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Higher Chemistry

Higher Chemistry. Carboxylic Acids. Carboxylic Acids. A carboxylic acid Contains a carboxyl group, which is a carbonyl group (C=O) attached to a hydroxyl group ( — OH). Has the carboxyl group on carbon 1. carbonyl group O  CH 3 — C — OH hydroxyl group or CH 3 CO OH

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Higher Chemistry

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  1. Higher Chemistry Carboxylic Acids

  2. Carboxylic Acids A carboxylic acid • Contains a carboxyl group, which is a carbonyl group (C=O) attached to a hydroxyl group (—OH). • Has the carboxyl group on carbon 1. carbonyl group O  CH3 —C—OHhydroxyl group or CH3COOH carboxyl group

  3. Models of Carboxylic Acids • The three-dimensional models show the geometry of atoms in carboxylic acid molecules.

  4. IUPAC Names The IUPAC names of carboxylic acids • Replace the -e in the alkane name with -oic acid. CH4 methane HCOOH methanoic acid CH3—CH3 ethane CH3—COOH ethanoic acid • Number substituents from the carboxyl carbon 1. CH3 O | ║ CH3—CH—CH2—C—OH 4 3 2 1 3-methylbutanoic acid

  5. Common Names The common names of simple carboxylic acids • Are formic acid (1C), acetic acid (2C), propionic acid (3C), and butyric acid (4C). HCOOH formic acid CH3—COOH acetic acid • Locate substituents using , , γ for the carbon atoms adjacent to the carboxyl carbon. CH3 γ | CH3—CH—CH2—COOH 3-methylbutanoic acid (-methylbutryic acid)

  6. Alpha Hydroxy Acids Alpha hydroxy acids (AHAs) • Occur naturally in fruit, milk, and sugarcane. • Are used in skin care products.

  7. Names and Sources of Some Carboxylic Acids TABLE 16.1

  8. Common Carboxylic Acids Methanoic acid (formic acid) O ║ H─C─OH ethanoic acid (acetic acid) O ║ CH3─C─OH

  9. Aromatic Carboxylic Acids Benzoic acid • Is the aromatic carboxylic acid. • Locates substituents by assigning 1 to the carbon attached to the carboxyl group. • Has common names that assign prefixes ortho, meta, and para for 2 substituents. ortho 1, 2 location meta 1, 3 location para 1, 4 location

  10. Aromatic Carboxylic Acids benzoic acid 3-chlorobenzoic acid 4-aminobenzoic acid m-chlorobenzoic acid p-aminobenzoic acid

  11. Learning Check Give the IUPAC and common names: A. CH3—COOH CH3 | B. CH3—CH—COOH C.

  12. Solution A. CH3—COOH ethanoic acid (acetic acid) CH3 | B. CH3—CH—COOH 2-methylpropanoic acid (-methylpropionic acid) C. 2-bromobenzoic acid (o-bromobenzoic acid)

  13. Learning Check Give the IUPAC and common names for the following: A. CH3─CH2─COOH CH3 | B. CH3─CH─CH2─COOH C.

  14. Solution A. CH3─CH2─COOH propanoic acid (propionic acid) CH3 | B. CH3─CH─CH2─COOH 3-methylbutanoic acid (β-methylbutyric acid) C. 3-bromobenzoic acid (m-bromobenzoic acid)

  15. Preparation of Carboxylic Acids • Carboxylic acids can be prepared by oxidizing primary alcohols or aldehydes. • The oxidation of ethanol produces ethanoic acid (acetic acid). OH O O | [O] || [O] || CH3—CH2 CH3—C—HCH3—C—OH ethanol ethanal ethanoic acid (ethyl alcohol) (acetaldehyde) (acetic acid)

  16. Learning Check What alcohol could be used to prepare the following: 1. butanoic acid 2. propanoic acid

  17. Solution What alcohol could be used to prepare the following: [O] [O] 1. butanol butanal butanoic acid [O] [O] 2. 1-propanol propanal propanoic acid

  18. Properties of Carboxylic Acids

  19. Polarity of Carboxylic Acids Carboxylic acids • Are strongly polar. • Have two polar groups: hydroxyl (−OH) and carbonyl (C=O). δ- O ║δ+δ- δ+ CH3CO H

  20. Boiling Points of Carboxylic Acids The boiling points of carboxylic acids • Are higher than alcohols, ketones, and aldehydes of similar mass. • Are high because they form dimersin which hydrogen bonds form between the polar groups in the two carboxyl groups. O H—O || | CH3—C C—CH3 | || O—H O A dimer of acetic acid

  21. Comparison of Boiling Points Compound Molar Mass Boiling Point O ║ CH3−CH2−C−H 58 49°C CH3−CH2−CH2−OH 60 97°C O ║ CH3−C−OH 60 118°C

  22. Solubility in Water Carboxylic acids • Form hydrogen bonds with many water molecules. • With 1-4 carbon atoms are very soluble in water. Water molecules

  23. Boiling Points and Solubility TABLE 16.2

  24. Acidity of Carboxylic Acids Carboxylic acids • Are weak acids. • Ionize in water to produce carboxylate ions and hydronium ions. O O ║ ║ CH3−C−OH + H2O CH3−C−O– + H3O+

  25. Acid Dissociation Constants Carboxylic acids • Have small Ka values. • Exist mostly as molecules and a few ions in aqueous solutions. TABLE 16.3

  26. Neutralization of Carboxylic Acids Carboxylic acid salts • Are a product of the neutralization of a carboxylic acid with a strong base. CH3—COOH + NaOH CH3—COO– Na+ + H2O acetic acid sodium acetate (carboxylic acid salt) • Areused as preservatives and flavor enhancers.

  27. Learning Check Write the equation for the reaction of propanoic acid with A. water B. KOH

  28. Solution Write the equation for the reaction of propanoic acid with A. water CH3—CH2—COOH + H2O CH3—CH2—COO– + H3O+ B. KOH CH3—CH2—COOH + KOH CH3—CH2—COO– K+ + H2O

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