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CARBOXYLIC ACIDS

CARBOXYLIC ACIDS. Properties and Synthesis. NOMENCLATURE. IUPAC NOMENCLATURE. -oic acid IUPAC ending -carboxylic acid IUPAC ending for ring compounds. Naming. 3-Methylbutanoic acid b -Methylbutyric acid Isovaleric acid. 2-Chloropentanoic acid a -Chlorovaleric acid.

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CARBOXYLIC ACIDS

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  1. CARBOXYLIC ACIDS Properties and Synthesis

  2. NOMENCLATURE

  3. IUPAC NOMENCLATURE • -oic acid IUPAC ending • -carboxylic acid IUPAC ending for ring compounds

  4. Naming 3-Methylbutanoic acid b-Methylbutyric acid Isovaleric acid 2-Chloropentanoic acid a-Chlorovaleric acid

  5. 4-Aminobutanoic Acid g-Aminobutyric Acid “GABA” Naming 2-Methylpropanoic acid a-Methylpropionic acid Isobutyric acid

  6. More Naming Benzoic acid Benzenecarboxylic acid Cyclohexanecarboxylic acid

  7. Common Names

  8. SYNTHESIS OF CARBOXYLIC ACIDS

  9. Oxidation of Primary Alcohols with KMnO4 twoa-hydrogens + MnO2 precipitate

  10. Oxidation of Primary Alcohols with K2Cr2O7

  11. Oxidation of Side Chains Example D KMnO4

  12. Carbonation of Grignard Reagents ( or Alkyllithium Compounds ) ( R-Li )

  13. Formation of Nitriles and Hydrolysis DMSO H2SO4 H2O SN2 heat

  14. SYNTHESIS OF CARBOXYLIC ACIDS ( DUE TO LACK OF SPACE REACTION CONDITIONS ARE ABBREVIATED) ( benzene = R sidechain = R’ ) KMnO4 KMnO4 KMnO4 CrO3 or KMnO4 H2SO4 CrO3 H2O H2SO4 H2SO4 DIBAL or NaCN acetone Rosenmund CO2 H2O KMnO4 H2SO4 SOCl2 Li or Mg H2O or Chap 19 This is all stuff you know!

  15. Physical Properties of Carboxylic Acids

  16. Physical Properties of Some Organic Compounds

  17. ACIDITY

  18. Carboxylate Ion Formation They are acids, ya know ! carboxylic acid carboxylate ion pKa»5

  19. Protonation and Deprotonation of a Carboxylic Acid .. + .. .. .. : : .. - .. NaOH H2SO4 .. : .. .. .. : H2SO4 + .. .. : .. equivalent structures due to resonance +

  20. Electron-withdrawing Groups: • strengthen acids • weaken bases • Electron-releasing Groups: • weaken acids • strengthen bases

  21. Substituents with Electron-Withdrawing Resonance ( - R ) Effects X Y -R substituents strengthen acids and weaken bases

  22. .. Y Substituents with Electron-Releasing Resonance ( + R ) Effects hydroxy alkoxy mercapto acyloxy methyl alkyl dialkylamino amino fluoro chloro bromo iodo +R substituents weaken acids and strengthen bases

  23. Substituents with Electron-Withdrawing ( - I ) Inductive Effects X carboxyl cyano alkoxycarbonyl sulfonic acid alkoxy acyl dialkylamino hydroxyl fluoro mercapto bromo amino iodo chloro trimethylammonium nitro -I substituents strengthen acids and weaken bases

  24. Substituents with Electron-Releasing Inductive ( + I ) Effects R methyl alkyl carboxylate oxide +I substituents weaken acids and strengthen bases

  25. increasing acidity

  26. ortho ortho meta meta para para Benzoic Acid: pKa = 4.19

  27. 4.08 4.06 4.48 4.46 2.97 Benzoic Acid: pKa = 4.19

  28. Benzoic Acid: pKa = 4.19

  29. Acidity of Carboxylic Acids

  30. Reactions of Carboxylic Acids • Nucleophiles that are also strong bases react with carboxylic acids by removing a proton first, before any nucleophilic substitution reaction can take place.

  31. Nucleophilic acyl substitution reactions of carboxylic acids

  32. Treatment of a carboxylic acid with thionyl chloride (SOCl2) affords an acid chloride. • This is possible because thionyl chloride converts the OH group of the acid into a better leaving group, and because it provides the nucleophile (Cl¯) to displace the leaving group.

  33. Although carboxylic acids cannot readily be converted into anhydrides, dicarboxylic acids can be converted to cyclic anhydrides by heating to high temperatures. • This is a dehydration reaction because a water molecule is lost from the diacid.

  34. ESTERIFIKASI ASAM KARBOKSILAT

  35. Esterification of a carboxylic acid occurs in the presence of acid but not in the presence of base. • Base removes a proton from the carboxylic acid, forming the carboxylate anion, which does not react with an electron-rich nucleophile.

  36. Intramolecular esterification of - and -hydroxyl carboxylic acids forms five- and six-membered lactones.

  37. Carboxylic acids cannot be converted into amides by reaction with NH3 or an amine because amines are bases, and undergo an acid-base reaction to form an ammonium salt before nucleophilic substitution occurs. • However, heating the ammonium salt at high temperature (>100°C) dehydrates the resulting ammonium salt of the carboxylate anion to form an amide, although the yield can be low.

  38. The overall conversion of RCOOH to RCONH2 requires two steps: • [1] Acid-base reaction of RCOOH with NH3 to form an ammonium salt. • [2] Dehydration at high temperature (>100°C).

  39. A carboxylic acid and an amine readily react to form an amide in the presence of an additional reagent, dicyclohexylcarbodimide (DCC), which is converted to the by-product dicyclohexylurea in the course of the reaction.

  40. DCC is a dehydrating agent. • The dicyclohexylurea by-product is formed by adding the elements of H2O to DCC. • DCC promotes amide formation by converting the carboxy group OH group into a better leaving group.

  41. Carboxylic Acid Derivatives

  42. Related Carbonyl Derivatives

  43. Related Carbonyl Derivatives

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