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Chapter 10 Carboxylic Acids

Chemistry 20. Chapter 10 Carboxylic Acids. Carboxylic Acids. A carboxylic acid contains a carboxyl group , which is a carbonyl group attach to a hydroxyl group. carbonyl group O  CH 3 — C — OH hydroxyl group or CH 3 CO OH carboxyl group. CH 3 CO 2 H.

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Chapter 10 Carboxylic Acids

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  1. Chemistry 20 Chapter 10 Carboxylic Acids

  2. Carboxylic Acids A carboxylic acid contains a carboxyl group, which is a carbonyl group attach to a hydroxyl group. carbonyl group O  CH3 —C—OHhydroxyl group or CH3COOH carboxyl group CH3CO2H

  3. Naming Carboxylic Acids • In the IUPAC name of carboxylic acids, the “-e” in the name of the longest chain is replaced by “-oic acid”. • The common names use prefixes “form-” and “acet-” for the first two carboxylic acids. • H-COOH methanoic acid formic acid • CH3-COOH ethanoic acid acetic acid • CH3-CH2-COOH propanoic acid • CH3-CH2-CH2-COOH butanoic acid

  4. O H H N C O O H 2 O H Naming Carboxylic Acids • Number the chain beginning with the carbon of the carboxyl group. • Because the carboxyl carbon is understood to be carbon 1, there is no need to give it a number. CH3 CH2 – CH3 1 3 1 2 CH3─CH─CH2─COOH CH3─CH2─CH─COOH 2-Ethylbutanoic acid 3-Methylbutanoic acid O 4 1 5 1 5-Hydroxylhexanoic acid 4-Aminobenzoic acid

  5. H O O H H O O H H O H O H O O H O H O H Naming Dicarboxylic Acids • Add the suffix “-dioic acid” to the name of the parent alkane that contains both carboxyl groups; thus, “-ane”becomes “-anedioic acid”. • The numbers of the carboxyl carbons are not indicated because they can be only at the ends of the chain. O O O 1 3 1 2 O Ehanedioic acid Propanedioic acid O O O O 5 1 1 1 6 4 O O Butanedioic acid Pentanedioic acid Hexanedioic acid

  6. Hydrogen bonding between two molecules d - d + O H O C C H H C C 3 3 O O H d + d - Physical properties of Carboxylic Acids • 1- The carboxyl group contains three polar covalent bonds; • C=O, C-O, and O-H. So they are so polar. • 2-Carboxylic acids have higher boiling points than other types of organic compounds (with the same molecular weight) because of hydrogen bonding. • 3- They are more soluble in water than alcohols, ethers, aldehydes, and ketones because of stronger hydrogen bonding. • 4- Liquid carboxylic acids have sharp and disagreeable odors. • 5- They taste sour (exist in pickle, lime, and lemon).

  7. Fatty Acids • Long, unbranched chain carboxylic acids and they are found in animal fats, vegetable oils, or phospholipids of biological membranes. • Most have between 12 and 20 carbons in an unbranched chain. • In most unsaturated fatty acids, the cis isomer is usually existed and the trans isomer is rare. • Unsaturated fatty acids have lower melting points than their saturated counterparts. Cis

  8. Fatty Acids Saturated fatty acids are solids at room temperature. Packed together  Maximum London dispersion forces

  9. Fatty Acids Unsaturated fatty acids are liquids at room temperature. Can not packed together  London dispersion forces Cis

  10. Esters In an ester, the H in the carboxyl group is replaced by an alkyl group. O  CH3 —C—O —CH3 ester group

  11. Soaps • Natural soaps are sodium or potassium salts of fatty acids. • They are prepared from a blend of tallow and coconut oils (triglycerides). • Triglycerides are triesters of glycerol. • the solid fats are melted with steam and the water insoluble triglyceride layer that forms on the top is removed. CH2 – CH – CH2 OH OH OH 1,2,3-Propanetriol (glycerol, glycerin)

  12. Soaps • Preparation of soaps begins by boiling the triglycerides with NaOH. The reaction that takes place is called saponification. • Boiling with KOH gives a potassium soap.

  13. Soaps Hydrophobic part: nonpolar Hydrophilic part: polar (remains in contact with environment)

  14. Soaps When soap is mixed with dirt (grease, oil, and …), soap micelles “dissolve” these nonpolar, water-insoluble molecules.

  15. Soaps • Natural soaps form water-insoluble salts in hard water. • Hard water contains Ca(II), Mg(II) and Fe(III) ions. Solution: Using Synthetic detergents. -SO3- (sulfonate) instead of COO- (carboxylate)

  16. Chemical properties of Carboxylic Acids 1- They are weak acids. Substituents of high electronegativity, especially -OH, -Cl, and -NH3+, near the carboxyl group increase the acidity of carboxylic acids.

  17. Chemical properties of Carboxylic Acids 2- Reaction with bases: They react with NaOH, KOH, NH3, and other strong bases to form water-soluble salts.

  18. O = LiAlH4, ether CH2OH COH H2O 3-cyclopentene- carboxylic acid 4-Hydroxymethyl- cyclopentene Chemical properties of Carboxylic Acids 3- Reduction: Resistant to reduction Using a powerful reducing agent: LiAlH4 (Lithium aluminum hydride). 1° alcohol

  19. Chemical properties of Carboxylic Acids 3- Fischer Esterification: - A carboxylic acid reacts with an alcohols to form an ester. - Using an acid catalyst such as concentrated sulfuric acid. The best way to prepare an ester.

  20. Heat Chemical properties of Carboxylic Acids 5- Decarboxylation: Loss of CO2 from a carboxyl group.

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