6.1.1
Aromatic
Compounds
Section 6.1.1 covers the Kekulé and delocalised models of benzene and the evidence from bond lengths, enthalpy of hydrogenation and resistance to reaction; naming substituted aromatic compounds; nitration, halogenation and Friedel–Crafts reactions with a halogen carrier and the mechanisms of nitration and halogenation; why benzene resists bromination compared with alkenes; unfamiliar electrophilic substitutions; the weak acidity, bromination and nitration of phenols and why phenol reacts more readily than benzene; and the 2-, 4- and 3-directing effects of substituents in synthesis.
Revision Notes
9 revision notes, in the order the specification teaches them.
Structure and Bonding in Benzene
The structure and bonding of benzene: the Kekulé and delocalised models, p-orbital overlap, the π system and how benzene is represented.
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Evidence for the Structure of Benzene
The evidence for the structure of benzene: hydrogenation enthalpies, delocalisation energy, bond lengths and resistance to addition.
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Naming Aromatic Compounds
Naming substituted aromatic compounds: IUPAC rules, ring numbering, the phenyl group and worked examples.
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Electrophilic Substitution in Benzene
Electrophilic substitution in benzene: substitution versus addition, the general mechanism and the delocalised intermediate.
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Nitration of Benzene
The nitration of benzene: reagents and conditions, generation of NO₂⁺, the mechanism and the role of sulfuric acid.
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Halogenation of Benzene
The halogenation of benzene: the halogen carrier, generation of the halogen electrophile and the electrophilic substitution mechanism.
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Friedel–Crafts Alkylation and Acylation
Friedel–Crafts alkylation and acylation of benzene: AlCl₃ halogen carrier, the electrophile and the mechanism.
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Phenol: Acidity and Electrophilic Substitution
Phenol: the activated ring, bromination to 2,4,6-tribromophenol, weak acidity and nitration, compared with benzene.
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Directing Effects in Electrophilic Substitution
Directing effects in aromatic substitution: 2,4-directing and 3-directing groups, predicting products and planning synthesis.
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Benzene Map
OCR A Level Chemistry A · 6.1.1 Aromatic compounds
Every reaction on one A4 page: reagents, conditions and reaction type for each arrow, colour coded, with the key tests.
Phenol Map
OCR A Level Chemistry A · 6.1.1 Aromatic compounds
Every reaction on one A4 page: reagents, conditions and reaction type for each arrow, colour coded, with the key tests.
Benzene Structure Map
OCR A Level Chemistry A · 6.1.1 Benzene
All of the benzene section on one A4 page: the models, the evidence, stability, naming and uses.
Substitution and Directing Map
OCR A Level Chemistry A · 6.1.1 Substitution, phenol and directing effects
All of the substitution section on one A4 page: nitration, halogenation, Friedel-Crafts, phenol and directing.
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6.1.1
- a ii
the delocalised model for benzene in terms of p-orbital overlap forming a delocalised π-system
Revise - a iii
the comparison of the Kekulé model of benzene with the subsequent delocalised models for benzene
Revise - b i
the experimental evidence for a delocalised, rather than Kekulé, model for benzene in terms of bond lengths (see also 6.1.1 f)
Revise - b ii
the experimental evidence for a delocalised, rather than Kekulé, model for benzene in terms of enthalpy change of hydrogenation (see also 6.1.1 f)
Revise - b iii
the experimental evidence for a delocalised, rather than Kekulé, model for benzene in terms of resistance to reaction (see also 6.1.1 f)
Revise - d (i)
the electrophilic substitution of aromatic compounds with concentrated nitric acid in the presence of concentrated sulfuric acid
Revise - d (ii)
the electrophilic substitution of aromatic compounds with a halogen in the presence of a halogen carrier
Revise - d (iii) a
the electrophilic substitution of aromatic compounds with a haloalkane in the presence of a halogen carrier (Friedel–Crafts reaction)
Revise - d (iii) b
the electrophilic substitution of aromatic compounds with an acyl chloride in the presence of a halogen carrier (Friedel–Crafts reaction)
Revise - d (iii) c
the importance of the Friedel–Crafts reaction to synthesis by formation of a C–C bond to an aromatic ring (see also 6.2.4 d)
Revise - e ii
the mechanism of electrophilic substitution in arenes for halogenation (see also 4.1.1 h–i)
Revise - f
the explanation of the relative resistance to bromination of benzene, compared with alkenes, in terms of the delocalised electron density of the π-system in benzene compared with the localised electron density of the π-bond in alkenes (see also 4.1.3 a, 6.1.1 a)
Revise - g i
the interpretation of unfamiliar electrophilic substitution reactions of aromatic compounds
Revise - g ii
prediction of mechanisms of unfamiliar electrophilic substitution reactions of aromatic compounds
Revise - h i
the weak acidity of phenols shown by the neutralisation reaction with NaOH (see also 5.1.3 b)
Revise - h ii
the weak acidity of phenols shown by the absence of reaction with carbonates (see also 5.1.3 b)
Revise - i (i)
the electrophilic substitution reaction of phenol with bromine to form 2,4,6-tribromophenol
Revise - i (ii)
the electrophilic substitution reaction of phenol with dilute nitric acid to form a mixture of 2-nitrophenol and 4-nitrophenol
Revise - j
the relative ease of electrophilic substitution of phenol compared with benzene, in terms of electron pair donation to the π-system from an oxygen p-orbital in phenol (see also 4.1.3 a)
Revise - k i
the 2- and 4-directing effect of electron-donating groups (OH, NH2) in electrophilic substitution of aromatic compounds
Revise - k ii
the 3-directing effect of electron-withdrawing groups (NO2) in electrophilic substitution of aromatic compounds
Revise - l ii
the importance of directing effects to organic synthesis (see also 6.2.5 Organic Synthesis)
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