Reactions of Alkenes
Alkenes react because the carbon-carbon double bond contains an electron-rich pi bond. These pages separate the key addition reactions and chemical tests so students can revise reagents, conditions, products and observations clearly.
Revision Notes
5 revision notes, in the order the specification teaches them.
Halogens
Revise the addition reactions of alkenes with halogens, including how the C=C bond reacts with Br₂ and Cl₂.
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Hydrogen Halide
Learn how hydrogen halides add across the C=C bond and how major products can form with unsymmetrical alkenes.
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Bromine Water
Review the bromine water test for unsaturation, including the colour change from orange to colourless.
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Hydrogen
Revise hydrogenation of alkenes, including conversion to alkanes using a nickel catalyst.
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Steam
Learn how steam adds to alkenes in hydration reactions to produce alcohols under suitable conditions.
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Summary map
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Alkenes Map
OCR A Level Chemistry A · 4.1.3 Alkenes
Every reaction on one A4 page: reagents, conditions and reaction type for each arrow, colour coded, with the key tests.
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Specification
Every specification point in this topic, in the exam board's own words. Rate how confident you are with each one.
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4.1.3
- a i
alkenes as unsaturated hydrocarbons containing a C=C bond comprising a π-bond (sideways overlap of adjacent p-orbitals above and below the bonding C atoms) and a σ-bond (overlap of orbitals directly between the bonding atoms) (see also 4.1.2 a)
Revise - b i
explanation of the trigonal planar shape around each carbon in the C=C of alkenes in terms of electron pair repulsion (see also 2.2.2 g–h, 4.1.2 b)
Revise - b ii
explanation of the bond angle around each carbon in the C=C of alkenes in terms of electron pair repulsion (see also 2.2.2 g–h, 4.1.2 b)
Revise - c (i) a
explanation of the term stereoisomers (compounds with the same structural formula but with a different arrangement in space)
Revise - c (i) b
explanation of the term E/Z isomerism (an example of stereoisomerism, in terms of restricted rotation about a double bond and the requirement for two different groups to be attached to each carbon atom of the C=C group)
Revise - c (i) c
explanation of the term cis–trans isomerism (a special case of E/Z isomerism in which two of the substituent groups attached to each carbon atom of the C=C group are the same)
Revise - d i
determination of possible E/Z stereoisomers of an organic molecule, given its structural formula
Revise - d ii
determination of possible cis–trans stereoisomers of an organic molecule, given its structural formula
Revise - f (i)
addition reactions of alkenes with hydrogen in the presence of a suitable catalyst, e.g. Ni, to form alkanes
Revise - f (ii) b
the use of bromine to detect the presence of a double C=C bond as a test for unsaturation in a carbon chain
Revise - f (iv)
addition reactions of alkenes with steam in the presence of an acid catalyst, e.g. H3PO4, to form alcohols
Revise - h
the mechanism of electrophilic addition in alkenes by heterolytic fission (see also 4.1.1 h–i)
Revise - i i
use of Markownikoff's rule to predict formation of a major organic product in addition reactions of H–X to unsymmetrical alkenes, e.g. H–Br to propene
Revise - i ii
the relative stabilities of carbocation intermediates in the mechanism of addition of H–X to unsymmetrical alkenes
Revise - j (i)
addition polymerisation of alkenes and substituted alkenes, including the repeat unit of an addition polymer deduced from a given monomer
Revise - j (ii)
addition polymerisation of alkenes and substituted alkenes, including identification of the monomer that would produce a given section of an addition polymer
Revise - k (i)
the benefits for sustainability of processing waste polymers by combustion for energy production
Revise - k (ii)
the benefits for sustainability of processing waste polymers by use as an organic feedstock for the production of plastics and other organic chemicals
Revise - k (iii)
the benefits for sustainability of processing waste polymers by removal of toxic waste products, e.g. removal of HCl formed during disposal by combustion of halogenated plastics (e.g. PVC)
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