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Chem 1152: Ch. 15

Chem 1152: Ch. 15. Carboxylic Acids and Esters. Carboxylic Acids. O. C. COOH. CO 2 H. OH. Produce sour tastes in foods Acetic Acid (vinegar) Citric acid (lemons) Malic acid (apples). Esters are responsible for fragrant odors in fruits and flowers

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Chem 1152: Ch. 15

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  1. Chem 1152: Ch. 15 Carboxylic Acids and Esters

  2. Carboxylic Acids O C COOH CO2H OH Produce sour tastes in foods • Acetic Acid (vinegar) • Citric acid (lemons) • Malic acid (apples) Esters are responsible for fragrant odors in fruits and flowers • Used as flavoring agents and scents (perfume, deodorant) O C C O Esters

  3. Naming Carboxylic Acids • Identify the longest C chain including the carboxyl group. • Number the parent chain so that carboxyl C has lowest number. • So for monocarboxylic acids, this will be 1, and does not need to be numbered in naming. • Drop final –e (or –ene from benzene) from parent chain and replace with –oic acid.

  4. Sweat! Know common name and characteristics/uses of highlighted carboxylic acids Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

  5. Physical Properties of Carboxylic Acids Solubility • Highly-soluble at low MW (H-bonds with HOH) • Insoluble at high MW (7+ carbons) General order of Solubility Hydrocarbons < ethers < aldehydes and ketones < alcohols < carboxylic acids Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

  6. Physical Properties of Carboxylic Acids Boiling Points • Higher BP than alcohols due to formation of 2 H-bonds vs. 1 H-bond between like molecules. alcohol Carboxylic acid Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

  7. Carboxylic Acids: Acidity H+ Carboxylic acids weak acids: Only about 5% of acetic acid dissociates compared to ~100% for mineral acid (e.g., HCl) HCl + H2O  H3O+ + Cl- Reaction is reversible for carboxylic acids (not HCl) Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

  8. Acidity/Basicity H+ OH- acidic neutral basic 0 7 14 pH pH = -log[H+] • The pH of solution determines form of carboxylic acid • Ex. Carboxylate ion predominates at pH 7.4 (physiological pH) Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

  9. Carboxylic Acid Salts Reaction with base produces salt and water HCl + NaOH  H2O + NaCl Sodium carboxylate • Naming carboxylic salts • Name the metal first • Change the –ic acid ending of the acid name to -ate sodium ethanoate (sodium acetate) potassium benzoate Lithium 2-methylbenzoate

  10. Useful Carboxylic Acid Salts • Important component of soap • produced by hydrolysis of triglycerides (esters of fatty acids) • How soap is made from animal fat Sodium stearate Sodium benzoate • Food preservative Zinc 10-undecylenate • Used to treat athletes foot http://chemicalland21.com/lifescience/phar/ZINC%20UNDECYLENATE.htm

  11. Carboxylic Esters Ester linkage • Esterification: Carboxylic acids can react with alcohols to form esters • -OR’ group of alcohol forms ester linkage Ex. 1 H+, heat Ex. 2 Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

  12. Ester Reaction Products Relatively Poor Yields Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

  13. Important Esters • Polyesters: Polymers of esters • Formed by condensation polymerization (joining monomers, water byproduct) Symmetrical monomers Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

  14. Polyester Leisure Suits: Yeah… http://en.wikipedia.org/wiki/File:LeisureSuitConvention4.jpg

  15. Better Yield Reactions to Create Esters • More reactive than carboxylic acids • Non-reversible • Still use alcohol Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

  16. Specific Reactions with Acid Chlorides/Anhydrides Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

  17. Naming Esters • Esters may have common or IUPAC names • The first word of the name of an ester is the name of alkyl or aromatic group (R) • Change the –ic acid ending of the acid name to –ate (like naming carboxylic acid salts) • Parent contains the –COO group methyl ethanoate phenyl butanoate ethyl benzoate isopropyl methanoate methyl benzoate

  18. Ester Products/Names ethyl benzoate Carboxylic acid chloride Carboxylic acid chloride ethyl propanoate methyl benzoate isopropyl propanoate Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

  19. Ester Reactions: Hydrolysis • Reaction of ester with water to break ester linkage and produce alcohol and carboxylic acid • Reverse of esterification • Catalyzed by strong acids Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

  20. Ester Reactions: Saponification • Reaction of ester with water to break ester linkage and produce alcohol and carboxylic acid • Reverse of esterification • Done in solutions containing strong bases • Carboxylic acid converted to salt Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

  21. Saponification Products • Reaction of ester with water to break ester linkage and produce alcohol and carboxylic acid isopropyl propanoate sodium propanoate potassium benzoate ethyl benzoate Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

  22. Esters of Inorganic Acids • Alcohols can form esters by reaction with strong, inorganic acids (sulfuric, nitric and phosphoric) Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

  23. Production of Phosphoric Anhydrides • Alcohols can form esters by reaction with strong, inorganic acids (sulfuric, nitric and phosphoric) • Phosphoric most important • Forms linkage for DNA/RNA, ATP/ADP ADP Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

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