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AROMATIC SUBSTITUTION REACTIONS

AROMATIC SUBSTITUTION REACTIONS . NOMENCLATURE. Learn Nomeclature Either on Your Own or Use the Organic Nomeclature Software. 1-bromo-3-nitrobenzene. methylbenzene. (toluene). 1-chloro-3-methylbenzene. 1,4-dimethylbenzene. SOME SPECIAL NAMES. toluene. aniline. anisole.

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AROMATIC SUBSTITUTION REACTIONS

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  1. AROMATIC SUBSTITUTION REACTIONS

  2. NOMENCLATURE

  3. Learn Nomeclature Either on Your Own or Use the Organic Nomeclature Software 1-bromo-3-nitrobenzene methylbenzene (toluene) 1-chloro-3-methylbenzene 1,4-dimethylbenzene

  4. SOME SPECIAL NAMES toluene aniline anisole phenol o-xylene m-xylene benzoic acid p-xylene

  5. ortho, meta and para Positions m-nitrotoluene 3-nitrotoluene ipso 1 o- ortho 6 2 1-methyl-3-nitrobenzene meta m- 5 3 4 para p-dichlorobenzene p- 1,4-dichlorobenzene

  6. Compounds containing aromatic rings are often used in dyes, such as these for sale in a market in Nepal Source: Getty Images

  7. REVIEW OF BENZENE PROPERTIES

  8. Figure 22.11: The structure of benzene

  9. BENZENE RESONANCE Review Sections 6.8 - 6.14 KEKULE STRUCTURES Resonance Energy = 36 Kcal / mole All bonds are equivalent The ring is symmetric. Bond lengths are between a single and a double bond. Very Stable Less reactive than other groupings of atoms.

  10. . . H H . . . . H H H H All 2p orbitals overlap equally.

  11. BENZENE Isodensity surfaces - electron potential mapped in color. (van der Waal’s) Highest electron density is red. Color adjusted to enhance the pi system. Note the symmetry.

  12. BENZENE - DETERMINATION OF RESONANCE ENERGY cyclohexatriene (hypothetical) benzene RESONANCE ENERGY 36 kcal/mol cyclohexene -49.8 kcal/mol -85.8 kcal/mol (calculated) -28.6 kcal/mol cyclohexane

  13. REACTIVITY

  14. The “Double Bonds” in a Benzene Ring Do Not React Like Others Alkene Benzene no reaction + + no reaction + + no reaction + + no reaction + +

  15. Benzene is a Weak Base and Poor Nucleophile Stronger base + Readily donates electrons to an electrophile. alkene + Donation of electrons would interrupt ring resonance (36 kcal / mole). Weaker base A strong electrophile is required - and often a catalyst. benzene

  16. Benzene Reactivity Benzene requires a strong electrophile and a catalyst …..and then it undergoes substitution reactions, not addition. + + catalyst substitution compare: + no catalyst addition

  17. Some Substitution Reactions of Benzene Halogenation + Friedel-Crafts Alkylation + Friedel-Crafts Acylation + - + + Nitration + - Sulfonation +

  18. Blood Alcohol Level

  19. Alcohols and Water • alcohols are “monosubstituted” water, ROH, hydrocarbon radical, R, substituted for one of the hydrogen atoms in water, HOH • alcohols form hydrogen bonds to other alcohol molecules, increasing boiling point, and to water, making them very soluble in water

  20. Classes of Alcohols

  21. Oxidation of Alcohols primary alcohol  aldehyde  carboxylic acids RCH2OH  RCHO  RCOOH secondary alcohols  ketones RCHOHR’  RC=OR’ tertiary alcohols  No Reaction

  22. Large Molecules Containing Alcohol Groups

  23. More Large Molecules Containing Alcohol Groups

  24. Ethanol is being tested in selected areas as a fuel for automobiles Source: AP/Wide World Photos

  25. ALDEHYDES AND KETONES I

  26. STRUCTURE Aldehyde Ketone

  27. Cinnamaldehyde produces the characteristic odor of cinnamon Source: Visuals Unlimited

  28. NOMENCLATURE

  29. IUPAC Nomenclature of Ketones • Choose the longest continuous carbon chain that contains the carbonyl carbon • Number from the end of the chain closest to the carbonyl carbon • Ketone ending is -one Do the ketonessection of Organic Nomenclature program!

  30. EXAMPLES 2-Pentanone 4-Ethyl-3-hexanone

  31. 3-Isopropylcyclopentanone or 3-(1-Methylethyl)cyclopentanone

  32. KETONES Common, or Trivial, Names • Name each group attached to the carbonyl group as an alkyl group • Combine into a name, according to the pattern: alkyl alkyl’ ketone NOTE: This is not all one word!

  33. Example of Common Names Methyl propyl ketone Diethyl ketone

  34. SPECIAL CASES diphenyl ketone dimethyl ketone benzophenone acetone A common laboratory solvent and cleaning agent methyl phenyl ketone KNOW THESE acetophenone

  35. IUPAC Nomenclature of Aldehydes • Choose the longest continuous carbon chain that contains the carbonyl carbon • Number from the end of the chain closest to the carbonyl carbon (carbon #1!) • Aldehyde ending is -al Do the aldehydessection of Organic Nomenclature program.

  36. EXAMPLES aldehyde group is always carbon 1 pentanal 3 1 4 2 2-chloro-3-methylbutanal

  37. RECOGNIZE THESE Common Names of the Aldehydes

  38. SPECIAL CASES formaldehyde benzaldehyde KNOW THESE acetaldehyde

  39. Figure 22.13: Some common ketones and akdehydes

  40. Figure 22.14: Some carboxylic acids

  41. Computer-generated space-filling model of acetylsalicylic acid (aspirin) Source: Photo Researchers, Inc.

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