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Edexcel International A Level Chemistry

Topic 5
Alkenes

Alkenes are the gateway to organic reaction chemistry. This topic covers the structure of the carbon-carbon double bond, geometric isomerism, electrophilic addition mechanisms, polymerisation and polymer disposal – all examined directly in Unit 1 of the Edexcel International A Level Chemistry.

Exam Unit
Unit 1
WCH11/01 – IAS
Specification Points
5.1 – 5.8
8 points covered
Sub-topics
6 lessons
Revision notes available
Exam Board
Edexcel IAL
Pearson International

Revision Notes

Sigma + Pi
C=C
Bonding
1
Available

Alkene Bonding

Unsaturation, C=C double bonds, sigma and pi orbital overlap, and why alkenes react with electrophiles.

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Restricted rotation
E-Z
Isomers
2
Available

Geometric Isomerism

Restricted rotation around C=C, cis/trans naming, E-Z system and when it is required.

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Curly arrows
Electrophilic
Addition
3
Available

Electrophilic Addition Mechanism

Curly arrow notation, carbocation stability, and mechanism of bromine and HBr addition.

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Addition
Reactions
bromine water, HX, steam and oxidation
4
Available

Reactions of Alkenes

Hydrogenation, halogenation, addition of HX, hydration, oxidation and the bromine water test.

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Monomer to polymer
Repeat
Units
5
Available

Polymerisation Reactions

Addition polymerisation, drawing repeat units, and converting between monomers and polymers.

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Polymer
Disposal
biodegradable materials and toxic gases
6
Available

Polymer Waste

Biodegradable polymers, polymer disposal, incineration and removing toxic waste gases.

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Specification Coverage

Topic 5 Alkenes – Edexcel International A Level Chemistry

The following specification points outline the knowledge and skills students are expected to demonstrate for Topic 5.

5.1
know the general formula of alkenes and understand that alkenes and cycloalkenes are hydrocarbons which are unsaturated (have a carbon-carbon double bond which consists of a σ bond and a π bond)
5.2
be able to explain geometric isomerism in terms of restricted rotation around a C=C double bond and the nature of the substituents on the carbon atoms
5.3
understand the E-Z naming system for geometric isomers and why it is necessary to use this when the cis- and trans- naming system breaks down
5.4
be able to describe the reactions of alkenes, limited to:
i
the addition of hydrogen, using a nickel catalyst, to form an alkane
ii
the addition of halogens to produce a di-substituted halogenoalkane
iii
the addition of hydrogen halides to produce mono-substituted halogenoalkanes
iv
the addition of steam, in the presence of an acid catalyst, to produce alcohols
v
oxidation of the double bond by acidified potassium manganate(VII) to produce a diol
5.5
know the qualitative test for a C=C double bond using bromine or bromine water
5.6
be able to describe the mechanism (including diagrams), giving evidence where possible, of:
i
the electrophilic addition of bromine and hydrogen bromide to ethene
ii
the electrophilic addition of hydrogen bromide to propene
Use of the curly arrow notation is expected. The curly arrows should start from either a bond or from a lone pair of electrons. Knowledge of primary, secondary and tertiary carbocation stability is expected.
5.7
be able to describe the addition polymerisation of alkenes and draw the repeat unit given the monomer, and vice versa
5.8
understand how chemists limit the problems caused by polymer disposal by:
i
developing biodegradable polymers
ii
removing toxic waste gases produced by the incineration of polymers
Specification Coverage

Topic 5 Alkenes – Edexcel International A Level Chemistry

The following specification points outline the knowledge and skills students are expected to demonstrate for Topic 5.

5.1
know the general formula of alkenes and understand that alkenes and cycloalkenes are hydrocarbons which are unsaturated (have a carbon-carbon double bond which consists of a σ bond and a π bond)
5.2
be able to explain geometric isomerism in terms of restricted rotation around a C=C double bond and the nature of the substituents on the carbon atoms
5.3
understand the E-Z naming system for geometric isomers and why it is necessary to use this when the cis- and trans- naming system breaks down
5.4
be able to describe the reactions of alkenes, limited to:
i
the addition of hydrogen, using a nickel catalyst, to form an alkane
ii
the addition of halogens to produce a di-substituted halogenoalkane
iii
the addition of hydrogen halides to produce mono-substituted halogenoalkanes
iv
the addition of steam, in the presence of an acid catalyst, to produce alcohols
v
oxidation of the double bond by acidified potassium manganate(VII) to produce a diol
5.5
know the qualitative test for a C=C double bond using bromine or bromine water
5.6
be able to describe the mechanism (including diagrams), giving evidence where possible, of:
i
the electrophilic addition of bromine and hydrogen bromide to ethene
ii
the electrophilic addition of hydrogen bromide to propene
Use of the curly arrow notation is expected. Knowledge of primary, secondary and tertiary carbocation stability is expected.
5.7
be able to describe the addition polymerisation of alkenes and draw the repeat unit given the monomer, and vice versa
5.8
understand how chemists limit the problems caused by polymer disposal by:
i
developing biodegradable polymers
ii
removing toxic waste gases produced by the incineration of polymers