Chapter 17 Carbonyl Compounds I Reactions of Carboxylic Acids and Carboxylic Acid Derivatives - PowerPoint PPT Presentation

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Chapter 17 Carbonyl Compounds I Reactions of Carboxylic Acids and Carboxylic Acid Derivatives
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Chapter 17 Carbonyl Compounds I Reactions of Carboxylic Acids and Carboxylic Acid Derivatives

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  1. Organic Chemistry 6th Edition Paula Yurkanis Bruice Chapter 17 Carbonyl Compounds I Reactions of Carboxylic Acids and Carboxylic Acid Derivatives

  2. Class I Carbonyl Compounds

  3. Class II Carbonyl Compounds

  4. Nomenclature of Carboxylic Acids

  5. In systematic nomenclature, the carbonyl carbon is always C-1 In common nomenclature, the carbon next to the carbonyl is the a-carbon

  6. The functional group of a carboxylic acid is called a carboxyl group

  7. Naming Cyclic Carboxylic Acid

  8. Salts of Carboxylic Acids

  9. Acyl Halides Acid Anhydrides

  10. Esters

  11. Cyclic esters are known as lactones:

  12. Amides If a substituent is bonded to the nitrogen, the name of the substituent is stated first:

  13. Cyclic amides are known as lactams:

  14. Nitriles

  15. Structures of Carboxylic Acids and Carboxylic Acid Derivatives

  16. Two major resonance contributors in esters, carboxylic acids, and amides:

  17. Carboxylic acids have relatively high boiling points because… Amides have the highest boiling points:

  18. Naturally Occurring Carboxylic Acids and Carboxylic Acid Derivatives

  19. The reactivity of carbonyl compounds resides in the polarity of the carbonyl group:

  20. The tetrahedral intermediate is a transient species that eliminates the leaving group Y– or the nucleophile Z–: This is a nucleophilic acyl substitution reaction

  21. Z– will be expelled if it is a much weaker base than Y–; that is, Z– is a better leaving group than Y– (k–1 >> k2):

  22. Y– will be expelled if it is a weaker base than Z–; that is, Y– is a better leaving group than Z– (k2 >> k–1):

  23. Both reactant and product will be present if Y– and Z– have similar leaving abilities:

  24. Reaction Coordinate Diagrams for Nucleophilic Acyl Substitution Reactions (a) the Nu– is a weaker base (b) the Nu– is a stronger base (c) the Nu– and the leaving group have similar basicities

  25. A Molecular Orbital Description of How Carbonyl Compounds React

  26. The reactivity of a carboxylic acid derivative depends on the basicity of the substituent attached to the acyl group:

  27. Electron withdrawal increases the carbonyl carbon’s susceptibility to nucleophilic attack: The weaker the basicity of Y, the greater the reactivity:

  28. Weak bases are easier to expel when the tetrahedral intermediate collapses:

  29. A carboxylic acid derivative can be converted only into a less reactive carboxylic acid derivative:

  30. The tetrahedral intermediate eliminates the weaker base:

  31. If the nucleophile is neutral…

  32. A base is required to trap the HCl product Reactions of Acyl Halides Suitable bases include triethylamine (TEA) and pyridine

  33. TEA Excess amine traps HCl

  34. Formation of Amides from Acyl Halides Tertiary amines cannot form amides

  35. Reactions of Acid Anhydrides Acid anhydrides do not react with sodium chloride or with sodium bromide because Cl– and Br– are weaker bases than acetate

  36. Anhydride reactions are facilitated by acid or base catalysts

  37. Mechanism for the conversion of an acid anhydride into an ester (and a carboxylic acid): Elimination facilitated by protonation Addition facilitated by protonation In the absence of an acid catalyst, the reaction is sluggish, but the reaction speeds up as acid products are formed

  38. Reactions of Esters

  39. Phenyl esters are more reactive than alkyl esters because phenolate ions are weaker bases than alkoxide ions:

  40. Hydrolysis of an ester with primary or secondary alkyl groups can be catalyzed by an acid The carbonyl oxygen is first protonated, Because…

  41. There are no negatively charged species in the reaction:

  42. Excess water will force the equilibrium to the right Alcohols that have low boiling points can be removed by distillation as they are formed

  43. Acid catalyzes the reaction by…

  44. An acid catalyst can make a group a better leaving group: