Carboxylic Acids And Esters

Carboxylic Acids, Esters, Amines and Amides Carboxylic Acids Properties of Carboxylic Acids Esters Esterification and Hydrolysis

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Carboxyl Group Carboxylic acids contain the carboxyl group on carbon 1. O || CH3 — C—OH = CH3—COOH carboxyl group 2

Naming Carboxylic Acids Formula

IUPAC alkan -oic acid

Common prefix – ic acid

HCOOH

methanoic acid

formic acid

CH3COOH

ethanoic acid

acetic acid

CH3CH2COOH

propanoic acid

propionic acid

CH3CH2CH2COOH butanoic acid

butyric acid 3

Naming Rules • Identify longest chain • (IUPAC) Number carboxyl carbon as 1 • (Common) Assign α, β, χ to carbon atoms adjacent to carboxyl carbon CH3 | CH3 — CH—CH2 —COOH IUPAC 3-methylbutanoic acid Common β-methylbutryic acid 4

Learning Check CA1 Give IUPAC and common names: A.

CH3COOH CH3 |

B.

CH3CHCOOH 5

Solution CA 1 A.

CH3COOH ethanoic acid; acetic acid CH3 |

B.

CH3CHCOOH 2-methylpropanoic acid; α-methylpropionic acid 6

Properties • Carboxylic acids are weak acids CH3COOH + H2O • Neutralized by a base CH3COOH + NaOH

CH3COO– + H3O+

CH3COO– Na+ + H2O

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Esters In and ester, the H in the carboxyl group is replaced with an alkyl group O ||

CH3 — C—O —CH3 = CH3—COO —CH3 ester group 8

Esters in Plants Esters give flowers and fruits their pleasant fragances and flavors.

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Naming Esters • Name the alkyl from the alcohol –O• Name the acid with the C=O with –ate acid alcohol O || methyl CH3 — C—O —CH3 Ethanoate (acetate)

methyl ethanoate (IUPAC) methyl acetate (common) 10

Some Esters and Their Names Flavor/Odor Raspberries HCOOCH2CH3

ethyl methanoate (IUPAC) ethyl formate (common)

Pineapples CH3CH2CH2 COOCH2CH3 ethyl butanoate (IUPAC) ethyl butyrate (common) 11

Learning Check CA 2 Give the IUPAC and common names of the following compound, which is responsible for the flavor and odor of pears. O ||

CH3 — C—O —CH2CH2CH3 12

Solution CA2 O ||

propyl

CH3 — C—O —CH2CH2CH3 propyl ethanoate (IUPAC) propyl acetate (common) 13

Learning Check CA 3 Draw the structure of the following compounds: C. 3-bromobutanoic acid E. Ethyl propionoate

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Solution CA 3 A. 3-bromobutanoic acid Br | CH3CHCH2COOH B. Ethyl propionoate O ||

CH3 CH2 COCH2CH3 CH3CH2COOCH2CH3 15

Esterification • Reaction of a carboxylic acid and alcohol • Acid catalyst O || H+ CH3 — C—OH + HO—CH2CH3 O || CH3 — C—O—CH2CH3 + H2O

16

Hydrolysis • Esters react with water and acid catalyst • Split into carboxylic acid and alcohol O || H+ H — C—O—CH2CH3 + H2O O

||

H — C—OH

+ HO—CH2CH3 17

Saponification • Esters react with a bases • Produce the salt of the carboxylic acid and alcohol O || CH3C—OCH2CH3 + NaOH O || CH3C—O– Na+ salt of carboxylic acid

+

HOCH2CH3 18

Learning Check CA4 Write the equation for the reaction of propionic acid and methyl alcohol in the presence of an acid catalyst.

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Solution CA4 O ||

H+

CH3CH2COH + HOCH3 O || CH3CH2COCH3 +

H2O 20

Learning Check CA5 What are the organic products when methylacetate reacts with A. Water and an acid catalyst? B. KOH?

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Solution CA5 A.

O ||

CH3COH

+

HOCH3

O ||

B.

CH3CO– K+

+ HOCH3 22