1. 1

2. 2 Carboxylic Acids

3. 3 A poem by Ogden Nash The ant has made himself illustrious Through constant industry industrious So what? Would you be calm and placid If you were full of formic acid?

4. 4 The functional group of the carboxylic acid is called a carboxyl group and is represented in the following ways:

5. 5 Nomenclature and Sources of Aliphatic Carboxylic Acids

6. 6 IUPAC Rules for Naming Carboxylic Acids 1.To establish the parent name, identify the longest carbon chain that includes the carboxyl group. 2.Drop the final –e from the corresponding hydrocarbon name. 3.Add the suffix –oic acid. HCOOH, methanoic acid CH 3 COOH ethanoic acid CH 3 CH 2 COOH propanoic acid

7. 7 Naming Carboxylic Acids Other groups bonded to the parent chain are numbered and named as we have done previously.

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9. 9 Common Names for Acids HCOOHFormicFormica (ant) CH 3 COOHAceticAcetum (sour) CH 3 CH 2 COOHPropionicPro (first) + Pion (fat) CH 3 (CH 2 ) 2 COOHButyricButyrum (butter) CH 3 (CH 2 ) 3 COOHValericValere (strong) CH 3 (CH 2 ) 4 COOHCaproicCaper (goat)

10. 10 Common Names for Acids CH 3 (CH 2 ) 6 COOHCaprylicCaper (goat) CH 3 (CH 2 ) 8 COOHCapric Caper (goat) CH 3 (CH 2 ) 10 COOHLauricLaurel CH 3 (CH 2 ) 12 COOHMyristicMuron (perfume) CH 3 (CH 2 ) 14 COOHPalmiticPalm Oil CH 3 (CH 2 ) 16 COOHStearicStear (solid fat)

11. 11 Nomenclature of Carboxylic Acids Use of Greek letters:

12. 12 Physical Properties of Carboxylic Acids

13. 13 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

14. 14 Physical Properties of Carboxylic Acids The comparatively high boiling points for carboxylic acids are due to intermolecular attractions resulting from hydrogen bonding.

15. 15 Physical Properties of Carboxylic Acids Carboxylic acids are generally weak acids; that is, they are only slightly ionized in water.

16. 16 Classification of Carboxylic Acids

17. 17 Types of Carboxylic Acids There are five major types of carboxylic acids in addition to the saturated monocarboxylic acids like acetic acid (CH 3 COOH ). These acids are summarized and discussed in this section.

18. 18 Types of Carboxylic Acids

19. 19 Unsaturated Carboxylic Acids An unsaturated acid contains one or more C=C. –Acrylic acid, CH 2 =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 CH 3 (CH 2 ) 16 COOH, mp = 70 ºC vs. oleic acid CH 3 (CH 2 ) 7 CH=CH(CH 2 ) 7 COOH, mp = 16 ºC

20. 20 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.

21. 21 Dicarboxylic Acids Dicarboxylic acids have two carboxyl (COOH) groups. These acids undergo a decarboxylation reaction ( i.e.loss of CO 2 ) to form a monocarboxylic acid or an anhydride as shown below.

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23. 23 Citric acid is a hydroxytricarboxylic acid. It is 5-8% of lemon juice and widely distributed in plant and animal tissues. It is also an important acid in the citric acid cycle. Examples of other dicarboxylic acids are listed in Table 24.2.

24. 24 Hydroxy Acids Hydroxy acids have the functional group of an alcohol and a carboxylic acid.

25. 25 Hydroxy Acids Malic acid and tartaric acid are two other common  -hydroxy acids found in apples and grapes respectively.

26. 26 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. The R group does not necessarily represent an alkyl group in amino acids.

27. 27 Preparation of Carboxylic Acids

28. 28 Preparation of Carboxylic Acids oxidation of an aldehyde or primary alcohol oxidation of alkyl groups attached to aromatic rings hydrolysis of nitriles

29. 29 Oxidation of an Aldehyde or a Primary Alcohol

30. 30 Oxidation of Alkyl Groups Attached to an Aromatic Ring Alkyl benzenes are oxidized in basic solution to the carboxylate salt and then protonated with acid to form benzoic acid.

31. 31 Hydrolysis of Nitriles RCN + 2 H 2 O  RCOOH + NH 4 + H+H+

32. 32 Chemical Properties of Carboxylic Acids

33. 33 Chemical Properties of Carboxylic Acids 1.Acid-Base reactions 2.Substitution reactions acid chlorides acid anhydrides esters amides

34. 34 Acid-Base Reactions Because of their ability to form hydrogen ions in solution, acids in general have the following properties: 1.Sour taste 2.Change blue litmus to red and affect other suitable indicators. 3.Form water solutions with pH values less than 7. 4.Undergo neutralization reactions with bases for form water and a salt.

35. 35 Acidity of Carboxylic Acids

36. 36 Substitution Reactions acid chlorides acid anhydrides esters amides

37. 37 Acid Chloride Formation Acid chlorides are prepared by reacting thionyl chloride (SOCl 2 ) and a carboxylic acid.

38. 38 Reactivity of Acid Chlorides Acid chlorides are very reactive and will hydrolyze back to the carboxylic acid if exposed to moisture.

39. 39 Acid Anhydride Formation An organic anhydride is formed by the elimination of water from two molecules of carboxylic acid.

40. 40 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:

41. 41 Nomenclature of Esters

42. 42 Nomenclature of Esters The alcohol part is named first, followed by the name of the acid modified to end in –ate.

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44. 44 Occurrence and Physical Properties of Esters

45. 45 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.

46. 46 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.

47. 47 Chemical Properties of Esters

48. 48 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.

49. 49 Acid Hydrolysis The hydrolysis of an ester involves the reaction with water to form a carboxylic acid and an alcohol.

50. 50 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.

51. 51 Glycerol Esters

52. 52 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:

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54. 54 Triacylglycerol The structural formulas of triacylglycerol molecules differ because: 1.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. 2.Each fatty acid may be saturated or unsaturated and may contain one, two, or three C=C. 3.A triacylglycerol may, and frequently does, contain three different fatty acids.

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56. 56 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.

57. 57 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.

58. 58 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

59. 59 Hydrogenation of Glycerides Hydrogen adds to the C=C of oil to saturate it and form fats: H 2 + -CH=CH-  -CH 2 -CH 2 - In practice, only some of the C=C are allowed to become saturated. –Partial hydrogenation Ni

60. 60 Hydrogenolysis Triacylglycerols can be split and reduced in a reaction called hydrogenolysis (splitting by hydrogen).

61. 61 Hydrolysis Triacylglycerols can be hydrolyzed, yielding fatty acids and glycerol.

62. 62 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.

63. 63 Soaps and Synthetic Detergents

64. 64 Soaps and Synthetic Detergents In the broadest sense possible, a detergent is simply a cleansing agent. A soap is distinguished from a synthetic detergent (syndet) on the basis of chemical composition and not on the basis of function or usage.

65. 65 Soaps Salts of long-chained fatty acids are called soaps. Fat or oil + NaOH  Soap + Glycerol

66. 66 Cleansing action of soap.

67. 67 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.

68. 68 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.

69. 69 Biodegradability Biodegradable organic substances are those that can be readily decomposed by microorganisms in the environment. For example detergents with straight-chain alkyl benzenes are biodegradable.

70. 70 Biodegradability However detergents with branched-chain alkyl benzenes are not biodegradable.

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