chapter sixteen carboxylic acids, esters, and other acid derivatives

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Chapter Chapter Sixteen Sixteen Carboxylic Acids, Esters, and Other Acid Derivatives

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Chapter SixteenChapter SixteenCarboxylic Acids, Esters, and Other Acid Derivatives

Chapter 16 | Slide 2 of 39

Fig. 16.1 The three simplest carboxylic acids: methanoic acid, ethanoic acid, and propanoic acid.

Carboxylic Acids

Chapter 16 | Slide 3 of 39

→ Fig. 16.2Benzoic acid molecule

Carboxylic Acids

Chapter 16 | Slide 4 of 39

Carboxylic acids contain the carboxyl group on carbon 1.• A carboxyl group is a carbonyl attached to a hydroxyl

• Acts differently than an alcohol or a carbonyl compound

O

CH3 — C—OH = CH3—COOH

carboxyl group

Carboxylic Acids

Chapter 16 | Slide 5 of 39

Formula IUPAC Common alkan -oic acid prefix – ic acid

HCOOH methanoic acid formic acid

CH3COOH ethanoic acid acetic acid

CH3CH2COOH propanoic acid propionic acid

CH3CH2CH2COOH butanoic acid butyric acid

Naming Carboxylic Acids

Chapter 16 | Slide 6 of 39

• Identify longest chain containing the carboxyl group• (IUPAC) Number carboxyl carbon as 1• (Common) Assign , , to carbon atoms adjacent to

carboxyl carbon

CH3

|

CH3 — CH—CH2 —COOHIUPAC 3-methylbutanoic acidCommon -methylbutryic acid

Naming Rules

Chapter 16 | Slide 7 of 39

Aromatic Carboxylic Acids

• Benzoic Acid is the aromatic carboxylic acid• Locates substituents by assigning 1 to the carbon with the

carboxyl group

C

O OH

C

O OH

Cl

C

O OH

CH3

Benzoic acid 3-chlorobenzoic acid

4-methylbenzoic acid

Chapter 16 | Slide 8 of 39

Chapter 16 | Slide 9 of 39

Chapter 16 | Slide 10 of 39

Properties of Carboxylic Acids

• Like alcohols, carboxylic acids form strong intermolecular hydrogen bonds.

• Most carboxylic acids exist as dimers.– Boiling points higher than alkanes of similar MW.– Small carboxylic acids (1-4 carbons) are soluble in

water

H3C

O

O H

H

O

O

CH3

Chapter 16 | Slide 11 of 39

Chapter 16 | Slide 12 of 39

Synthesis of Carboxylic Acids

• Synthesized from aromatic rings, primary alcohols and aldehydes.

Oxidizing agent

R

R OH

R

O

CarboxylicAcid

Chapter 16 | Slide 13 of 39

Oxidation of Aromatic Compounds

• Benzene does not react with KMnO4.

• Alkyl groups on the ring (-R) are readily oxidized though.

• One product for all reactions.

R

+ KMnO4

O

OH

Chapter 16 | Slide 14 of 39

Oxidation of Aromatic Compoundswith KMnO4

O

OH

Chapter 16 | Slide 15 of 39

• Oxidation of primary alcohols and aldehydes:

R

OH

CrO3, H3O+

or Na2Cr2O7, H2O, CH3CO2HR

O

OH

R

O

AgNO3NH4OH

H R

O

OH

Chapter 16 | Slide 16 of 39

• Oxidation of alcohols to carboxylic acids.

OH

CrO3, H3O+

O

HO

OH

CrO3, H3O+

O

OH

Chapter 16 | Slide 17 of 39

• Carboxylic acids are weak acids– Stronger acids than alcohols

CH3COOH + H2O CH3COO– + H3O+

• Neutralized by a base

CH3COOH + NaOH CH3COO– Na+ + H2O

Properties

Chapter 16 | Slide 18 of 39

• Carboxylic acids are obviously acidic.• Stronger acids than alcohols, but weaker than mineral

acids.• Will react with NaOH to give metal carboxylates.• There is a large range of acidities depending on the

substituents on a carboxylic acid.

O

R OH

+ NaOH

O

R O-Na+

+ H2O

Chapter 16 | Slide 19 of 39

Carboxylate Ions

• The conjugate base of a carboxylic acid– Formed when a carboxylic acid loses a proton– Named by dropping the -ic acid ending and replacing it

with –ate

• CH3CH2COO- Propionate

• CH3COO- Ethanoate (Acetate)

• CH3CH2CH2COO- Butanoate

Chapter 16 | Slide 20 of 39

Carboxylate Salts

• An ionic compound in which the negative ion is a carboxylate ion– Naming: the positive ion is named first, followed by a

separate word giving the name of the negative ion– Converted back to a carboxylic acid by the addition of a

strong acid

• CH3CH2COO-Na+ Sodium Propionate• CH3COO-K+ Potassium Ethanoate• CH3CH2CH2COO-Li+ Lithium Butanoate

Chapter 16 | Slide 21 of 39

Table 16.3

Carboxylic Acids

Chapter 16 | Slide 22 of 39

← Fig. 16.12 Methyl and ethyl esters of acetic acid.

Esters

Chapter 16 | Slide 23 of 39

In an ester, the H in the carboxyl group is replaced with an alkyl group

O

CH3 — C—O —CH3 = CH3—COO —CH3

ester group

Sulfur analogs of esters are called thioesters (sulfur replaces the hydroxyl oxygen)

Ester

Chapter 16 | Slide 24 of 39

• 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 methyl ethanoate (IUPAC)

(acetate) methyl acetate (common)

Naming Esters

Chapter 16 | Slide 25 of 39

Chapter 16 | Slide 26 of 39

Esters

Chapter 16 | Slide 27 of 39

• Reaction of a carboxylic acid and alcohol• Acid catalyst

O H+

CH3 — C—OH + HO—CH2CH3

O

CH3 — C—O—CH2CH3 + H2O

Esterification: Preparation of Esters

Chapter 16 | Slide 28 of 39

• 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

Hydrolysis: Breaking Up Esters

Chapter 16 | Slide 29 of 39

Hydrolysis

Chapter 16 | Slide 30 of 39

• Esters react with bases • Produce the salt of the carboxylic acid and alcohol

O H2O

CH3C—OCH2CH3 + NaOH

O

CH3C—O– Na+ + HOCH2CH3

salt of carboxylic acid

• Saponification reactions produce soaps

Saponification

Chapter 16 | Slide 31 of 39

Soaps

• Carboxylate salts

Chapter 16 | Slide 32 of 39

• The following figure represents soap.

• Which end of the anion is hydrophobic?

Chapter 16 | Slide 33 of 39

• How does soap interact with grease?

Chapter 16 | Slide 34 of 39

Chapter 16 | Slide 35 of 39

Chapter 16 | Slide 36 of 39

Chapter 16 | Slide 37 of 39

Dicarboxylic Acids

Chapter 16 | Slide 38 of 39

The C2 dicarboxylic acid, oxalic acid, contributes to the tart taste of rhubarb stalks.

Chapter 16 | Slide 39 of 39

Polyfunctional Carboxylic Acids

• Carboxylic acids that contain one or more additional functional groups– Unsaturated acids

• Contain a multiple bond

– Hydroxy acids• Contains an additional hydroxyl group

– Keto acids• Contains an additional carbonyl group

• Many monoacids and polyfunctional carboxylic acids are intermediates in metabolic reactions