Carboxylic Acids and Carboxylic Acid Derivatives

1. Carboxylic Acids and Carboxylic Acid Derivatives Chapter 15 Pages 408-438

2. Structure of Carboxylic Acids • The carboxyl group is shown in red and may be written in the condensed form: -COOH. • The term carboxylic is taken from the terms carbonyl and hydroxyl, the two structures that make up the carboxyl group.

3. Properties of Carboxylic Acids • Very polar compounds • Can hydrogen bond to one another and to water • Boil at higher temperatures than aldehydes, ketones, or alcohols • Smaller carboxylic acids are soluble in water • Lower molecular weight acids have sharp, sour tastes and unpleasant aromas • Longer chain carboxylic acids are called fatty acids and are important components of biological membranes

4. Naming Carboxylic Acids - IUPAC • Determine the name of the parent compound, the longest continuous chain containing the carboxyl group. • Replace the –e ending with the suffix –oic acid. If there are two carboxyl groups, the suffix is –dioic acid. • Number the chain so the carboxyl carbon is number 1. • Name and number substituents.

5. Naming carboxylic acids of cycloalkanes • Add the suffix carboxylic acid to the name of the cycloalkane or substituted cycloalkane. • The carboxyl group is always numbered 1. • Other substituents are named and numbered as usual. Cyclopentanecarboxylic acid

6. Name the following.

7. Name the following. 2,4-dimethylpentanoic acid 2-ethylcyclopentanecarboxylic acid 3-methylcyclohexanecarboxylic acid 2,4-dichlorobutanoic acid

8. Common Carboxylic Acids

9. Draw structures for the following. • 2,3-dihydroxybutanoic acid • 2-bromo-3-chloro-4-methylhexanoic acid • 1,4-cyclohexanedicarboxylic acid • 4-hydroxycyclohexanecarboxylic acid • Formic acid • Acetic acid

10. Naming Aromatic Carboxylic Acids • These are usually named as derivatives of benzoic acid. • Generally, the –oic acid or –ic acid suffix is attached to the appropriate prefix. o-bromobenzoic acid

11. Naming Aromatic Carboxylic Acids • Often, the phenyl group is treated as a substituent. 2-phenylethanoic acid 4-phenylpentanoic acid

12. Draw structures for the following. • 2,4,6-tribromobenzoic acid • 2,2,2-triphenylethanoic acid • 3-phenylhexanoic acid • 3-phenylcyclohexanecarboxylic acid

13. Preparation of Carboxylic Acids • As discussed in Ch 14, carboxylic acids can be prepared from the oxidation of primary alcohols and/or aldehydes. 1º alcohol  Aldehyde  Carboxylic acid Examples: • 1-propanol • 2-methylbutanal

14. Carboxylic acid - ACID • Carboxylic acids act as acids because they are proton (H+) donors. They are weak acids that dissociate to form a carboxylate ion and a hydrogen ion as shown: carboxylic acid carboxylate anion hydrogen ion

15. Acid/Base Reaction • Since a carboxylic acid acts as an acid, it will neutralize a strong base like NaOH or KOH to form water and the salt of the carboxylic acid.

16. Examples Write a balanced equation and name the products that are formed. Acetic acid + sodium hydroxide  Benzoic acid + potassium hydroxide 

17. YOU TRY THESE! • Propanoic acid + potassium hydroxide  • Ethanol • Butanedial • Hexanoic acid + sodium hydroxide 

18. Structure of Esters • Esters are carboxylic acid derivatives. • They are formed from the reaction of a carboxylic acid with an alcohol.

19. Formation of an Ester H+, heat Carboxylic acid alcohol Ester Water EXAMPLE H+, heat Ethanoic acid ethanol (Acetic Acid) Ethyl ethanoate (Ethyl acetate)

20. Properties of Esters • Mildly polar • Have pleasant aromas • Found in natural foodstuffs (banana oil, pineapples, raspberries, etc.) • Boil at approximately the same temperature as aldehydes or ketones of similar molecular weights • Simpler ones are somewhat soluble in water

21. Naming Esters • Use the alkyl portion of the alcohol as the first name. • Remove the –ic acid ending of the carboxylic acid and replace it with –ate. • The same naming rules apply if the common name of the carboxylic acid is used.

22. Examples of Ester Names Methyl ethanoate (methyl acetate) Propyl ethanoate (propyl acetate) Methyl benzoate Methyl m-bromobenzoate

23. You Try These!

24. Answers to You Try These! • Cyclopentyl ethanoate • (cyclopentyl acetate) • Ethyl cyclohexanecarboxylate • Methyl p-nitrobenzoate • Methyl butanoate

25. Formation of Soap - Esterification • Fats and oils are triesters of the alcohol glycerol.

26. Formation of Soap - Saponification • When they are hydrolyzed by saponification, the products are soaps.

27. Acid Chlorides IUPAC name - Replace the –oic acid ending of the IUPAC name with –oyl chloride. Common name – Replace the –ic acid ending of the common name with –yl chloride.

28. Examples of Acid Chlorides Ethanoyl chloride (acetyl chloride) 3-bromopropanoyl chloride p-chlorobenzoyl chloride (4-chlorobenzoyl chloride)

29. Properties of Acid Chlorides • Noxious, irritating chemicals • Slightly polar • Boil at approximately the same temperature as aldehydes or ketones of similar molecular weights • React violently with water

30. Formation of Acid Chlorides Carboxylic acid Acid Chloride Ethanoic acid Ethanoyl chloride (acetic acid) (acetyl chloride)

31. Hydrolysis of Acid Chlorides Acid chloride water Carboxylic acid Hydrochloric acid Ethanoyl chloride ethanoic acid (acetyl chloride) (acetic acid)

32. Acid Anhydrides An acid anhydride is two carboxylic acids with a water molecule removed. “Anhydride” means without water.

33. Formation of Acid Anhydrides Carboxylic acid Carboxylic acid Water Acid anhydride