CHEM 222 Chapter Notes - Chapter 15: Clemmensen Reduction, Acyl Group, Electrophilic Aromatic Directing Groups
20 Jan 2017
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15. 1 electrophilic aromatic substitution reactions: electrophilic aromatic substitutions: (ears) electrophile replaces one of the hydrogen atoms of the ring. 15. 3 halogenation of benzene: benzene reacts with benzene and chlorine in presence of lewis acid to give halogenated substitution products (good yield, lewis acid makes halogen a stronger nucleophile. Iodine so unreactive that reaction must be carried out in presence of oxidizing agent (i. e. nitric acid) Increase in conc. sulfuric increases [electrophile] no2 reaction. 15. 5 sulfonation of benzene: all steps are in equilibria, so overall reaction is reversible, benzene + h2so4 --> benzene-so3h + water. If want to favor products, use concentrated or fuming sulfuric acid. If want favor reactants (desulfonate ring) use dilute sulfuring acid and steam. 15. 6 friedel-crafts alkylation: friedel-crafts alkylation overall equation. Initial formation of carbocation, which then acts as electrophile and attacks the benzene ring to form arenium ion: arenium ion loses proton.
