4.2.2
Haloalkanes
Section 4.2.2 covers hydrolysis of haloalkanes by aqueous alkali and by water with silver nitrate in ethanol, the definition of a nucleophile, the mechanism of nucleophilic substitution for primary haloalkanes, the trend in rates of hydrolysis explained by carbon–halogen bond enthalpies, and the production of halogen radicals from CFCs and the catalysed breakdown of ozone by Cl• and •NO.
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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Haloalkanes: Naming, Classification and the C–X Bond
Haloalkanes: 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 haloalkanes: hydroxide, water, ammonia and cyanide as nucleophiles, conditions, products and the curly-arrow mechanism.
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Rates of Hydrolysis and Bond Enthalpy
Rates of hydrolysis of haloalkanes: 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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CFCs and the Ozone Layer
CFCs and the ozone layer: chlorine radicals, the equations for ozone decomposition, the catalytic cycle, legislation and HFC alternatives.
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Haloalkanes Map
OCR A Level Chemistry A · 4.2.2 Haloalkanes
Every reaction on one A4 page: reagents, conditions and reaction type for each arrow, colour coded, with the key tests.
Haloalkanes Summary Map
OCR A Level Chemistry A · 4.2.2 Haloalkanes
The whole section on one A4 page: reaction types and nucleophiles, names and classes, hydrolysis by hydroxide and water, rates of hydrolysis, CFCs and UV, and ozone breakdown.
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4.2.2
- a (ii) a
hydrolysis of haloalkanes in a substitution reaction by water in the presence of AgNO3 and ethanol
Revise - a (ii) b
use of hydrolysis by water in the presence of AgNO3 and ethanol to compare experimentally the rates of hydrolysis of different carbon–halogen bonds
Revise - c
the mechanism of nucleophilic substitution in the hydrolysis of primary haloalkanes with aqueous alkali (see also 4.1.1 h–i)
Revise - d
explanation of the trend in the rates of hydrolysis of primary haloalkanes in terms of the bond enthalpies of carbon–halogen bonds (C–F, C–Cl, C–Br and C–I)
Revise - e i
production of halogen radicals by the action of ultraviolet (UV) radiation on CFCs in the upper atmosphere
Revise - e ii
the catalysed breakdown of the Earth's protective ozone layer resulting from halogen radicals
Revise - e (ii)
equations to represent the catalysed breakdown of ozone by Cl· and other radicals e.g. ·NO
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