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Chapter Sixteen

Chapter Sixteen. Carboxylic Acids, Esters, and Other Acid Derivatives. Carboxylic Acids. Fig. 16.1 The three simplest carboxylic acids: methanoic acid, ethanoic acid, and propanoic acid. Carboxylic Acids. Fig. 16.2 Benzoic acid molecule. Carboxylic Acids.

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Chapter Sixteen

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  1. Chapter Sixteen Carboxylic Acids, Esters, and Other Acid Derivatives

  2. Carboxylic Acids Fig. 16.1 The three simplest carboxylic acids: methanoic acid, ethanoic acid, and propanoic acid.

  3. Carboxylic Acids • Fig. 16.2 Benzoic acid molecule

  4. Carboxylic Acids Carboxylic acids contain the carboxyl group on carbon 1. • A carboxyl group is a carbonyl attached to a hydroxyl • Acts differently than an alcohol or a carbonyl compound O  CH3 —C—OH= CH3—COOH carboxyl group

  5. Naming Carboxylic Acids FormulaIUPACCommon alkan -oic acid prefix – ic acid HCOOH methanoic acid formic acid CH3COOH ethanoic acid acetic acid CH3CH2COOH propanoic acid propionic acid CH3CH2CH2COOH butanoic acid butyric acid

  6. Naming Rules • Identify longest chain containing the carboxyl group • (IUPAC) Number carboxyl carbon as 1 • (Common) Assign , , g to carbon atoms adjacent to carboxyl carbon CH3 | CH3 —CH—CH2 —COOH IUPAC 3-methylbutanoic acid Common -methylbutryic acid

  7. Aromatic Carboxylic Acids • Benzoic Acid is the aromatic carboxylic acid • Locates substituents by assigning 1 to the carbon with the carboxyl group 3-chlorobenzoic acid Benzoic acid 4-methylbenzoic acid

  8. Properties of Carboxylic Acids • Like alcohols, carboxylic acids form strong intermolecular hydrogen bonds. • Most carboxylic acids exist as dimers. • Boiling points higher than alkanes of similar MW. • Small carboxylic acids (1-4 carbons) are soluble in water

  9. Synthesis of Carboxylic Acids • Synthesized from aromatic rings, primary alcohols and aldehydes. Carboxylic Acid

  10. Oxidation of Aromatic Compounds • Benzene does not react with KMnO4. • Alkyl groups on the ring (-R) are readily oxidized though. • One product for all reactions.

  11. Oxidation of Aromatic Compoundswith KMnO4

  12. Oxidation of primary alcohols and aldehydes:

  13. Oxidation of alcohols to carboxylic acids.

  14. Properties • Carboxylic acids are weak acids • Stronger acids than alcohols CH3COOH + H2O CH3COO– + H3O+ • Neutralized by a base CH3COOH + NaOH CH3COO– Na+ + H2O

  15. Carboxylic acids are obviously acidic. • Stronger acids than alcohols, but weaker than mineral acids. • Will react with NaOH to give metal carboxylates. • There is a large range of acidities depending on the substituents on a carboxylic acid.

  16. Carboxylate Ions • The conjugate base of a carboxylic acid • Formed when a carboxylic acid loses a proton • Named by dropping the -ic acid ending and replacing it with –ate • CH3CH2COO- Propionate • CH3COO- Ethanoate (Acetate) • CH3CH2CH2COO- Butanoate

  17. Carboxylate Salts • An ionic compound in which the negative ion is a carboxylate ion • Naming: the positive ion is named first, followed by a separate word giving the name of the negative ion • Converted back to a carboxylic acid by the addition of a strong acid • CH3CH2COO-Na+ Sodium Propionate • CH3COO-K+ Potassium Ethanoate • CH3CH2CH2COO-Li+ Lithium Butanoate

  18. Carboxylic Acids Table 16.3

  19. Esters • Fig. 16.12 Methyl and ethyl esters of acetic acid.

  20. Ester In an ester, the H in the carboxyl group is replaced with an alkyl group O  CH3 —C—O—CH3=CH3—COO—CH3 ester group Sulfur analogs of esters are called thioesters (sulfur replaces the hydroxyl oxygen)

  21. Naming Esters • Name the alkyl from the alcohol –O- • Name the acid with the C=O with –ate acidalcohol O  methyl CH3 —C—O—CH3 Ethanoate methyl ethanoate (IUPAC) (acetate) methyl acetate (common)

  22. Esters

  23. Esterification: Preparation of Esters • Reaction of a carboxylic acid and alcohol • Acid catalyst O  H+ CH3 —C—OH+HO—CH2CH3 O  CH3 —C—O—CH2CH3 +H2O

  24. Hydrolysis: Breaking Up Esters • Esters react with water and acid catalyst • Split into carboxylic acid and alcohol O  H+ H—C—O—CH2CH3 +H2O O  H—C—OH + HO—CH2CH3

  25. Hydrolysis

  26. Saponification • Esters react with bases • Produce the salt of the carboxylic acid and alcohol O H2O CH3C—OCH2CH3 +NaOH O  CH3C—O– Na++ HOCH2CH3 salt of carboxylic acid • Saponification reactions produce soaps

  27. Soaps • Carboxylate salts

  28. The following figure represents soap. • Which end of the anion is hydrophobic?

  29. How does soap interact with grease?

  30. Dicarboxylic Acids

  31. The C2 dicarboxylic acid, oxalic acid, contributes to the tart taste of rhubarb stalks.

  32. Polyfunctional Carboxylic Acids • Carboxylic acids that contain one or more additional functional groups • Unsaturated acids • Contain a multiple bond • Hydroxy acids • Contains an additional hydroxyl group • Keto acids • Contains an additional carbonyl group • Many monoacids and polyfunctional carboxylic acids are intermediates in metabolic reactions

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