chapter 13 carboxylic acids, esters, amines, and … the iupac names of carboxylic acids: •...
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Chapter 13 Carboxylic Acids,
Esters, Amines, and Amides
13.1
Carboxylic Acids
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
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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
Carboxylic Acids
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Models of Carboxylic Acids
The three-dimensional models show the geometry of
atoms in carboxylic acid molecules.
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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
3-methylbutanoic acid
IUPAC Names
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Names and Sources of Some
Carboxylic Acids
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Common Carboxylic Acids
Methanoic acid (formic acid)
O
║
H─C─OH
ethanoic acid (acetic acid)
O
║
CH3─C─OH
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Aromatic Carboxylic Acids
Benzoic acid
• is the aromatic
carboxylic acid.
• locates substituents
by numbering the
ring from carbon 1 in
the carboxyl group.
OHC
O
OHC
O
OHC
O
ClNH2
3-chlorobenzoic acid 4-aminobenzoic acid
benzoic acid
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Learning Check
Give the IUPAC names of each compound.
A. CH3─CH2─COOH
CH3
|
B. CH3─CH─CH2─COOH
C.
OHC
O
Br
propanoic acid
3-methylbutanoic acid
3-bromobenzoic acid
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13.2 Properties of Carboxylic Acids
Chapter 13 Carboxylic Acids,
Esters, Amines and Amides
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
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Polarity of Carboxylic Acids
Carboxylic acids
• are strongly polar.
• have two polar groups:
hydroxyl (−OH) and
carbonyl (C=O).
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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.
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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
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Solubility in Water
Carboxylic acids:
• form hydrogen bonds
with many water
molecules.
• with 1-4 carbon
atoms are very
soluble in water.
Water molecules
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Boiling Points and Solubility
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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+
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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.
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Learning Check
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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
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Chapter 13 Carboxylic Acids,
Esters, Amines, and Amides
13.3
Esters
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
19
Esters
In an ester, the H in the carboxyl group is replaced
with an alkyl group.
O
CH3 — C—O —CH3
ester group
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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)
Esterification
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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
Learning Check
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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.
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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
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Esters in Plants
Esters give flowers and fruits their pleasant fragrances
and flavors.
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
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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)
Learning Check
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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
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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
Acid Hydrolysis of Esters
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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
Base Hydrolysis (Saponification)
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Base Hydrolysis of Fatty Acids
Produces Soaps
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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.
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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
Learning Check
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Chapter 13 Carboxylic Acids,
Ester, Amines, and Amides
13.4
Amines
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Amines
Amines
• are derivatives of ammonia, NH3.
• contain N attached to one or more alkyl or
aromatic groups.
CH3 CH3
CH3—NH2 CH3—NH CH3—N—CH3
N H 2
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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°
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Models of Amines
The three-dimensional models show the shapes of amine molecules with one or more alkyl groups bonded to the nitrogen atom.
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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
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Give the common name and classify as primary,
secondary, or tertiary.
A. CH3—CH2—CH2—NH2
CH3
|
B. CH3—CH2—N—CH3
Learning Check
propylamine, 1°
ethyldimethylamine, 3°
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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
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Learning Check
Give the common name of each compound.
A. CH3—NH—CH2—CH3
CH3
|
B. CH3—CH2—N—CH2—CH3
C. NH2
ethylmethylamine
diethylmethylamine
aniline
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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.
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Solubility in Water
Amines
• with 1-5 carbon atoms are soluble in water.
• form hydrogen bonds with the polar O-H bond in water.
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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
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Like ammonia, amines are weak bases in water.
NH3 + H2O NH4+ + OH–
ammonium hydroxide
CH3—NH2 + H2O CH3—NH3+ + OH–
methylammonium hydroxide
Amines React as Bases
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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
Neutralization forms Amine Salts
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Properties of Amine Salts
Amine salts are
• solids at room temperature.
• soluble in water and body fluids.
• the form used for drugs.
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Alkaloids
Alkaloids are
• physiologically active
nitrogen-containing
compounds.
• obtained from plants.
• used as anesthetics,
antidepressants, and in
stimulants such as
caffeine.
• often addictive.
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Cocaine
Cocaine is
• sold illegally as the amine salt.
• reacted with NaOH to produce the free amine form
known as “crack.”
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Caffeine
• is a stimulant of the central nervous system.
• is found in coffee beans, tea, chocolate, and soft drinks.
Caffeine
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Nicotine
Nicotine
• increases the adrenaline level in the blood.
• causes addiction to tobacco.
N
C H 3
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Morphine and Codeine
Morphine and codeine are
• alkaloids.
• obtained from the
oriental poppy plant.
• used as painkillers.
• modified to make heroin.
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Learning Check
Write the structural formula for
A methylpropylamine
B. 2-chloroaniline
CH3–CH2–CH2–NH–CH3
NH2
Cl
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13.5
Amides
Chapter 13 Carboxylic Acids,
Esters, Amines, and Amides
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
53
In amides,
• an amino group(–NH2) replaces the –OH group of
carboxylic acids.
Amides
Copyright © 2005 by Pearson
Education, Inc.
Publishing as Benjamin
Cummings
O || CH3—C—OH
O || CH3—C—NH2
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Aromatic Amide
The aromatic amine is benzamide.
benzamide
O
CNH2
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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
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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)
Naming Amides
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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)
Naming Amides with N Groups
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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
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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
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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.
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Some Amides in Health and
Medicine
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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.
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Hydrogen Bonding of Amides
O || CH3—C—N—H | H Hydrogen bonding occurs between primary amides. O || CH3—C—N—H | H
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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.
Hydrolysis of Amides
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acid hydrolysis O || O CH3—C—OH + NH4
+Cl– || HCl + H2O CH3—C—NH2
NaOH O || CH3—C—O– Na+ + NH3
base hydrolysis
Hydrolysis Reactions
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Write the products of the hydrolysis of
N-ethylpropanamide with NaOH.
O CH3—CH2—C—O– Na+ + CH3—CH2—NH2
Learning Check