1. Carboxylic Acids and Esters Chapter 24
Hein * Best * Pattison * Arena
Colleen Kelley Chemistry Department Pima Community College
© John Wiley and Sons, Inc.
Version 1.0

2. Chapter Outline 24.1 Carboxylic Acids
24.4 Classification of Carboxylic Acids
24.2 Nomenclature and Sources of Aliphatic Carboxylic Acids
24.5 Preparation of Carboxylic Acids
24.3 Physical Properties of Carboxylic Acids

3. Chapter Outline (continued)
24.6 Chemical Properties of Carboxylic Acids
24.7 Nomenclature of Esters
24.8 Occurrence and Physical Properties of Esters
24. 9 Polyesters: Condensation Polymers
24.10 Chemical Properties of Esters
24.11 Glycerol Esters
24.12 Soaps and Synthetic Detergents
24.13 Esters and Anhydrides of Phosphoric Acid

4. Carboxylic Acids

5. The functional group of the carboxylic acid is called a carboxyl group and is represented in the following ways:

6. Nomenclature and Sources of Aliphatic Carboxylic Acids

7. IUPAC Rules for Naming Carboxylic Acids
To establish the parent name, identify the longest carbon chain that includes the carboxyl group.
Drop the final –e from the corresponding hydrocarbon name.
Add the suffix –oic acid.
HCOOH, methanoic acid
CH3COOH ethanoic acid
CH3CH2COOH propanoic acid

8. Naming Carboxylic Acids
Other groups bonded to the parent chain are numbered and named as we have done previously.

10. Nomenclature of Carboxylic Acids
Use of Greek letters:

11. Physical Properties of Carboxylic Acids

12. Physical Properties of Carboxylic Acids
Each aliphatic carboxylic acid molecule is polar and consists of a carboxylic acid group and a hydrocarbon group (-R).
Carbons 1-4 = water soluble
Carbons 5-8 = slightly water soluble
Carbons 8 and above = virtually insoluble in water

13. Physical Properties of Carboxylic Acids
The comparatively high boiling points for carboxylic acids are due to intermolecular attractions resulting from hydrogen bonding.

14. Physical Properties of Carboxylic Acids
Carboxylic acids are generally weak acids; that is, they are only slightly ionized in water.

15. Classification of Carboxylic Acids

16. Classification of Carboxylic Acids
saturated monocarboxylic acids
unsaturated carboxylic acids
aromatic carboxylic acids
dicarboxylic acids
hydroxy acids
amino acids

17. Unsaturated Carboxylic Acids
An unsaturated acid contains one or more C=C.
Acrylic acid, CH2=CHCOOH, also called propenoic acid.
Even one C=C bond exerts an influence on the physical and chemical properties of the acid.
Ex: stearic acid CH3(CH2)16COOH, mp = 70 C vs.
oleic acid CH3(CH2)7CH=CH(CH2)7COOH, mp = 16 C

18. Aromatic Carboxylic Acids
In an aromatic carboxylic acid, the carbon of the carboxyl group (-COOH) is bonded directly to a carbon in an aromatic ring.

20. Hydroxy Acids
Hydroxy acids have the functional group of an alcohol and a carboxylic acid.

21. Amino Acids
Each amino acid molecule has a carboxyl group that acts as an acid and an amino group that acts as a base.
About 20 biologically important amino acids, each with a different group represented by R, are found in nature.

22. Preparation of Carboxylic Acids

23. Preparation of Carboxylic Acids
oxidation of an aldehyde or primary alcohol
oxidation of alkyl groups attached to aromatic rings
hydrolysis of nitriles

24. Oxidation of an Aldehyde or a Primary Alcohol

25. Oxidation of Alkyl Groups Attached to Aromatic Rings

26. Hydrolysis of Nitriles
RCN + 2 H2O  RCOOH + NH4+

27. Chemical Properties of Carboxylic Acids

28. Chemical Properties of Carboxylic Acids
Acid-Base reactions
Substitution reactions
acid chlorides
acid anhydrides
esters
amides

29. Acid-Base Reactions
Because of their ability to form hydrogen ions in solution, acids in general have the following properties:
Sour taste
Change blue litmus to red and affect other suitable indicators.
Form water solutions with pH values less than 7.
Undergo neutralization reactions with bases for form water and a salt.

30. Acidity of Carboxylic Acids

31. Substitution Reactions
acid chlorides
acid anhydrides
esters
amides

32. Acid Chloride Formation
Thionyl chloride (SOCl2) reacts with carboxylic acids to form acid chlorides.

33. Acid Anhydride Formation
An organic anhydride is formed by the elimination of water from two molecules of carboxylic acid.

34. Ester Formation
An ester is formed by the reaction of an acid with an alcohol or a phenol; water is also produced in the reaction:

35. Nomenclature of Esters

36. Nomenclature of Esters
The alcohol part is named first, followed by the name of the acid modified to end in –ate.

38. Occurrence and Physical Properties of Esters

39. Properties of Esters
Simple esters derived from monocarboxylic acids and monohydroxy alcohols are colorless, generally nonpolar liquids or solids.
Low- and intermediate-molar-mass esters (both acids and alcohols up to about 10 carbons) are liquid with characteristic (usually fragrant or fruity) odors.

40. Occurrence and Properties of Esters
High-molar-mass esters (formed from acids or alcohols of 16 or more carbons) are waxes and are obtained from various plants.
They are used in furniture wax and automobile wax preparations.
Carnauba wax contains esters of 24-and 28-carbon fatty acids and 32- and 34-carbon alcohols.

41. Polyesters: Condensation Polymers

42. Polyesters: Condensation Polymers
Condensation polymers are formed by substitution reactions between neighboring monomers.
The polyesters are joined by ester linkages between carboxylic acid and alcohol groups.
The macromolecule formed may be linear or cross-linked.

43. Polyesters: Condensation Polymers

44. Chemical Properties of Esters

45. Hydrolysis
The most important reaction of esters is hydrolysis – the splitting of molecules through the addition of water.
A catalyst is often required.
An acid or base
In living systems, enzymes act as catalysts.

46. Acid Hydrolysis
The hydrolysis of an ester involves the reaction with water to form a carboxylic acid and an alcohol.

47. Alkaline Hydrolysis (Saponification)
Saponification is the hydrolysis of an ester by a strong base (NaOH or KOH) to produce an alcohol and a salt (or soap if the salt formed is from a high-molar-mass acid).
Notice that in saponification, the base is a reactant and not a catalyst.

48. Glycerol Esters

49. Fats and Oils
Fats and oils are esters of glycerol and predominantly long-chain fatty acids.
Fats and oils are also called triacylglycerols or triglycerides, since each molecule is derived from one molecule of glycerol and three molecules of fatty acid:

51. Triacylglycerol
The structural formulas of triacylglycerol molecules differ because:
The length of the fatty acid chain varies from 4 to 20 carbons, but the number of carbon atoms in the chain is nearly always even.
Each fatty acid may be saturated or unsaturated and may contain one, two, or three C=C.
A triacylglycerol may, and frequently does, contain three different fatty acids.

53. The most abundant unsaturated acids in fats and oils contain 18 carbon atoms.
In all of these naturally occurring unsaturated acids, the configuration about C=C is cis.

54. Physical Differences Between Fats & Oils
Fats are solid; oils are liquid at room temperature
Fats contain a larger portion of saturated fatty acids whereas oils contain greater amounts of unsaturated fatty acids.
Polyunsaturated means that each molecule of fat contains several C=C.

55. Comparison of Fats & Oils
Fats come from animal sources:
Lard from hogs, tallow from cattle and sheep
Oils come from vegetable sources:
Olives, corn, peanut, soybean, canola

56. Hydrogenation of Glycerides
Hydrogen adds to the C=C of oil to saturate it and form fats:
H2 + -CH=CH-  -CH2-CH2-
In practice, only some of the C=C are allowed to become saturated.
Partial hydrogenation Ni

57. Hydrogenolysis
Triacylglycerols can be split and reduced in a reaction called hydrogenolysis (splitting by hydrogen).

58. Hydrolysis
Triacylglycerols can be hydrolyzed, yielding fatty acids and glycerol.

59. Saponification
The saponification of a fat or oil involves the alkaline hydrolysis of a triester.
The products formed are glycerol and the alkali metal salts of fatty acids, which are called soaps.

60. Soaps and Synthetic Detergents

61. Soaps and Synthetic Detergents
In the broadest sense possible, a detergent is simply a cleansing agent.
A soap is distinguished from a synthetic detergent on the basis of chemical composition and not on the basis of function or usage.

62. Soaps Salts of long-chained fatty acids are called soaps.
Fat or oil + NaOH  Soap + Glycerol

63. Figure 24. 1 Cleansing action of soap.

64. Synthetic Detergents - Anionic
The one great advantage these synthetic detergents have over soap is that their Ca+2, Mg+2, and Fe+3 salts, as well as their Na+1 salts, are soluble in water. Therefore, they are nearly as effective in hard water as in soft water.

65. Synthetic Detergents – Nonionic
The molecule of a nonionic detergent contains a grease-soluble component and a water soluble component.
Some of these substances are especially useful in automatic washing machines because they have good detergent, but low sudsing, properties.

66. Biodegradability
Organic substances that are readily decomposed by microorganisms in the environment are said to be biodegradable.
Detergents that contain straight-chain alkyl groups are biodegradable.

68. Esters and Anhydrides of Phosphoric Acid

69. Phosphoric Acid
Phosphoric acid has a Lewis structure similar to that of a carboxylic acid.
Phosphoric acid reacts with an alcohol to form a phosphate ester.

70. The End