Topic 15
Halogen Compounds
Topic 15 covers the production of halogenoalkanes by free-radical substitution, electrophilic addition and substitution of alcohols, their classification, nucleophilic substitution with NaOH(aq), KCN, NH₃ and aqueous silver nitrate, elimination with ethanolic NaOH, the Sₙ1 and Sₙ2 mechanisms with the inductive effects of alkyl groups, and the different reactivities of halogenoalkanes explained by C–X bond strengths.
Revision Notes
5 revision notes, in the order the specification teaches them.
Reaction Types, Mechanisms and Nucleophiles
Organic reaction types and mechanisms: addition, elimination, substitution, oxidation, reduction, hydrolysis, polymerisation, curly arrows, heterolytic fission, electrophiles, nucleophiles and bond polarity.
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Halogenoalkanes: Naming, Classification and the C–X Bond
Halogenoalkanes: nomenclature and formulae, primary, secondary and tertiary, the polar carbon–halogen bond, bond enthalpies and uses.
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Nucleophilic Substitution Reactions
Nucleophilic substitution of halogenoalkanes: hydroxide, water, ammonia and cyanide as nucleophiles, conditions, products and the curly-arrow mechanism.
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Elimination Reactions of Halogenoalkanes
Elimination of halogenoalkanes: ethanolic KOH, hydroxide as a base, alkene products and isomers, substitution versus elimination.
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Rates of Hydrolysis and Bond Enthalpy
Rates of hydrolysis of halogenoalkanes: the silver nitrate experiment, precipitate colours, bond enthalpy trend for C–Cl, C–Br and C–I, and primary, secondary and tertiary comparison.
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Download, print and revise the reactions of this topic at a glance.
Summary maps
Download, print and revise the reactions of this topic at a glance.
Halogenoalkanes Map
Cambridge International AS & A Level Chemistry · Topic 15 Halogen compounds
Every reaction on one A4 page: reagents, conditions and reaction type for each arrow, colour coded, with the key tests.
Halogenoalkanes Summary Map
Cambridge International AS & A Level Chemistry · Topic 15 Halogen compounds
The whole topic on one A4 page: names, classes and nucleophiles, making halogenoalkanes, nucleophilic substitution, SN1 and SN2, elimination, and rates of hydrolysis.
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Specification
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15.1.1
- a i
recall the reaction (reagents and conditions) by which halogenoalkanes can be produced: the free-radical substitution of alkanes by Cl2 in the presence of ultraviolet light, as exemplified by the reactions of ethane
Revise - a ii
recall the reaction (reagents and conditions) by which halogenoalkanes can be produced: the free-radical substitution of alkanes by Br2 in the presence of ultraviolet light, as exemplified by the reactions of ethane
Revise - b i
recall the reaction (reagents and conditions) by which halogenoalkanes can be produced: electrophilic addition of an alkene with a halogen, X2, at room temperature
Revise - b ii
recall the reaction (reagents and conditions) by which halogenoalkanes can be produced: electrophilic addition of an alkene with a hydrogen halide, HX(g), at room temperature
Revise - c i
recall the reaction (reagents and conditions) by which halogenoalkanes can be produced: substitution of an alcohol by reaction with HX(g)
Revise - c ii
recall the reaction (reagents and conditions) by which halogenoalkanes can be produced: substitution of an alcohol with KCl and concentrated H2SO4 or concentrated H3PO4
Revise - c iii
recall the reaction (reagents and conditions) by which halogenoalkanes can be produced: substitution of an alcohol with PCl3 and heat
Revise - c iv
recall the reaction (reagents and conditions) by which halogenoalkanes can be produced: substitution of an alcohol with PCl5
Revise - c v
recall the reaction (reagents and conditions) by which halogenoalkanes can be produced: substitution of an alcohol with SOCl2
Revise
15.1.2
15.1.3
- a
describe the nucleophilic substitution reaction of halogenoalkanes with NaOH(aq) and heat to produce an alcohol
Revise - b
describe the nucleophilic substitution reaction of halogenoalkanes with KCN in ethanol and heat to produce a nitrile
Revise - c
describe the nucleophilic substitution reaction of halogenoalkanes with NH3 in ethanol heated under pressure to produce an amine
Revise - d
describe the nucleophilic substitution reaction of halogenoalkanes with aqueous silver nitrate in ethanol as a method of identifying the halogen present as exemplified by bromoethane
Revise
15.1.4
- 15.1.4
describe the elimination reaction with NaOH in ethanol and heat to produce an alkene as exemplified by bromoethane
Revise
15.1.5
15.1.6
- c
recall that secondary halogenoalkanes tend to react by a mixture of the SN1 and SN2 mechanisms, depending on structure
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15.1.7
- a
describe the different reactivities of halogenoalkanes (with particular reference to the relative strengths of the C–X bonds as exemplified by the reactions of halogenoalkanes with aqueous silver nitrate)
Revise - b
explain the different reactivities of halogenoalkanes (with particular reference to the relative strengths of the C–X bonds as exemplified by the reactions of halogenoalkanes with aqueous silver nitrate)
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