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30. Hydrocarbons

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  1. 30.1 Arenes

    1. 30.1.1Chemistry of arenes

      • Describe the chemistry of arenes as exemplified by the following reactions of benzene and methylbenzene: - (a) substitution reactions with Cl ₂ and with Br₂ with a catalyst, Al Cl ₃ or Al Br₃, to form halogenoarenes (aryl halides) - (b) nitration with a mixture of conc. HNO₃ and conc. H₂SO₄ at a temperature between - 25 °C and 60 °C - (c) Friedel–Crafts alkylation by CH₃Cl and Al Cl ₃ and heat - (d) Friedel–Crafts acylation by CH₃COCl and Al Cl ₃ and heat - (e) complete oxidation of the side-chain using hot alkaline KMnO₄ and then dil. acid to give a benzoic acid - (f) hydrogenation of the benzene ring using H₂ and Pt/Ni catalyst and heat to form a cyclohexane ring

    2. 30.1.2Mechanism: electrophilic substitution in arenes

      • Describe the mechanism of electrophilic substitution in arenes: - (a) as exemplified by the formation of nitrobenzene and bromobenzene - (b) with regards to the effect of delocalisation (aromatic stabilisation) of electrons in arenes to explain the predomination of substitution over addition

    3. 30.1.3Whether halogenation will occur

      • Predict whether halogenation will occur in the side-chain or in the aromatic ring in arenes depending on reaction conditions

    4. 30.1.4In the electrophilic substitution of arenes,

      • Describe that in the electrophilic substitution of arenes, different substituents direct to different ring positions (limited to the directing effects of –NH₂, –OH, –R, –NO₂, –COOH and –COR)