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Reactions of arenes

Reactions of arenes. L.O.: Outline the mechanism of nitration. Outline the mechanism of of acylation. Identify the reactive intermediates involved in nitration and acylation. Name the mechanisms of both reactions. STRUCTURE OF BENZENE. STRUCTURE OF BENZENE. STRUCTURE OF BENZENE. NITRATION.

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Reactions of arenes

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  1. Reactions of arenes L.O.: • Outline the mechanism of nitration. • Outline the mechanism of of acylation. • Identify the reactive intermediates involved in nitration and acylation. • Name the mechanisms of both reactions.

  2. STRUCTURE OF BENZENE

  3. STRUCTURE OF BENZENE

  4. STRUCTURE OF BENZENE

  5. NITRATION nitrobenzene Conditions conc HNO3 conc H2SO4 catalyst 50ºC

  6. NITRATION – ELECTROPHILIC SUBSTITUTION HNO3 + 2 H2SO4 + H3O+ + 2 HSO4- + NO2 + NO2 NO2 Formation of electrophile nitronium ion Reaction of electrophile with aromatic compound NO2 + -H H +

  7. NITRATION Equation (name product) Conditions Mechanism

  8. NITRATION 2-methylnitrobenzene Conditions conc HNO3 conc H2SO4 catalyst 50ºC

  9. NITRATION Uses of nitro compounds: 1) as explosives 2) to make aromatic amines (used to make dyes) 1,3,5-trinitrotoluene TNT

  10. Name the mechanism for this reaction. Electrophilic substitution

  11. Draw the electron arrangement (dot-cross diagram) of aluminium chloride.

  12. FRIEDEL-CRAFTS ACYLATION aromatic ketone Conditions AlCl3 catalyst

  13. FRIEDEL-CRAFTS ACYLATION WARNING! - do not mix Friedel-Crafts acylation & other acylations (needs AlCl3) Swap H on benzene ring for acyl group Swap H on O/N for acyl group

  14. FRIEDEL-CRAFTS ACYLATION WARNING! - Classic question to test this H replaced is on N not benzene ring. This is NOT Friedel-Crafts acylation!

  15. FRIEDEL-CRAFTS ACYLATION – ELECTROPHILIC SUBSTITUTION Formation of electrophile O AlCl3 + RCOCl AlCl4 + – C R + acylium ion OR O O O O – + R-C-O-AlCl3 C R AlCl3 + R-C-O-C-R + acylium ion

  16. FRIEDEL-CRAFTS ACYLATION – ELECTROPHILIC SUBSTITUTION O R C C + Reaction of electrophile with aromatic compound O O C R + R -H H + Regeneration of catalyst AlCl4 – + H+ AlCl3+ HCl or O O – R-C-O-AlCl3 + H+ R-C-OH + AlCl3

  17. FRIEDEL-CRAFTS ACYLATION Equation Conditions Mechanism

  18. FRIEDEL-CRAFTS ACYLATION Conditions AlCl3 catalyst

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