General organic and biological chemistry structures off life 5th CH16 carboxylic acids GOB structures 5th ed

Lecture Presentation

Chapter 16

Carboxylic Acids
and Esters

Karen C. Timberlake

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Chapter 16 Carboxylic Acids and Esters

Surgical technicians prepare the operating room and
the patients for surgery by

•
•

creating a sterile environment in the surgical room.
washing, shaving, and disinfecting incision sites.

During the surgery, a surgical technician provides the
sterile instruments and supplies to the surgeons and
surgical assistants.

General, Organic, and Biological Chemistry: Structures of Life, 5/e

Karen C. Timberlake

© 2016 Pearson Education, Inc.


Chapter 16 Readiness

Core Chemistry Skills

•

Writing Equations for Reactions of Acids and
Bases (11.7)

•

Naming and Drawing Alkanes (12.2)

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


16.1 Carboxylic Acids

A carboxylic acid contains a carboxyl group, which consists of a hydroxyl group —OH attached to the
carbon in a carbonyl group.

Learning Goal Write the IUPAC and common names for carboxylic acids, and draw their condensed and

line-angle structural formulas.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


IUPAC Names for Carboxylic Acids

In the IUPAC names of carboxylic acids,

•

the e in the alkane name is replaced with oic acid.

CH4

Methane

Methanoic acid

CH3—CH3

Ethane

Ethanoic acid

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


IUPAC Names for Carboxylic Acids

Substituents are numbered from the carboxyl, which is
carbon 1.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


IUPAC Names for Carboxylic Acids

•

As before, for benzoic acid, the placement of substituents is shown using the prefixes ortho, meta, and
para.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


IUPAC Names for Carboxylic Acids

Many carboxylic acids are still named by their common names, which use prefixes: form, acet, propion, butyr.

•

When using the common names, the Greek letters alpha (α), beta (β), and gamma (γ) are assigned to
the carbons adjacent to the carboxyl carbon.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Common Carboxylic Acids

A red ant sting contains methanoic acid (formic
acid) that irritates the skin.

The sour taste of vinegar is due to ethanoic acid
(acetic acid).

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Guide to Naming Carboxylic Acids

General, Organic, and Biological Chemistry: Structures of Life, 5/e

Karen C. Timberlake

© 2016 Pearson Education, Inc.


Naming Carboxylic Acids

Give the IUPAC and common name for the following carboxylic acid:

ANALYZE

Given

THE

carboxylic acid

PROBLEM

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

Need
IUPAC and
common name

© 2016 Pearson Education, Inc.


Naming Carboxylic Acids

Give the IUPAC and common name for the following carboxylic acid:

STEP 1 Identify the longest carbon chain and replace
the e in the alkane name with oic acid.
The IUPAC name for a carboxylic acid with three
carbons is propanoic acid. The common name is
propionic acid.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Naming Carboxylic Acids

Give the IUPAC and common name for the following carboxylic acid:

STEP 2 Name and number any substituents by
counting the carboxyl group as carbon 1.

IUPAC name
Common name

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

2-methylpropanoic acid
2-methylpropionic acid

© 2016 Pearson Education, Inc.


Study Check

Give the IUPAC name of each compound.

A.

B.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Solution

Give the IUPAC name of each compound.

A.
3-hydroxypentanoic acid
3-bromobenzoic acid
B.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Study Check

Draw the line-angle structure for
4-chlorohexanoic acid.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Solution

Draw the line-angle structure for
4-chlorohexanoic acid.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Preparation of Carboxylic Acids

Carboxylic acids

•

•

can be prepared from primary alcohols or aldehydes.
can be produced from the oxidation of primary alcohols to aldehydes and then to carboxylic acids.

Ethanol in wine is oxidized by oxygen in the air, converting the primary alcohol to acetaldehyde and then to
acetic acid, the carboxylic acid in vinegar.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Chemistry Link to Health:
Alpha Hydroxy Acids

Alpha hydroxy acids (AHAs)

•
•

are found in fruits, milk, and sugar cane.
are naturally occurring carboxylic acids with a hydroxyl group on the carbon atom that is adjacent to the

carboxyl group.

Dermatologists have been using products with high concentrations (20–70%) of AHAs to remove acne scars
and in skin peels to reduce irregular pigmentation and age spots.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Chemistry Link to Health:
Alpha Hydroxy Acids

Several different alpha hydroxy acids may be found in skin care products singly or in combination.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


16.2 Properties of Carboxylic Acids

Carboxylate salts are often
used as preservatives and
flavor enhancers in soups
and seasonings.
Sodium propionate, a preservative, is added to

cheeses, bread, and other bakery items to inhibit the
spoilage of the food by microorganisms.

Learning Goal Describe the boiling points, solubilities, dissociation, and neutralization of carboxylic
acids.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Polarity of Carboxylic Acids

Carboxylic acids are strongly polar because they have two polar groups:

•
•

a hydroxyl group (—OH) and
a carbonyl group (C = O).

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Boiling Points of Carboxylic Acids

•

The polar carboxyl groups allow carboxylic acids to form multiple hydrogen bonds with other carboxylic
acid molecules.

•

This effect of hydrogen bonds gives carboxylic acids higher boiling points than alcohols, ketones, and
aldehydes of similar molar mass.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Carboxylic Acids, Dimers

•

The higher boiling points
of carboxylic acids can also be attributed to
the formation of dimers between two
carboxylic acids.

•

Two hydrogen bonds form between their
carboxyl groups, which effectively double the
mass of the molecule, increasing the
temperature required to reach the boiling

point.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.