Carboxylic acids & esters

The IUPAC names of carboxylic acids  Replace the -e in the alkane name with -oic acid.. The common names of simple carboxylic acids Are formic acid 1C, acetic acid 2C, propionic acid 3

Chapter 16 Carboxylic Acids and Esters

16.1 Carboxylic Acids

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.

Models of Carboxylic Acids

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

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—OH

4 3 2 1

IUPAC Names

The common names of simple carboxylic acids

 Are formic acid (1C), acetic acid (2C), propionic acid (3C), and butyric acid (4C)

HCOOH formic acid CH3—COOH acetic acid

 Locate substituents using α, β, γ for the carbon atoms adjacent

to the carboxyl carbon.

CH3

γ β| α

Common Names

Alpha Hydroxy Acids

Alpha hydroxy acids

Names and Sources of Some

Carboxylic Acids

TABLE 16.1

Common Carboxylic Acids

Methanoic acid (formic acid)

Aromatic Carboxylic Acids

Benzoic acid

 Is the aromatic carboxylic acid.

 Locates substituents by assigning 1 to the carbon attached to the carboxyl group.

 Has common names that assign prefixes ortho, meta, and para

for 2 substituents.

ortho 1, 2 location

meta 1, 3 location

Aromatic Carboxylic Acids

OH C

O

OH C

O

OH C

O

Cl

NH2

Give the IUPAC and common names:

A CH3—COOH

CH3 |

B CH3—CH—COOH

C.

Learning Check

COOH

A CH3—COOH ethanoic acid (acetic acid)

CH3 |

B CH3—CH—COOH 2-methylpropanoic acid

Learning Check

Give the IUPAC and common names for the following:

A CH3─CH2─COOH

CH3 |

B CH3─CH─CH2─COOH

C.

OH C

O

A CH3─CH2─COOH propanoic acid

(propionic acid)

CH3 |

B CH3─CH─CH2─COOH 3-methylbutanoic acid

(β-methylbutyric acid)

C 3-bromobenzoic acid

(m-bromobenzoic acid)

OH C

O

Preparation of Carboxylic Acids

 Carboxylic acids can be prepared by oxidizing primary alcohols

ethanol ethanal ethanoic acid

(ethyl alcohol) (acetaldehyde) (acetic acid)

Learning Check

What alcohol could be used to prepare the following:

1 butanoic acid

2 propanoic acid

16.2 Properties of Carboxylic Acids

Chapter 16 Carboxylic Acids and

Esters

Polarity of Carboxylic Acids

Carboxylic acids

 Are strongly polar.

 Have two polar groups:

hydroxyl (−OH) and carbonyl (C=O).

O

║δ+ δ- δ+

CH3CO H

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

| ||

Comparison of Boiling Points

Compound Molar Mass Boiling Point

Solubility in Water

Carboxylic acids

 Form hydrogen bonds

with many water

molecules.

 With 1-4 carbon atoms

are very soluble in water.

Water molecules

Boiling Points and Solubility

TABLE 16.2

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+

Acid Dissociation Constants

Carboxylic acids

 Have small Ka values.

 Exist mostly as molecules and

a few ions in aqueous

solutions.

TABLE 16.3

Neutralization of Carboxylic Acids

Carboxylic acid salts

 Are a product of the neutralization of a carboxylic acid with a

strong base

CH3—COOH + NaOH CH3—COO– Na+ + H2O

acetic acid sodium acetate

(carboxylic acid salt)

 Are used as preservatives and flavor enhancers.

Learning Check

Write the equation for the reaction of propanoic acid with

A water

B KOH

Chapter 16 Carboxylic Acids and

Esters

16.3 Esters 16.4 Naming Esters

In an ester,

 The H in the carboxyl group is replaced

with an alkyl group.

O

||

CH3 — C—O —CH3

Esterification is

 The reaction of a carboxylic acid and alcohol in the presence of

an acid catalyst to produce an ester.

Write the equation for the reaction of propanoic acid and methanol

in the presence of an acid catalyst

Learning Check

Write the equation for the reaction of propanoic acid

and methanol in the presence of an acid catalyst

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

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 C O

OH

O C

CH3O

O C

Give the IUPAC and common names of the following compound,

which is responsible for the flavor and odor of pears.

from 1-propanol

O

||

CH3—C—O—CH2—CH2—CH3

Propyl ethanoate (IUPAC)

Propyl acetate (common)

Solution

A Methyl butanoate (methyl butyrate)

B Ethyl propanoate (methyl propionate)

CH3—CH2—CH2—C—O—CH2—CH2—CH3

Chapter 16 Carboxylic Acids and

Esters

16.5 Properties of Esters

Base hydrolysis (also called saponification)

 Is the reaction of an ester with a strong base

 Produces the salt of the carboxylic acid and an alcohol.

The base hydrolysis of long chain fatty acids

produces acid salts called “soaps”

Cleaning Action of Soap

A soap

 Contains a nonpolar end

that dissolves in

nonpolar fats and oils,

and a polar end that

dissolves in water.

 Forms groups of soap

molecules called

micelles that dissolve in

water and are washed

away.

Write the organic products when methyl acetate reacts with

A Water and an acid catalyst

B KOH

Learning Check

Write the organic products when methyl acetate reacts with:

A Water and an acid catalyst