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Chapter 16 The Chemistry of Benzene Derivatives

Chapter 16 The Chemistry of Benzene Derivatives. Morphine. Valium. Aromatic Hydrocarbons. Common sources: coal and petroleum Physical properties: Tend to be insoluble in water MP ’ s relatively high BP ’ s similar to molecules of similar structure and symmetry

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Chapter 16 The Chemistry of Benzene Derivatives

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  1. Chapter 16The Chemistry of Benzene Derivatives

  2. Morphine Valium

  3. Aromatic Hydrocarbons • Common sources: coal and petroleum • Physical properties: • Tend to be insoluble in water • MP’s relatively high • BP’s similar to molecules of similar structure and symmetry • Each additional C atom adds 20-30°C to the BP

  4. Common Nomenclature

  5. IUPAC Nomenclature • Monosubstituted benzenes are named as other hydrocarbons, with –benzene as the parent name • Alkyl-substituted benzenes (arenes) are named in two ways: • If the alkyl group has 6 or fewer carbons, it is named as the substituent and the benzene ring is the parent

  6. If the alkyl chain has more than 6 carbons, then the benzene ring is the substituent and is called a “phenyl” group • A phenyl group can be represented a few different ways • Don’t confuse a phenyl group with a benzyl group

  7. Disubstitued benzenes can be named in two ways: • Using o, m, or p • Using numbers

  8. Nomenclature • Principle groups • If a substituent has highest priority, it is assumed to be on carbon #1 • If none of the substituents has priority over the others, cite them in alphabetical order

  9. Numbering is required when more than two substituents are present • Recall priorities: carboxylic acid > anhydride > ester > acid halide > amide > nitrile > aldehyde > ketone > alcohol (phenol) > thiol > amine 16.1 Nomenclature of Benzene Derivatives

  10. Problems • Name the following compounds:

  11. Electrophilic Aromatic Substitution

  12. Halogenation of Benzene • Compare with the addition product for that of an alkene 16.4 Electrophilic Aromatic Substitution Reactions of Benzene

  13. Mechanism of Halogenation 16.4 Electrophilic Aromatic Substitution Reactions of Benzene

  14. Mechanism of Halogenation 16.4 Electrophilic Aromatic Substitution Reactions of Benzene

  15. Recall:

  16. Three Mechanistic Steps in EAS 1. Generation of an electrophile 2. Nucleophilic reaction of the p electrons of the aromatic ring with the electrophile 3. Loss of a proton from the carbocation to form a substituted aromatic compound

  17. Problem • Monobromination of toluene gives 3 products. Draw the entire mechanism for the formation of one product and draw the other two. • Draw the product(s):

  18. Nitration of Benzene • Mechanism: 16.4 Electrophilic Aromatic Substitution Reactions of Benzene

  19. Nitration of Benzene 16.4 Electrophilic Aromatic Substitution Reactions of Benzene

  20. Reduction of Nitro-substituted Benzene Rings to Arylamines • Also works with SnCl2

  21. Sulfonation of Benzene • Mechanism:

  22. Problems • Draw the reactants required to produce the molecule below: • Draw the products for each step:

  23. Friedel-Crafts Alkylation of Benzene • Compare the role of AlCl3 with that of FeBr3 in the bromination reaction

  24. Limitations to Friedel-Crafts Alkylation • R must be an alkyl halide • The benzene ring cannot have amino or strongly electron withdrawing substituents

  25. Reaction often does not stop after the first substitution • Rearrangement products are often produced

  26. Hydride Shift: • Alkyl Shift:

  27. Problems • Give the products for the following reactions:

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