organic-2-organic-chemistry-mcmurry-25-ch-16-chemistry-of-benzene-electrophilic-aromatic-substitutio

Organic-2-organic-chemistry-mcmurry-25-ch-16-chemistry-of-benzene-electrophilic-aromatic-substitutio

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www.clutchprep.com ORGANIC - MCMURRY 8E CH. 16 - CHEMISTRY OF BENZENE: ELECTROPHILIC AROMATIC SUBSTITUTION
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CONCEPT: ELECTROPHILIC AROMATIC SUBSTITUTION GENERAL MECHANISM Benzene reacts with very few reagents. It DOES NOT undergo typical addition reactions. Why? If we can get benzene to react in a substitution reaction, this preserves aromaticity . Very strong electrophiles can temporarily disrupt aromaticity of benzene to create a substitution product. We call this electrophilic aromatic substitution or __________. This is the most important mechanism of benzene. EAS: General Mechanism ORGANIC - MCMURRY 8E CH. 16 - CHEMISTRY OF BENZENE: ELECTROPHILIC AROMATIC SUBSTITUTION Page 2
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CONCEPT: ELECTROPHILIC AROMATIC SUBSTITUTION REACTIONS EAS reactions require strong electrophiles to take place. Some of these will require catalysts . ORGANIC - MCMURRY 8E CH. 16 - CHEMISTRY OF BENZENE: ELECTROPHILIC AROMATIC SUBSTITUTION Page 3
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CONCEPT: GENERATING ELECTROPHILES EAS HALOGENATION EAS Bromination and Chlorination both require complexing with a Lewis Acid Catalyst before the reaction can begin. General Reaction: Mechanism: ORGANIC - MCMURRY 8E CH. 16 - CHEMISTRY OF BENZENE: ELECTROPHILIC AROMATIC SUBSTITUTION Page 4
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CONCEPT: GENERATING ELECTROPHILES EAS NITRATION EAS Nitration requires nitric acid to react with a catalytic acid to generate a strong nitronium ion electrophile. General Reaction: Mechanism: Reduction of Nitro Groups: Nitro groups can be reduced in the presence of many reducing agents to aniline. More on this in your amines chapter. ORGANIC - MCMURRY 8E CH. 16 - CHEMISTRY OF BENZENE: ELECTROPHILIC AROMATIC SUBSTITUTION Page 5
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CONCEPT: GENERATING ELECTROPHILES FRIEDEL-CRAFTS ALKYATION Friedel-Crafts Alkyation requires an alkyl halide to complex with a Lewis Acid Catalyst before the reaction can begin. Active electrophile is a carbocation Watch out for ________________________________ General Reaction: Mechanism: ORGANIC - MCMURRY 8E CH. 16 - CHEMISTRY OF BENZENE: ELECTROPHILIC AROMATIC SUBSTITUTION Page 6
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CONCEPT: GENERATING ELECTROPHILES FRIEDEL-CRAFTS ACYLATION Friedel-Crafts Acylation requires an acyl halide to complex with a Lewis Acid Catalyst before the reaction can begin. Active electrophile is an acylium ion General Reaction: Mechanism: ORGANIC - MCMURRY 8E CH. 16 - CHEMISTRY OF BENZENE: ELECTROPHILIC AROMATIC SUBSTITUTION Page 7
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CONCEPT: GENERATING ELECTROPHILES ANY CARBOCATION Popular carbocations include those catalyzed by hydrofluoric acid and promoted by boron trifluoride. Watch out for ________________________________ General Reaction: Mechanisms: ORGANIC - MCMURRY 8E CH. 16 - CHEMISTRY OF BENZENE: ELECTROPHILIC AROMATIC SUBSTITUTION Page 8
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CONCEPT: EAS MONOSUBSTITUTED BENZENE Substituents alter the electron density of benzene rings, affecting reactivity toward subsequent EAS in two ways: 1. Activity Effects ● Electron Donating Groups EDG’s ________________________ the ring toward reactions Electron Withdrawing Groups EWG’s _____________________ the ring toward reactions 2. Directing Effects Electron Donating Groups EDG’s tend to be _____________, ____________ directors
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