chapter 16 carboxylic acids and esters - cerritos...

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Chapter 16 Carboxylic Acids and

Esters

16.1

Carboxylic Acids

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Publishing as Benjamin Cummings

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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—OH hydroxyl group or CH3COOH

carboxyl group

Carboxylic Acids

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Models of Carboxylic Acids

� The three-dimensional models show the geometry of atoms in carboxylic acid molecules.

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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—OH4 3 2 1

3-methylbutanoic acid

IUPAC Names

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Alpha Hydroxy Acids

Alpha hydroxy acids

(AHAs)

� Occur naturally in fruit, milk, and

sugarcane.

� Are used in skin

care products.

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Names and Sources of Some

Carboxylic Acids

TABLE 16.1

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Aromatic Carboxylic Acids

OHC

O

OHC

O

OHC

O

ClNH2

benzoic acid 3-chlorobenzoic acid 4-aminobenzoic acid

m-chlorobenzoic acid p-aminobenzoic acid

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16.2 Properties of Carboxylic Acids

Chapter 16 Carboxylic Acids and

Esters

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Publishing as Benjamin Cummings

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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 dimers in 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

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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

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Solubility in Water

Carboxylic acids

� Form hydrogen

bonds with many water molecules.

� With 1-4 carbon

atoms are very

soluble in water.

Water molecules

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Boiling Points and Solubility

TABLE 16.2

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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

+

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Chapter 16 Carboxylic Acids and

Esters

16.3 Esters

16.4 Naming Esters

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Esters

In an ester,

� The H in the carboxyl group is replaced

with an alkyl group.

O||||||||

CH3 — C—O—CH3

ester group

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Esterification is

� The reaction of a carboxylic acid and alcohol in the

presence of an acid catalyst to produce an ester.

O

|| H+

CH3—C—OH + H—O—CH2—CH3

O

||

CH3—C—O—CH2—CH3 + H2Oethyl acetate (an ester)

Esterification

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Naming Esters

The name of an ester contains the names of

� The alkyl group from the alcohol.

� The carbon chain from the acid with –ate ending.

from alcohol from acid

O

methyl ||

CH3— O—C —CH3

ethanoate (acetate)

IUPAC: methyl ethanoate

common: methyl acetate

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Ester Products

Aspirin

� Is used to relieve pain and reduce inflammation.

� Is an ester of salicylic acid and acetic acid.

Oil of wintergreen

� Is used to soothe sore muscles.

� Is an ester of salicylic acid and methanol.

CH3

O

CO

OH

O

C

OH

CH3O

O

C

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Esters in Plants

Esters give flowers and

fruits their

pleasant

fragrances and

flavors.

TABLE 16.4

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Learning Check

Give the IUPAC and common names of the following compound, which is responsible for the flavor and odor

of pears.

O

||

CH3—C—O—CH2—CH2—CH3

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Give the IUPAC and common names of the following compound, which is responsible for the flavor and odor of pears.

from 1-propanolO||

CH3—C—O—CH2—CH2—CH3

Propyl ethanoate (IUPAC)

Propyl acetate (common)

Solution

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Learning Check

Name the following esters:O

║A. CH3—CH2—CH2—C—O—CH3

O||

B. CH3—CH2 —C—O—CH2—CH3

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Solution

A. Methyl butanoate (methyl butyrate)

B. Ethyl propanoate (methyl propionate)