Chapter 13 Carboxylic Acids, Esters, Amines, and Amides

Home , Amide, Amide (functional group), Amine, Carboxylic acid, Ester

13.1 Carboxylic Acids

1 Carboxylic Acids

A carboxylic acid contains a carboxyl group, which • is a carbonyl group (C=O) attached to a hydroxyl group (—OH). • is found on carbon 1 in carboxylic acids.

O 

CH3 — C—OH hydroxyl group or CH3COOH carbonyl group

2 Models of Carboxylic Acids

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

3 IUPAC Names

The IUPAC names of carboxylic acids: • Replace the -e in the alkane name with -oic acid.

CH4 methane HCOOH methanoic acid CH —CH ethane CH —COOH ethanoic acid 3 3 3 • Number substituents from the carboxyl carbon 1.

CH3 O | ║ CH3—CH—CH2—C—OH 4 3 2 1 3-methylbutanoic acid

4 Names and Sources of Some Carboxylic Acids

5 Common Carboxylic Acids

Methanoic acid (formic acid) O ║ H─C─OH

ethanoic acid (acetic acid) O ║

CH3─C─OH

6 Aromatic Carboxylic Acids

O Benzoic acid • is the aromatic C OH carboxylic acid. benzoic acid

O O

• locates substituents C OH C OH by numbering the ring from carbon 1 in the carboxyl group. Cl NH2 3-chlorobenzoic acid 4-aminobenzoic acid

7 Learning Check

Give the IUPAC names of each compound.

A. CH3─CH2─COOH propanoic acid

CH3 | B. CH3─CH─CH2─COOH 3-methylbutanoic acid C. O

C OH 3-bromobenzoic acid

8 Chapter 13 Carboxylic Acids, Esters, Amines and Amides

13.2 Properties of Carboxylic Acids

9 Polarity of Carboxylic Acids

Carboxylic acids

• are strongly polar.

• have two polar groups: hydroxyl (−OH) and carbonyl (C=O).

10 Polarity of Carboxylic Acids

Carboxylic acids • form dimers in which hydrogen bonds form between two carboxyl groups.

O H—O || | CH3—C C—CH3 | || O—H O A dimer of acetic acid

• have higher boiling points than alcohols, ketones, and aldehydes of similar mass.

11 Comparison of Boiling Points

Compound Molar Mass Boiling Point O ║

CH3−CH2−C−H 58 49 C

CH3−CH2−CH2−OH 60 97 C

O ║

CH3−C−OH 60 118 C

12 Solubility in Water

Carboxylic acids: Water molecules • form hydrogen bonds with many water molecules.

• with 1-4 carbon atoms are very soluble in water.

13 Boiling Points and Solubility

14 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

15 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.

16 Learning Check

Write the equation for the reaction of propanoic acid with:

A. water – + CH3—CH2—COOH + H2O CH3—CH2—COO + H3O

B. KOH – + CH3—CH2—COOH + KOH CH3—CH2—COO K + H2O

17 Chapter 13 Carboxylic Acids, Esters, Amines, and Amides

13.3 Esters

18 Esters

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

O 

CH3 — C—O —CH3 ester group

19 Esterification

Esterification is the reaction of a carboxylic acid and alcohol in the presence of an acid catalyst to produce an ester. O  H+

CH3—C—OH + H—O—CH2—CH3

O 

CH3—C—O—CH2—CH3 + H2O ethyl acetate (an ester)

20 Learning Check

Write the equation for the reaction of propanoic acid and methanol in the presence of an acid catalyst. O  H+

CH3—CH2—C—OH + H—O—CH3 propanoic acid methanol

O  CH3—CH2—C—O—CH3 + H2O

21 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.

22 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. methyl ethanoate (acetate) O 

CH3— O—C —CH3

IUPAC: methyl ethanoate common: methyl acetate

23 Esters in Plants

Esters give flowers and fruits their pleasant fragrances and flavors.

24 Learning Check

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)

25 Learning Check

Draw the structure of the following compounds.

A. 3-bromobutanoic acid

Br | CH3—CH—CH2—COOH

B. ethyl propionoate O 

CH3—CH2 —C—O—CH2—CH3

26 Acid Hydrolysis of Esters

In acid hydrolysis • an ester reacts with water to produce a carboxylic acid and an alcohol. • an acid catalyst is required. O  H+ H—C—O—CH2—CH3 + H2O

O  H—C—OH + H—O—CH2—CH3

27 Base Hydrolysis (Saponification)

Base hydrolysis or saponification, • is the reaction of an ester with a strong base. • produces the salt of the carboxylic acid and an alcohol. O || CH3—C—O—CH2—CH3 + NaOH O  – + CH3—C—O Na + HO—CH2—CH3 salt of carboxylic acid alcohol

28 Base Hydrolysis of Fatty Acids Produces Soaps

29 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.

30 Learning Check

Write the organic products when methyl acetate reacts with

A. water and an acid catalyst. O  CH3—C—OH + HO—CH3

B. KOH. O  – + CH3—C—O K + HO—CH3

31 Chapter 13 Carboxylic Acids, Ester, Amines, and Amides 13.4 Amines

32 Amines

Amines

• are derivatives of ammonia, NH3. • contain N attached to one or more alkyl or aromatic groups.

CH CH 3 3 N H 2  

CH3—NH2 CH3—NH CH3—N—CH3

33 Classification of Amines

Amines are classified as primary, secondary, or tertiary. • In a primary (1°) amine, one carbon group is bonded to the nitrogen atom. • A secondary (2°) amine has two carbon groups bonded to the nitrogen atom. • A tertiary (3°) amine has three carbon groups bonded to the nitrogen atom.

H CH3 CH3 | | | CH3—N—H CH3—N—H CH3—N—CH3 1° 2° 3°

34 Models of Amines

The three-dimensional models show the shapes of amine molecules with one or more alkyl groups bonded to the nitrogen atom.

35 Naming Amines

Simple amines • are named as alkylamines. • List the names of the alkyl groups bonded to the N atom in alphabetical order in front of amine.

CH3—CH2—NH2 ethylamine

CH3—NH—CH3 dimethylamine CH3 |

CH3—N—CH2—CH3 ethyldimethylamine

36 Learning Check

Give the common name and classify as primary, secondary, or tertiary.

A. CH3—CH2—CH2—NH2 propylamine, 1°

CH3 |

B. CH3—CH2—N—CH3 ethyldimethylamine, 3°

37 Aromatic Amines

• The amine of benzene is named aniline. • Alkyl groups on the N use the prefix N- with alkyl name.

aniline 3-chloroaniline N-methylaniline

38 Learning Check

Give the common name of each compound.

A. CH3—NH—CH2—CH3 ethylmethylamine

CH3 |

B. CH3—CH2—N—CH2—CH3 diethylmethylamine

C. NH2 aniline

39 Hydrogen Bonding for Amines

The N−H bond • provides hydrogen bonding in 1°and 2° amines, but not in 3° amines. • is not as polar as the O-H bonds in alcohols.

40 Solubility in Water

Amines • with 1-5 carbon atoms are soluble in water. • form hydrogen bonds with the polar O-H bond in water.

41 Learning Check

Consider the following compounds:

1) CH3—CH2—CH2—NH2

2) CH3—CH2—NH—CH3

3) CH3—CH2—CH2—CH3

A. Which compound has the highest boiling point?

1) CH3—CH2—CH2—NH2

B. Which compound is soluble in water?

1) CH3—CH2—CH2—NH2 2) CH3—CH2—NH—CH3

42 Amines React as Bases

Like ammonia, amines are weak bases in water.

+ – NH3 + H2O NH4 + OH ammonium hydroxide

+ – CH3—NH2 + H2O CH3—NH3 + OH methylammonium hydroxide

43 Neutralization forms Amine Salts

An amine salt • forms when an amine is neutralized by acid. • is named by replacing the amine part of the name with ammonium followed by the name of the negative ion. + – CH3—NH2 + HCl CH3—NH3 Cl methylamine methylammonium chloride

44 Properties of Amine Salts

Amine salts are • solids at room temperature. • soluble in water and body fluids. • the form used for drugs.

45 Alkaloids

Alkaloids are • physiologically active nitrogen-containing compounds. • obtained from plants. • used as anesthetics, antidepressants, and in stimulants such as caffeine. • often addictive.

46 Cocaine

Cocaine is • sold illegally as the amine salt. • reacted with NaOH to produce the free amine form known as “crack.”

47 Caffeine

Caffeine • is a stimulant of the central nervous system. • is found in coffee beans, tea, chocolate, and soft drinks.

48 Nicotine

Nicotine • increases the adrenaline level in the blood. • causes addiction to tobacco.

C H 3

49 Morphine and Codeine

Morphine and codeine are • alkaloids. • obtained from the oriental poppy plant. • used as painkillers. • modified to make heroin.

50 Learning Check

Write the structural formula for

A methylpropylamine CH3–CH2–CH2–NH–CH3

B. 2-chloroaniline NH 2 Cl

51 Chapter 13 Carboxylic Acids, Esters, Amines, and Amides

13.5 Amides

52 Amides

In amides,

• an amino group(–NH2) replaces the –OH group of carboxylic acids. O O || || CH3—C—OH CH3—C—NH2

53 Aromatic Amide

The aromatic amine is benzamide.

NH2

benzamide

54 Preparation of Amides

Amides are produced • by reacting a carboxylic acid with ammonia or an amine (1 or 2 ). • using heat.

O O  Heat  CH3—C—OH + NH3 CH3—C—NH2 + H2O

O O  Heat  CH3—C—OH + CH3—NH2 CH3—C—NH—CH3 + H2O

55 Naming Amides

Amides are named as alkanamides. • IUPAC replaces –oic acid ending with –amide. • Common names replace -ic acid ending with –amide. O  Methanamide (IUPAC)

H—C—NH2 Formamide (common)

O  Propanamide (IUPAC)

CH3—CH2—C—NH2 Propionamide (common)

56 Naming Amides with N Groups

An alkyl group bonded to the N atom is named as N-alkyl in front of the amide name. O H  │

CH3 —C—N—CH3 N-methylethanamide (IUPAC) N-methylacetamide (common) O H  │

CH3—CH2 —C—N—CH2—CH3 N-ethylpropanamide (IUPAC) N-ethylpropionamide (common)

57 Learning Check

Give the IUPAC and common names for the following:

O 

A. CH3–CH2–CH2–C–NH2 butanamide; butryamide

O H  │

B. CH3–C–N–CH2–CH3

N-ethylethanamide; N-ethylacetamide

58 Learning Check

Draw the structures of:

A. pentanamide O 

CH3–CH2–CH2–CH2–C–NH2

B. N-methylbutyramide O 

CH3–CH2–CH2–C–NH–CH3

59 Some Amides in Health and Medicine

• Urea is the end product of protein metabolism. • Saccharin is an artificial sweetener. • Some amides such as phenobarbital, Nembutal and Seconal are barbiturates. • Acetaminophen is used to reduce fever and pain.

60 Some Amides in Health and Medicine

61 Physical Properties of Amides

Amides

• that are primary (−NH2) or secondary (−NH−) form hydrogen bonds. • that are primary have higher melting points than secondary. • that are tertiary (no H on N) do not form hydrogen bonds and have lower melting points. • all form hydrogen bonds with water. • with 1-5 carbon atoms are soluble in water.

62 Hydrogen Bonding of Amides

O || CH3—C—N—H | H Hydrogen bonding occurs between primary amides. O || CH3—C—N—H | H

63 Hydrolysis of Amides

Amides undergo

• Acid hydrolysis to produce a carboxylic acid and an ammonium salt.

• Base hydrolysis to produce the salt of a carboxylic acid and an amine or ammonia.

64 Hydrolysis Reactions

acid hydrolysis O || + – O CH3—C—OH + NH4 Cl || HCl + H2O CH3—C—NH2

NaOH O || – + CH3—C—O Na + NH3

base hydrolysis

65 Learning Check

Write the products of the hydrolysis of N-ethylpropanamide with NaOH.

O  – + CH3—CH2—C—O Na + CH3—CH2—NH2