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

IUPAC Names for Carboxylic AcidsMany carboxylic acids are still named by their common names, which use prefixes: form, acet, propion, butyr.. Naming Carboxylic Acids Give the IUPAC and c

Karen C Timberlake

Lecture Presentation

Chapter 16 Carboxylic Acids

and Esters

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

Chapter 16 Readiness

Core Chemistry Skills

• Writing Equations for Reactions of Acids and

Bases (11.7)

• Naming and Drawing Alkanes (12.2)

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

IUPAC Names for Carboxylic Acids

In the IUPAC names of carboxylic acids,

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

IUPAC Names for Carboxylic Acids

Substituents are numbered from the carboxyl, which is

carbon 1

IUPAC Names for Carboxylic Acids

• As before, for benzoic acid, the placement of substituents is

shown using the prefixes ortho, meta, and para

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

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)

Guide to Naming Carboxylic Acids

Naming Carboxylic Acids

Give the IUPAC and common name for the following

ANALYZE Given Need THE carboxylic acid IUPAC and PROBLEM common name

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

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.

Study Check

Give the IUPAC name of each compound

A

B.

Study Check

Draw the line-angle structure for

4-chlorohexanoic acid.

Draw the line-angle structure for

4-chlorohexanoic acid.

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

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

Chemistry Link to Health:

Alpha Hydroxy Acids

Several different alpha hydroxy acids may be found in skin

care products singly or in combination

Chemistry Link to Health:

Alpha Hydroxy Acids

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

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)

Boiling Points of Carboxylic Acids

• The polar carboxyl groups allow carboxylic acids to form

multiple hydrogen bonds with other carboxylic acid

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

Study Check

Match each of the compounds 2-butanol, pentane, and

propanoic acid with the boiling points 141°C, 100°C, and 36°C (They have about the same molar mass.)

Match each of the compounds 2-butanol, pentane, and

propanoic acid with the boiling points 141°C, 100°C, and 36°C (They have about the same molar mass.)

Boiling points increase due to

• increased formation of hydrogen bonds

• increased dipole–dipole attractions

• increasing molar mass

Match each of the compounds 2-butanol, pentane, and

propanoic acid with the boiling points 141°C, 100°C, and 36°C (They have about the same molar mass.)

• Pentane, an alkane, cannot form hydrogen bonds It has the lowest boiling point, 36°C

• 2-Butanol, an alcohol, can form hydrogen bonds, so it has a higher boiling point, 100°C

• Propanoic acid, a carboxylic acid, can form dimers

increasing the effective molar mass It therefore has the

highest boiling point, 141°C

Solubility in Water

Carboxylic acids

• form hydrogen bonds with

many water molecules

• with one to five carbon

atoms are very soluble in

water

• are less soluble as the

number of carbons increases

Acetic acid forms hydrogen bonds with water molecules.

Acidity of Carboxylic Acids

Carboxylic acids

• are weak acids

• dissociate in water to produce carboxylate ions and

hydronium ions

• can lose a proton because two oxygen atoms in a

carboxylate ion stabilize negative charge

Properties of Carboxylic Acids

Study Check

Write the balanced equation for the ionization of butanoic acid

in water and identify the carboxylate ion

butanoic acid

Solution

Write the balanced equation for the ionization of butanoic acid

in water and identify the carboxylate ion

+ H2O

+ H3O+

carboxylate ion

Neutralization of Carboxylic Acids

Carboxylate salts are a product of the neutralization of a

carboxylic acid with a strong base such as NaOH or KOH

The carboxylate ion is named by replacing the ic acid ending of the acid name with ate.

Neutralization of Carboxylic Acids

Carboxylate salts

• are ionic compounds with strong attractions between

positively charged metal ions such as Li+, Na+, and K+ and the negatively charged carboxylate ion

• are solids at room temperature

• have high melting points

• are usually soluble in water

Carboxylic Acids, Preservatives

• Sodium propionate, a preservative, is added to bread,

cheeses, and bakery items to inhibit the spoilage of the food

by microorganisms

• Sodium benzoate is added to juices, margarine, relishes,

salads, and jams to inhibit the growth of mold and bacteria

Carboxylic Acids, Preservatives

• Monosodium glutamate (MSG) is added to meats, fish,

vegetables, and bakery items to enhance flavor, although it may cause headaches in some people

Study Check

Write the equation for the reaction of propanoic acid

with NaOH

Write the equation for the reaction of propanoic acid

with NaOH

Chemistry Link to Health:

Carboxylic Acids in Metabolism

At the pH of the aqueous environment in the cells,

• the carboxylic acids are dissociated

• it is actually the carboxylate ions that take part in the

reactions of the citric acid cycle

For example, in water, succinic acid is in equilibrium with its

carboxylate ion, succinate

Chemistry Link to Health:

Carboxylic Acids in Metabolism

Carboxylates are part of the metabolic processes within our

cells For example,

• during glycolysis, a molecule of glucose is broken down

into two molecules of pyruvate, the carboxylate salt of

pyruvic acid

• during strenuous exercise when oxygen levels are low

(anaerobic), pyruvate is reduced to give lactic acid or the

lactate ion

Chemistry Link to Health:

Carboxylic Acids in Metabolism

In the citric acid cycle (Krebs cycle),

• di- and tricarboxylates are oxidized and

decarboxylated (loss of CO2) to produce

energy for cells.

• citrate, with six carbons, is oxidized to a

five-carbon

α-ketoglutarate:

Chemistry Link to Health:

Carboxylic Acids in Metabolism

The citric acid cycle continues as

• α-ketoglutarate loses CO2 to give a four-carbon succinate

• a series of reactions then converts succinate to oxaloacetate

16.3 Esters

By the 1800s, chemists had

discovered that

• salicin from willow tree bark and

leaves was responsible for pain

relief.

• the body converts salicin to

salicylic acid, which irritates the

stomach lining

Bayer discovered that an ester form

of the compound, acetylsalicylic acid,

is less irritating but still effective

Learning Goal Write a balanced chemical equation for the

Esters are

• synthesized from the reaction of a carboxylic acid

and alcohol.

• found in fats and oils.

• responsible for the aroma and flavor of bananas,

oranges, and strawberries.

Esterification is

• the reaction of a carboxylic acid and alcohol in the presence

of an acid catalyst and heat to produce an ester

• the replacement of the hydrogen atom in the carboxylic acid

—OH group with an alkyl group from an alcohol

• an equilibrium reaction; an excess of the alcohol reactant is used to shift the equilibrium in the direction of the formation

of the ester product

In 1899, the Bayer chemical company

• produced an ester of salicylic acid and acetic acid less

irritating to the stomach than salicylic acid

• called the ester acetylsalicylic acid (aspirin)

Many people take a daily low-dose aspirin, which has been

found to lower the risk of heart attack and stroke

Chemistry Link to Health:

Salicylic Acid from a Willow Tree

Oil of wintergreen, or methyl salicylate, has a pungent, minty odor and flavor and

• is used in skin ointments

• can pass through the skin

• acts as a counter-irritant, producing heat to soothe sore

muscles

Chemistry Link to Health:

Salicylic Acid from a Willow Tree

Dacron has many uses; it

• forms a permanent-press fabric that resists wrinkles.

• is used to make artificial blood vessels and valves that are

biologically inert and does not clot blood.

• Is made into a film called Mylar and a plastic known as PETE

(polyethyleneterephthalate) used for plastic drink bottles.

Chemistry Link to Environment:

Plastics

16.4 Naming Esters

Esters such as ethyl butanoate

provide the odor and flavor of

many fruits, such as pineapples

Learning Goal Write the IUPAC and common names for

esters; draw condensed and line-angle structural formulas

Naming Esters

The name of an ester consists of two words:

1 The first word indicates the alkyl part from the alcohol.

2 The second word is the carboxylate name of the

carboxylic acid

Naming Esters

Esters have IUPAC and common names:

Guide to Naming Esters

Naming Esters

What is the IUPAC name of the following ester?

STEP 1 Write the name for the carbon chain from an

alcohol as an alkyl group

Naming Esters

What is the IUPAC name of the following ester?

STEP 2 Change the ic acid of the acid name to ate.

Study Check

Give the IUPAC and common names for the following

compound, responsible for the flavor and odor of pears:

Give the IUPAC and common names for the following

compound, responsible for the flavor and odor of pears:

STEP 1 Write the name for the carbon chain from

an alcohol as an alkyl group

Give the IUPAC and common names for the following

compound, responsible for the flavor and odor of pears:

STEP 2 Change the ic acid of the acid name to ate.

propyl

ethanoate propyl acetate

Esters in Fruits

• Many of the fragrances of

perfumes and flowers and

the flavors of fruits are due

to esters

• Small esters are volatile, so

we can smell them, and they

are soluble in water, so we

can taste them

• The odor of grapes is due to

ethyl heptanoate

Esters in Fruits and Flavoring

Draw the condensed structural formulas for each of the

following compounds:

A propyl pentanoate

B ethyl propionate

Study Check

Draw the condensed structural formulas for each of the

following compounds:

A propyl pentanoate

B ethyl propionate

Solution

16.5 Properties of Esters

Ethyl acetate is the solvent in

fingernail polish, plastics, and

lacquers

Learning Goal Describe the

boiling points and solubility of

esters; draw the condensed

structural formulas for the

hydrolysis products

Boiling Points of Esters

Esters have

• boiling points higher than those of alkanes and ethers

• boiling points lower than those of alcohols and carboxylic

acids of similar mass

Because ester molecules do not have hydroxyl groups, they

cannot hydrogen bond to each other

Solubility of Esters in Water

• Esters are soluble if they

have two to five carbon

atoms As the number of

carbons increases from five,

their solubility in water

decreases

• The partially negative

oxygen of the carbonyl

group forms hydrogen

bonds with the partially

positive hydrogen atoms of

water molecules

Acid Hydrolysis of Esters

In acid hydrolysis,

• an ester reacts with water to produce a carboxylic acid

and an alcohol

• a water molecule provides an —OH group to convert the

carbonyl group of the ester to a carboxyl group

• an acid catalyst and heat are required

Acid Hydrolysis of Esters

Aspirin that has been stored for a long time may

undergo hydrolysis in the presence of water and heat

Base Hydrolysis (Saponification)

Base hydrolysis, or saponification,

presence of heat.

Ethyl acetate is a solvent used in fingernail polish,

plastics, and lacquers

Write the balanced chemical equation for the

hydrolysis of ethyl acetate with NaOH.

Write equation for reaction of ethyl acetate and

NaOH, in sample problem 16.8

ANALYZE Given Need THE ester, base carboxylate salt PROBLEM and alcohol

ANALYZE Given Need THE ester, base carboxylate salt PROBLEM and alcohol

Concept Map