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Home , Alkyl, Carboxylate, Carboxylic acid, Derivative (chemistry), Thiocarboxylic acid

Chapter 5 Carboxylic and

Carboxylic Acids • Carboxylic acids are weak organic acids which Chapter 5 contain the carboxyl group (RCO2H): Carboxylic Acids and Esters O

C O H O RCOOH RCO2H Chapter Objectives: O condensed ways of • Learn to recognize the carboxylic , , and related functional groups. RCOH writing the carboxyl • Learn the IUPAC system for naming carboxylic acids and esters. group a C H • Learn the important physical properties of the carboxylic acids and esters. • Learn the major of carboxylic acids and esters, and learn how to O predict the products of ester synthesis and reactions. the carboxyl group • Learn some of the important properties of condensation , especially the .

Mr. Kevin A. Boudreaux • The tart flavor of sour-tasting foods is often caused Angelo State University CHEM 2353 Fundamentals of Organic by the presence of carboxylic acids. Organic and for Today (Seager & Slabaugh) www.angelo.edu/faculty/kboudrea 2

Nomenclature of Carboxylic Acids • Select the longest chain containing the carboxyl group. The -e ending of the parent name is replaced by the suffix -oic acid. • The carboxyl carbon is always numbered “1” but the number is not included in the name. • Name the attached to the chain in the Nomenclature of usual way.

• Aromatic carboxylic acids (i.e., with a CO2H Carboxylic Acids directly connected to a ring) are named after the parent compound, . O

C OH

3 4 Benzoic acid

Examples: Naming Carboxylic Acids Examples: Naming Carboxylic Acids • Name the following compounds: • Name the following compounds:

O O O Br O HCOH CH3 COH COH CH3CHCH2 COH CH3CH2CHCH3

O O

HO CCH2CH2CH3 CH3CH2 COH CH3 O

CH3CHCH2 COH

CH2CH2CH3

5 6 Chapter 5 Carboxylic Acids and Esters

Examples: Naming Carboxylic Acids Examples: Naming Carboxylic Acids • Name the following compounds: • Name the following compounds: CH 3 CO H O 2 O CH O COH 3 COH CH C OH CH3CCH3 CH3 O Cl CH2CH2CHCH3 CH3 C OH

7 CH3CHCH3 8

More Complicated Acids Examples: Drawing Carboxylic Acids • For molecules with two carboxylic acid groups the • Draw structural formulas for the following molecules: carbon chain in between the two carboxyl groups – 2-methylpropanoic acid (including the carboxyl ) is used as the longest chain; the suffix -dioic acid is used. • For molecules with more than two carboxylic acid groups, the carboxyl groups are named as carboxylic – 2,2,5-trimethylhexanoic acid acid substituents. O O O O HOC C OH – 4,5-dimethyl-3-nitrooctanoic acid ethanedioic acid HO C CH2 CH CH2 C OH

O O C OOH HO C CH2 C OH propane-1,2,3-tricarboxylic acid propanedioic acid 9 10

Examples: Drawing Carboxylic Acids • Draw structural formulas for the following molecules: – para-bromobenzoic acid

– 2,4,6-trinitrobenzoic acid

– 4-ethylpentanedioic acid (what’s wrong with this name?)

11 12 Chapter 5 Carboxylic Acids and Esters

Physical Properties of Carboxylic Acids • Carboxylic acids bond to themselves to form a dimer: O H O

RC C R Physical Properties of O H O • Carboxylic acids also form hydrogen bonds to Carboxylic Acids water molecules: H H O O

RC H O H O 13 14 H

Physical Properties of Carboxylic Acids Physical Properties of Carboxylic Acids • Since carboxylic acids can form more than one set of • As the number of carbons in a carboxylic acid series hydrogen bonds, their boiling points are usually becomes greater, the increases and the higher than those of other molecules of the same in water decreases. molecular weight (MW). • Many carboxylic acids that are liquids at room • Low-MW carboxylic acids are generally liquids at temperature have characteristically sharp or room temp. (often, they are somewhat oily); higher- unpleasant odors. MW carboxylic acids are generally waxy solids. – Ethanoic acid/ is the main ingredient in • Carboxylic acids with 12 to 20 carbon are . often referred to as fatty acids, since they are found in the in and oils (more later). – Butanoic acid is partially responsible for the odor of locker rooms and unwashed socks. • Short-chain carboxylic acids are also generally more soluble in water than compounds of similar MW, – Hexanoic acid is responsible for the odor of since they can to more than one Limburger cheese. water molecule. • Like most acids, carboxylic acids tend to have a sour

15 taste (e.g., vinegar, , etc.) 16

Table 5.2 Physical properties of some carboxylic acids Boiling Points of Various Functional Groups Common Structural BP MP Solubility Name Formula (°C) (°C) (g/100 mL H2O)

Formic acid H—CO2H 101 8 Infinite

Acetic acid CH3—CO2H 118 17 Infinite CH3CH2—CO2H 141 -21 Infinite

Butyric acid CH3(CH2)2—CO2H 164 -5 Infinite

Valeric acid CH3(CH2)3—CO2H 186 -34 5

Caproic acid CH3(CH2)4—CO2H 205 -3 1

Caprylic acid CH3(CH2)6—CO2H 239 17 Insoluble CH (CH ) —CO H 270 32 Insoluble Figure 5.4 3 2 8 2 The boiling points of CH3(CH2)10—CO2H 299 44 Insoluble carboxylic acids compared CH3(CH2)12—CO2H Dec. 58 Insoluble to 1° , CH (CH ) —CO H Dec. 63 Insoluble and , and 3 2 14 2 . CH3(CH2)16—CO2H Dec. 71 Insoluble 17 18 Chapter 5 Carboxylic Acids and Esters

Comparing Physical Properties Examples: Predicting Physical Properties Boiling Point: Water Solubility: • Arrange the following compounds in order of Carboxylic acid increasing boiling point. (All of the compounds Carboxylic acid have about the same molecular weight.) Alcohols Alcohols Aldehydes/Ketones Aldehydes/Ketones – 1-pentanol Ethers Ethers – hexane Alkanes Alkanes – butanoic acid – pentanal Name Molecular Boiling Solubility in water weight point • Which member of each of the following pairs of 72 g/mol 35°C Insoluble compounds would you expect to have a higher Diethyl 74 g/mol 35°C Insoluble solubility in water?

Butanal 72 g/mol 76°C 7.1 g / 100 mL H2O – 2-butanone or propanoic acid

1-Butanol 74 g/mol 118°C 9.1 g / 100 mL H2O – hexanoic acid or ethanoic acid Propanoic acid 74 g/mol 141°C Infinite 19 20

Important Carboxylic Acids O O O

CH3CH2 C OH HOHC CH3 C OH Propanoic acid Methanoic acid Ethanoic acid (Propionic acid) () (Acetic acid) Found in Swiss cheese; (from Latin formica, ant) (from Latin acetum, vinegar) salts of this acid are used A component of the venom Vinegar is a 5% solution of as mold inhibitors of ants and caterpillars; acetic acid dissolved in water; produced in the body when acetic acid is also responsible methanol is consumed for the taste of sour wine (from Some Important the oxidation of ) and sourdough bread Carboxylic Acids O O CH3CH2CH2 C OH CH3CH2CH2CH2CH2 C OH Butanoic acid Hexanoic acid () () (from Latin butyrum, ) Responsible for the odor of This acid has a foul, rancid odor; Limburger cheese. produced from the breakdown of soft triglycerides in butter

21 22

O O OH O O OH HO HO OH OH O O OH H N 2 An alpha-hydroxy acid used in OH 2-hydroxy-1,2,3-propanetricarboxylic acid cosmetics and skin creams; para-Aminobenzoic aid (PABA) OH (Citric acid) Used in sunscreens; absorbs alpha-hydroxy acids are thought to Found in citrus fruits (lemons, grapefruit, short-wavelength UV light. It is also required loosen the cells of the epidermis and 2-hydroxypropanoic acid oranges, etc.); commonly used in buffering by bacteria for the production of folic acid, accelerate the flaking off of dead skin; () solutions with citrate needed to maintain the growth of healthy cell however these compounds can increase Produced from the of sugars walls; sulfa drugs block the uptake of PABA the skin's sensitivity to UV light under anaerobic conditions; found in sweat, by bacteria, causing them to be unable to sour milk, fermented pickles, sauerkraut, manufacture folic acid, and thus preventing and yogurt; produced in muscles from O O under anaerobic conditions (the the bacteria from multiplying O buildup of lactic acid leads to a heavy, weak feeling, and muscle cramps); produced after O O HO HO OH OH death during the breakdown of sugars in the body by bacteria, inactivating the Found in many leafy green plants O OH that allow the transport of , HO OH such as rhubarb and spinach; causing rigor mortis combines with calcium ions in the Responsible for the sharp body to produce insoluble salts, A white, crystalline solid; used in taste of apples (genus Malus) which form kidney stones the manufacture of some polyesters 23 24 Chapter 5 Carboxylic Acids and Esters

O OH O O HO H2N OH OH OH O OH Gamma-aminobutanoic acid (GABA) N A inhibitory neurotransmitter; ethanol binds to the same as GABA at a neighboring location, distorting the A water-soluble, B-Complex vitamin obtained Found naturally in wine, and is protein so that GABA binds more easily, further inhibiting the from fish, green vegetables, lean meat, poultry, responsible for some of the sharp taste of cell from firing; benzodiazepines such as Valium also bind to whole-grain and enriched bread and cereal; wine; it is added to many sour-tasting the same protein but at a different site, inhibiting the cell still produced in the body from ; sweet foods. The potassium , cream further, and sometimes with deadly consequences essential for growth, healthy tissues, the of tartar, has many cooking applications; production of energy from carbohydrates, and the potassium-sodium salt, Rochelle salt, the production of fats is a mild laxative. O O OO

O O HO N OH HO O- Na+ HO HO OH H NH2 OH OH Monosodium Glutamate (MSG) Pantothenic acid O O The sodium salt of the glutamate; A water-soluble B-complex vitamin; produced in meat during the decomposition of converted by the body into ; with inosine monophosphate (IMP), one Occurs naturally in many plants, and is essential for An intermediate along the , which helps the body of the major substances responsible for the flavor vegetable and animal tissue respiration; used in baking produce energy from food of meat; MSG is also added to some foods to powders, and in some fruit drinks as a replacement for enhance their meaty flavor citric acid 25 26

Acids and Bases • Acids: – have a sour taste.

– react with active metals to produce H2 gas. – turn blue litmus red. Chemical Properties of • Bases: – have a bitter taste and a slippery feel. Carboxylic Acids – turn red litmus blue. • When they react with each other, acids and bases cancel each others properties in a neutralization reaction: acid +  salt + water

27 28

Acids The pH Scale •An acid gives a proton (H+) to another species. • The acidity of a solution is measured + Acids produce hydronium ions, H3O , when they using the pH scale. The pH of a are dissolved in water: solution is defined as – + + H—A + H2O  A + H3O pH = - log[H3O ] •A strong acid is one that completely dissociates in water (i.e., every molecule of the acid splits apart): + - Acidic: pH < 7.00 [H3O ] > [OH ] – + H—Cl + H2O  Cl + H3O + - Basic: pH > 7.00 [H3O ] < [OH ] •A weak acid is one in which only a small percentage of the molecules are dissociated at any Neutral: pH = 7.00 [H O+] = [OH-] one time (in other words, there is also a backwards 3 reaction, where the acid molecule is regenerated): – + H—F + H2O h F + H3O 29 30 Chapter 5 Carboxylic Acids and Esters

The Acidity of Carboxylic Acids The Acidity of Carboxylic Acids • Carboxylic acids are weak acids; in water, they • The of a carboxylic acid is a reversible dissociate to produce hydronium ions and reaction, and the position of the equilibrium can be ions: affected by the addition of acid (low pH) or by adding base (high pH): O O O base O RCOH+ H2O RCO + H3O (high pH) carboxylic acid carboxylate RC + H2O RC+ H3O acid O H (low pH) O • A 1.0 M solution of acetic acid is about 0.5% dissociated into hydronium and ions: carboxylic acid carboxylate ion O O •Atthephysiological pH of 7.4 (the pH of most body CH3 COH+ H2O CH3 CO + H3O fluids) the carboxylate form of most carboxylic acids acetic acid acetate ion is the predominate form.

31 32

Carboxylate Salts • Carboxylic acids react with strong bases such as sodium (NaOH) and potassium hydroxide (KOH) to produce carboxylate salts. • Carboxylate salts are named by naming the metal first, and changing the -ic acid ending of the carboxylic acid name to -ate. O O

Carboxylate Salts - + RCOH+NaOH RCONa + H2O carboxylic acid base metal carboxylate

O O

- + - + CH3 CO Na CH3CH2CH2CH2 CO NH4 sodium ethanoate 33 () 34

Examples: Carboxylate Salts Examples: Carboxylate Salts • Draw the structure of pyruvate, the form of pyruvic • Complete the following reactions and name the acid which is found as an intermediate in energy carboxylate salt products. conversion reactions in living organisms. O O O C CH3 CCOH OH + NaOH

• Complete the following reactions and name the carboxylate salt products. O O C CH3 COHNaOH+ OH + KOH O CH3 CH3

HOC CH2CHCH3 + NaOH 35 36 Chapter 5 Carboxylic Acids and Esters

Physical Properties of Carboxylate Salts Important Carboxylate Salts • Carboxylate salts are ionic compounds, and are O O O OH O typically solids at room temperature. O- Na+ O- Na+ +Na -O O- Na+ Sodium propanoate O O- Na+ • Because they contain charges, carboxylate salts are O Sodium citrate Sodium benzoate The sodium salt of citric acid, sodium citrate, is Found in cranberries and typically much more soluble in water than the O- Ca2+ used in buffers with citric acid to maintain prunes; commonly used desirable characteristics of foams and gels (jelly, 2 carboxylic acids from which they are derived. as a preservative in ice cream, candy, whipped cream, etc.) by Calcium propanoate baked goods, ketchup, controlling the pH of the product; also used in carbonated beverages, Commonly used medicines and blood for transfusions; also – This is important in the formation of (more etc. preservatives; found functions as an anticoagulant in blood in bread, cakes, and later). cheeses

CH3 O O C2H5 + OO N -O N C2H5 CH H - + O 3 CH3(CH2)16COHNaOH+ CH3(CH2)16CO Na + H2O Denatonium benzoate ('Bitrex') Benzyl diethyl ((2,6-xylylcarbamoyl)methyl) Stearic acid Sodium stearate O- Zn2+ Zinc 10-undecylenate 2 benzoate (octadecanoic acid) (sodium octadecanoate) Used to treat athlete's foot (Desenex) Discovered in 1958, this is the bitterest-tasting compound known; as little as ten parts per million make substances insoluble in water soluble in water unbearably bitter to most humans. It is used as an aversive found in beef and agent, an additive that prevents accidental ingestion of a toxic substance. It is used to denature ethanol, methanol, some and rubbing , and well as , paints, arnishes, 37 antifreeze, etc. 38

Esters •An ester (“carboxylic ester” in the textbook) is a derivative of a carboxylic acid in which there is a carbon group connected to the single-bonded :

O O Esters RCOR' RCOC ester linkage carbon group

39 40

Nomenclature of Esters Examples: Ester Nomenclature O • Name the following compounds: CH O RCOR' 3 O

CH3 CH C O CH3 HCOCH3 acid part alcohol part • Name the or aromatic portion contributed by the “alcohol part” first. • The “acid part” is named as a carboxylic acid, with the -ic acid suffix changed to -ate. OCH2CH3 O O CH3CH2 O C CH2CH2CHCH3

CH3 CO CH3 CH3CH2CH2 CO CH2CH3

41 42 Chapter 5 Carboxylic Acids and Esters

Examples: Ester Nomenclature Examples: Ester Nomenclature • Name the following compounds: • Name the following compounds:

O CH 3 O

CH3CH2CH C O CHCH3 CH3CH2CH2 CO

CH2CH3

CH3 O O CO CHCH 2 3 CO CH3

43 44

Examples: Drawing Esters Examples: Drawing Esters • Draw structural formulas for the following molecules: • Draw structural formulas for the following molecules: – methyl butanoate – propyl 2,2,3,4-tetramethylhexanoate

– ethyl 2-methylpropanoate – isopropyl benzoate

– methyl 2,4-dimethylhexanoate – methyl para-nitrobenzoate

45 46

Important Esters HO OH O

H OH O O O Amyl acetate OH Also known as banana oil and pear oil; the commercially available compound is a Vitamin C (ascorbic acid) mixture of amyl (pentyl) A water-soluble vitamin found in citrus fruits; prevents scurvy; essential for healthy blood vessels, bones, and teeth; helps O CH form , a protein that holds tissues 3 CH3 Some Important Esters together + O N O CH3 O O– Acetylcholine O N an important neurotransmitter

O Peroxyacetyl (PAN) O Produced by the action of sunlight on fragments of unburnt fuel, oxygen, and nitrogen dioxide; one of the O irritants (lachrymator) found in Benzyl acetate photochemical smog 47 oil of jasmine 48 Chapter 5 Carboxylic Acids and Esters

O Polymers with Ester Groups

OH O O O O O OO Geranyl acetate Coumarin geranium oil Found in lavender O O O Methyl (vinyl oil, sweet clover C and tonka beans acetate) OO O Methyl methacrylate N Polymerizes to form polyvinyl Warfarin acetate; used in acrylic paints Polymerizes to form A potent rodenticide Methyl cyanoacrylate poly(methyl methacrylate); CH3(CH2)14 O(CH2)15CH3 in combination with pigments O Polymerizes on contact with and a which causes trade names are Lucite, Spermaceti surfaces containing trace the to be suspended in Plexiglass, and Perspex; Also known as cetyl palmitate; found in amounts of water and an emulsion; also used in the bulky methyl and methyl ester groups cause the OCH3 the spermaceti organ or case above the alcohols to form Superglue; safety glass (a layer of PVA skull of the sperm whale (Physeter superglue is also used in sandwiched between two polymer to be oriented macrocephalus). Its exact function is not surgery in place of sutures, layers of glass) and chewing chaotically within the solid OH known but it may be used as and by morticians to seal gum polymer, allowing light to Methyl salicylate "cushioning," allowing the whale's head to the eyes and lips of their pass through without Also known as oil of wintergreen and betula be used as a battering ram in fights clients scattering, rendering the oil; used as a flavoring and as an ingredient between males (see Moby Dick), as a plastic transparent in deep heating rubs. It also fluoresces under regulator of the whale's buoyancy in Lauryl methacrylate ultraviolet light, producing visible blue light. water, or as an aid in echolocation in O Used to make the polymer poly(lauryl This is most apparent in Wint-O-Green focusing sound waves. Spermaceti was methacrylate); used as an additive in Lifesavers, which contain methyl salicylate highly sought by whalers in the 18th and O viscostatic engine oils, which keeps as their flavoring. It is also used in some 19th centuries, and was widely used the oild viscous at high temperatures. sunscreen lotions commercially. 49 50

Synthesis of Esters: Esterification Reactions • The simplest way to synthesize an ester is to heat a carboxylic acid with an alcohol or (plus an acid catalyst); the oxygen of the alcohol adds to the carboxyl group, splitting out a molecule of water in the process (an esterification reaction).

O O H+ Reactions of Esters C H + H O R' C R' + H O H  R O an alcohol R O a carboxylic or acid a phenol an ester

51 52

Synthesis of Esters: Esterification Reactions Synthesis of Esters: Esterification Reactions

• Since this reaction is a reversible reaction, it often O O reaches an equilibrium with a large amount of unreacted starting material still present. C + HO R' C R' + H Cl R Cl R O • Better yields are obtained using either acid acid chloride an alcohol an ester chlorides or acid anhydrides as starting materials. or These reactions are nonreversible. a phenol

O O O O O O O C C C R Cl C C ++HO R' C R' C H R O R R O R O R an alcohol R O acid chloride acid anhydride acid anhydride or an ester a carboxylic a phenol acid

53 54 Chapter 5 Carboxylic Acids and Esters

Examples: Esterification Reactions Examples: Esterification Reactions • Write both products of the following reactions: • Write both products of the following reactions:

O H+ O O CH3CH2CH2 C OH + CH3CH2OH CH3 C O CCH3 + CH3CH2OH

O OH

CH3 C Cl +

55 56

Examples: Esterification Reactions Examples: Esterification Reactions • Write both products of the following reactions: • Write both products of the following reactions:

O OH O

C O O CH3 C Cl + CH3 CH CH3 OH + CH3 C O CCH3 OH

57 58

Pain, Pain, Go Away More Pain Relievers

O O O O

HN CH3 OH OH OH O OH O O CH3 Found in the bark of the willow (acetylsalicylic acid) OH OH tree (Salix); a tea brewed from CH O the bark reduces fever and Produced by reacting salicylic acid with acetic Acetominophen 3 relives pain and inflammation, anhydride, giving a compound which is less Does not cause stomach Naproxen but is very acidic, and causes acidic, and does not cause as much irritation, irritation, and has Ibuprofen An analgesic, anti-pyretic, irritation of the mucous but still retains all of the beneficial medical analgesic and antipyretic An analgesic, antipyretic, and anti-inflammatory membranes in the mouth, throat, properties; aspirin seems to work by blocking properties that are similar and anti-inflammatory drug; active ingredient in and stomach, and can cause the production of prostaglandins, hormones to aspirin, but no drug; it is also not Aleve painful ulcers and stomach which may be responsible for producing pain, anti-inflammatory irritating to the stomach bleeding fever and inflammation; one of the most functions; available under lining; available under the commonly used pharmaceutical drugs; over 40 the trade names Tylenol, trade names Motrin, million pounds are produced in the United Excedrin Aspirin Free, Advil, Ibuprin, Nuprin, and States per year Panadol, and Anacin-3 Mediprin

59 60 Chapter 5 Carboxylic Acids and Esters

Condensation Polymers: Polyesters Condensation Polymers: Polyesters O O • Condensation polymers are polymers which form HOCH2CH2OH C C HOCH2CH2OH glycol HO OH Ethylene glycol with the loss of a small molecule (typically water or Terephthalic acid HCl).

O O • Condensation polymers, such as polyesters and C C (, Ch. 6), form when each of the HOCH2CH2O OCH2CH2OH monomers contain two of the same , so the reaction can take place at both ends. O O O O O O C C C C C C

HO OCH2CH2O OCH2CH2O OH

O O O O O O C C C C C C

HOCH2CH2O OCH2CH2O OCH2CH2O OCH2CH2OH

O O O O O O O O O O C C C C C C C C C C OH HO OCH2CH2O OCH2CH2O OCH2CH2O OCH2CH2O

61 etc. 62

Condensation Polymers: Polyesters Reactions of Esters: Ester Hydrolysis • Esters may be broken apart under acidic conditions O O by water (a hydrolysis reaction) to form a CC carboxylic acid and an alcohol.

H O O CH2CH2 OH n Polyethylene terephthalate (PET) OO A H+ H O Over 3 billion pounds of PET are made every year. It forms a RCOR'++2 RCOH R'OH very linear chain, and is very inert. It can be melted and pulled an ester a carboxylic acid an alcohol through spinnerettes to make fibers, threads, or yarn (Dacron, Fortrel, Terylene), where it can be used in automobile tire cord, permanent press clothing, sutures, replacements for damaged sections of blood vessels and the esophagus, etc. PET melts can • This is essentially the reverse reaction of the also be forced through narrow slits to produce thin sheets or synthesis of esters from carboxylic acids and ribbons known as Mylar; this form is used as the support alcohols. medium in audio and video tape.

63 64

Reactions of Esters: Examples: Splitting Esters • Esters may be broken apart under basic conditions (Because Breaking Up Is Hard To Do) by (lye) or potassium hydroxide • Complete the following reactions: to form carboxylate salts and alcohols. O H+ OO CH3 COCH2CH3 + H2O

RCOR'NaOH+ RCO- Na+ + R'OH an ester base a carboxylate salt an alcohol O

• This reaction is important in the production of CH3 COCH2CH3 + NaOH soaps.

65 66 Chapter 5 Carboxylic Acids and Esters

Triglycerides • Long-chain carboxylic acids, often referred to as fatty acids, are stored by living organisms by combining them with to produce tri-esters called triglycerides. • Triglycerides at room temperature are usually either solids or semi-solids (fats), or viscous liquids (oils). Triglycerides and Soaps O CH2 OH O CH2 OC(CH2)16CH3 O CH OH HO C(CH2)16CH3 CH OC(CH2)16CH3 stearic acid CH2 OH O (a ) glycerol CH2 OC(CH2)16CH3 glyceryl tristearate (tristearin) 67 68 a

Some Saturated Fatty Acids Some Saturated Fatty Acids O O OH Stearic acid OH A saturated fatty acid found in lard, beef fat, Palmitic acid butterfat, cottonseed oil; the sodium salt, produced A fatty acid, found in lard, beef fat, butterfat, and cottonseed oil; by heating lard with sodium hydroxide, can be used the triglycerides in cocoa butter have attached to the as a central oxygen, with stearic acid or palmitic acid on the other O ; this more regular composition gives cocoa butter a much sharper melting point than is usually observed in fats, and OH remains brittle almost up to its melting point of 34°C (just Lauric acid below body temperature); the sudden melting of chocolate in the Found in oil; mouth gives it a pleasant feeling of coolness commonly used in soaps O

OH Myristic acid A fatty acid found in butterfat, , and nutmeg oil O

OH 69 70 A fatty acid found in

Some Unsaturated Fatty Acids Some Unsaturated Fatty Acids O O

OH OH

Oleic acid An unsaturated fatty acid; the chain is much less flexible than that of stearic acid because of the double bond, and cannot pack as tightly, A omega-3 polyunsaturated fatty acid found in fish oil and seafoods; omega-3 fatty so the triglycerides it forms are oils and not fats; found in olive oil, acids may, according to some studies, help to lower the risk of heart disease cocoa butter and chocolate, beef fat, lard, and peanut oil O O

OH OH

Palmitoleic acid Linolenic acid An unsaturated fatty acid found in butterfat and cod liver oil A omega-6 polyunsaturated fatty acid found in linseed oil and corn oil O O

OH OH An omega-3 polyunsaturated fatty acid found in fish oil and seafoods An omega-6 polyunsaturated fatty acid found in corn oil, linseed oil, animal tissues 71 72 Chapter 5 Carboxylic Acids and Esters

Triglycerides (Fats and Oils) O

O O O O R O O O O O R OOR O O O O O O O O Triglycerides R O fats and oils () O O C(CH ) CH O R O 2 12 3 R O O O O O O C(CH2)12CH3 O O O O Tristearin O C(CH2)16CH3 O One of the principle O C(CH2)12CH3 compounds in beef fat and O O cocoa butter; triglycerides such Trimyristin as this lubricate meat fibers, C(CH2)16CH3 Found in nutmeg, a spice and make the meat more O Olestra obtained from the seed of tender when cooked; the A substitute for dietary fats developed by Procter & Gamble after 30 years and the nutmeg tree, found in yellow color of beef fat comes $200 million dollars worth of research; it is a combination of sucrose and fatty acids O obtained from soybean oil and cottonseed oil; it is too hindered for digestive Indonesia and the West from carotene dissolved in C(CH ) CH 2 16 3 enzymes to react with; can carry small amounts of fat-soluble vitamins out of Indies, and other tropical tristearin. intestinal tract areas O 73 74

Saponification of Triglycerides Fatty Acid Salts (Chewing the Fat) • Triglycerides can be broken apart under basic • Salts of fatty acids combine two different solubility conditions (a saponification reaction) to produce characteristics: long-chain carboxylate salts. – a long, nonpolar, water-insoluble (hydrophobic) O hydrocarbon “tail.” – a charged, water-soluble (hydrophilic) “head.” CH2 OC(CH2)16CH3 O CH OH O 2 O NaOH + - CH OC(CH2)16CH3 Na O C(CH2)16CH3 CH OH O- Na+ O Sodium stearate Nonpolar, hydrophobic tail Polar, hydrophilic head - a carboxylate salt CH2 OH (water insoluble) CO2 (water soluble) CH OC(CH ) CH 2 2 16 3 glycerol glyceryl tristearate (tristearin) • When these substances are placed in water, their a triglyceride “tails” become tangled, thereby dissolving each other, leaving the charged, hydrophilic portions • Unlike their carboxylic acid forms, the carboxylate sticking out into the solution, allowing the whole salts are at least somewhat soluble in water. 75 micelle to dissolve in water, acting as a soap. 76

Soap Soaps and Detergents O (Cleanliness, As They Say, Is Next To Impossible) O- Na+ Sodium stearate O

O- Ca2+ Calcium stearate 2 "soap scum"

- Grease CO2 Sodium Alkylbenzenesulfonate a synthetic detergent - + SO3 Na

Sodium para-Dodecylbenzenesulfonate a biodegradable detergent - + SO3 Na OH O 77 Polyoxyethylene 78 a soap micelle A nonionic synthetic detergent; causes less foaming. Chapter 5 Carboxylic Acids and Esters

Esters of Inorganic Acids O O H+ ROHHO P OH ROP OH an alcohol OH OH phosphoric acid a phosphate ester Esters of Inorganic (monoester) Acids ROH O O ROH ROP OR ROP OH

OR OR a phosphate triester a phosphate diester 79 80

Some Important Phosphate Esters NH2 N N adenine O O O O O - N CH OPO - CH N 2 - O P O 2 NH2 RO P O P OOP O - - O O deoxyribose O N O- O- O- cytosine OH O a phosphate triester O N NH - 2 O P O CH2 O O HO OH O N HN OH N guanine glucose-6-phosphate N O Adenine H2N N - N O O O O P O CH2 O O N O CH - N 3 CH2 HN O P O P O P O thymine O O - - - - O N O O O O P O CH2 O (ATP) Deoxyribonucleic Acid O (DNA) OH 81 82 OH OH

Reactions of Carboxylic Acids 5. Reaction of an acid anhydride with an alcohol to produce an ester and a carboxylic acid. O O O O 1. Reaction of a carboxylic acid with water to form a carboxylate ion. O O C C ++H O R' C R' C H + R O R alcohol R O R O RC + H2O RC + H O 3 acid anhydride or phenol ester carboxylic acid O H O- carboxylic acid carboxylate ion 6. Hydrolysis of an ester to produce a carboxylic acid and an alcohol. O O 2. Reaction of a carboxylic acid with a base to form a carboxylate salt and water. H+ O O C R' H O C H + H O R' + 2  RC + NaOH RC + H O R O R O alcohol 2 ester carboxylic acid O H O- Na+ carboxylic acid carboxylate salt 7. Saponification of an ester to produce a carboxylate salt and an alcohol. O O 3. Reaction of a carboxylic acid with an alcohol to produce an ester and water. O O C R' + NaOH C + H O R' - + H+ R O R O Na alcohol C H ++H O R' C R'H O H ester  carboxylate salt R O alcohol R O ester carboxylic acid or phenol 8. Formation of a phosphate monoester. O O 4. Reaction of an acid chloride with an alcohol to produce an ester and HCl. H+ O O HOP OH + ROH ROP OH + H2O alcohol C ++H O R' C R'H Cl OH OH R Cl R O alcohol 83 phosphoric acid phosphate monoester 84 acid chloride or phenol ester