high electron density pi bond, the electrons within the Br2 molecule are repelled from one end giving that end a delta + charge (an induced dipole)

130
Q

What type of bond breaking takes place In the bromination of Ethene? In what bond?

A

Heterolytic Fission occurs in the Br-Br bond

131
Q

What happens when the Br2 bond breaks heterolytically?

A
  • The Br atom gaining the electrons gains a lone pair of electrons and an overall negative charge
  • The Br atom that has a partially positive charge and is being attracted to the pi bond, forms a new C-Br bond
132
Q

Write the equation for the reaction between ethene and bromine

A

C2H4 + Br2 → CH2BrCH2Br

133
Q

What is the C2H4Br molecule?

A

A carbocation, as there is a positive charge on the carbon

134
Q

In the bromination of Ethene what does the carbocation attract to form?

A

The carbocation attracts the Br- ion to form another C-Br bond and the molecule 1,2-dibromoethane

135
Q

Draw out the reaction mechanism for the bromination of Ethene?

A

1st Step
- Br2 has a dipole, partially positive closer to the double bond and the other side negative
- An arrow is drawn from the C=C bond to the Br (delta +) atom
- An arrow is drawn from the Br-Br bond to the Br (delta -)

2nd Step
- The Br- ion has a lone pair of electrons
- The Carbocation has a positive charge on a carbon that was in the double bond
- An arrow is drawn from the lone pair of electrons to the carbon with a positive charge

This forms a dihaloalkane

136
Q

Write the equation for the reaction of Alkenes (ethene) and Bromine Water

A

C2H4 + H2O + Br2 → CH2BrCH2OH + HBr

137
Q

What does H2O dissociate into?

A

OH- and H+ (this reaction is reversible and constantly happening)

138
Q

What is the major product of the reaction of Ethene with bromine water? Why?

A

2-bromoethanol. This is because OH- ions take part in the reaction and ,since they are a stronger Nucleophile than Br- ions, they bond with the carbon atom with a + charge

139
Q

Draw out the reaction of Ethene with Bromine water

A

1st Step
- Br2 has a dipole, partially positive closer to the double bond and the other side negative
- An arrow is drawn from the C=C bond to the Br (delta +) atom
- An arrow is drawn from the Br-Br bond to the Br (delta -)

2nd Step
- There is a Br- ion, however this does not take part in the reaction
- There is an OH- ion with a lone pair of electrons, acting as the nucleophile
- The carbocation has a positive charge on one of the carbons that was involved in the carbon-carbon double bond
- An arrow is drawn from the lone pair of electrons on the OH- ion to the Carbon+ ion

This forms a haloalcohol

140
Q

Why do alkenes undergo electrophilic reactions?

A

As alkenes contain a double bond, which forms a region of high electron density, that is negatively charged. This strongly attracts electrophiles, species that want to gain electrons.

141
Q

Write the equation for the reaction of an alkene (ethene) with a hydrogen Halide (hydrogen bromide)

A

C2H4 + HBr → CH3CH2Br

142
Q

What is the reagent and the conditions in the reaction of C2H4 and HBr?

A

Reagant - HCl or HBr gas
Conditions- Room Temperature

143
Q

Why does the H atom act as the electrophile in H-Br?

A

The molecule is polarised as Br has a higher electronegativity. This gives H a partially positive charge which therefore attracts the electrons in the C=C bond

144
Q

Draw out the mechanism of the reaction of Ethene with hydrogen bromide

A

1st Step
- The H-Br molecule has a partially positive charge on the H atom and partially negative charge on the Br atom (the molecule is already polarised)
- An arrow is drawn from the C=C bond to the H atom
- An arrow is drawn from the H-Br bond to the Br atom

2nd Step
- The Br- ion has a lone pair of electrons
- The Carbocation has a positive charge on a carbon that was in the double bond
- An arrow is drawn from the lone pair of electrons to the carbon with a positive charge

This forms a Halogenoalkane

145
Q

Which reaction with an alkene produces a major and minor product?

A

Alkene + Hydrogen Halide

146
Q

Why does propene produce a major and minor product but not ethene or but-2-ene?

A

Ethene and but-2-ene are symmetrical molecules so you will produce the same product. Propene is not symmetrical so therefore 2 different products can be formed from its reaction

147
Q

Draw the 2 possible products of the reaction of propene + HBr

A
  • 2-bromopropane (bromine on the second C atom)
  • 1-bromopropane (bromine on the first C atom)
148
Q

What is the major product of the reaction of propene + HBr?Why?

A

2-bromopropane is the major product. This is because it goes via a secondary carbocation which is more stable that a primary carbocation, which 1-bromopropane is produced by, as it has electrons donated by 2 alkyl groups rather than just one.

149
Q

What is the difference between a primary and secondary carbocation?

A

The positively charged carbon is surrounded by 2 alkyl groups in a secondary carbocation in comparison to only 1 alkyl group in a primary carbocation

150
Q

What is the definition of the inductive effect?

A

The tendency of atoms or groups of atoms to push electrons (or pull electrons towards a carbon atom)

151
Q

Why is a major product more likely to form via a secondary carbocation intermediate?

A

A secondary carbocation is more stable, due to more alkyl groups stabilising the positive charge with electrons, therefore the major product is more likely to form

152
Q

Alkyl groups are electron…

A

Donating

153
Q

Explain, by referring to the mechanism, why the major product is formed in the reaction of C3H6 + HBr → CH3CHBrCH3

A

2-bromobutane is the major product as it is formed via the secondary carbocation. This means it is more stable than the primary carbocation which the 1-bromobutane forms via, as the bromine is bonded to a carbon which is bonded to 2 alkyl groups, not just one

154
Q

When do alkenes react with potassium manganate?

A

The cold

155
Q

Write the equation for the reaction of Ethene with the oxidising agent potassium manganate (VII) solution

A

C2H4 + H2O +[O] → CH2OHCH2OH (a diol)

156
Q

What are the reagents and conditions for the reaction of Alkene with Potassium Manganate?

A

Conditions - Cold
Reagant - KMnO4 (potassium manganate VII) acidified with sulfuric acid

157
Q

What is the test for the alkene functional group?

A

Add KMnO4 (Potassium Manganate VII) solution

158
Q

What is the colour change for the test for alkenes?

A

Purple → colourless
(In alkali conditions a brown precipitate may form )

159
Q

What are the conditions required for ethene to react with H2 gas?

A
  • Nickel catalyst
  • High Pressure (20atm)
160
Q

Write the equation for the reaction of Ethene with Hydrogen gas

A

CH2CH2 + H2 → (Ni) CH3CH3

161
Q

What is the reaction of Ethene + Hydrogen gas used to prepare?

A
  • Alkanes
  • It saturates the double bonds in natural oils to make them into solids, for example manufacturing margarine from vegetable oils
162
Q

What are the conditions need for alkenes to react with steam?

A
  • Phosphoric acid catalyst
  • 60-70 atm
  • 300°C
163
Q

What functional group is produced from the reaction of alkenes with steam?

A

Alcohols, OH

164
Q

What is the reagent in the reaction of alkene and steam?

A

Steam

165
Q

Write a balanced polymer equation for the monomer but-1-ene (you can also be asked to draw the monomer from the polymer given)

A

n (display formula of but-1-ene) → [CH2CH(CH3)] polybut-1-ene

Note: the polymer display formula has a singe C-C bond not a double and has arms that extend through the brackets

166
Q

What are the conditions required for polymerisation reactions?

A
  • High pressure
  • Suitable catalyst
167
Q

What are the 4 main methods of disposal of alkenes/organic compounds?

A
  • Recycling
  • Incineration
  • Landfill
  • Feedstock for cracking
168
Q

What are some pro’s of recycling?

A
  • Reduces the waste to landfills
169
Q

What are some cons of recycling?

A
  • Slow process
  • Costly
  • Difficult
170
Q

What are some pro’s of incineration?

A
  • Produces energy that can by used to heat
171
Q

What are some cons of incineration?

A
  • Increases greenhouse gas emissions and therefore the enhanced greenhouse effect
  • Could release toxic gases
172
Q

What are some pro’s of a landfill?

A
  • Cheap
  • Easy
    -Quick
173
Q

What are some cons of a landfill?

A
  • Takes up space
  • Visual pollution
174
Q

What are some pro’s of Feedstock for cracking?

A
  • Prevents excess use of crude oil
175
Q

What are some cons of Feedstock for cracking?

A
  • decomposition produces methane as a greenhouse gas
176
Q

What is the definition of biodegradable?

A

The ability of a material to decompose by bacteria or other living organisms

177
Q

What are 2 examples of a biodegradable polymer?

A
  • Cellulose
  • Polypeptides
178
Q

What are 2 major uses of the polymer polythene?

A
  • Plastic; bags, bottles and beakers
  • Insulation for cables
179
Q

What are 2 major uses of the polymer Polypropene?

A
  • Fibre for ropes and carpet
  • Toys
180
Q

What are 2 major uses of the polymer PVC?

A
  • Guttering and window frames
  • Waterproof; clothing, flooring and clingfilm
181
Q

What are 2 properties of the polymer polythene?

A
  • Light
  • Flexible
  • Easily molded
  • Transparent
182
Q

What are 2 properties of the polymer Polypropene?

A
  • Tough
  • Easily molded and coloured
183
Q

What are 2 properties of the polymer PVC?

A
  • Tough
  • Very resistant to water, acids and alkalis

Chemistry A - Level (26 decks)

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