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National 5 Chemistry

National 5 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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National 5 Chemistry

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  1. National 5 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

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