Chapter 14 - faculty at Chemeketa

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Transcript Chapter 14 - faculty at Chemeketa

Chapter 14 Carboxylic Acids,
Esters, Amines, and Amides
14.1
Carboxylic Acids
1
A poem by Ogden Nash
The ant has made himself illustrious
Through constant industry industrious
So what?
Would you be calm and placid
If you were full of formic acid?
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
3
IUPAC Names
In the IUPAC names of carboxylic acids
• the -e in the alkane name is replaced with -oic acid.
CH4
Methane
CH3—CH3 Ethane
HCOOH
Methanoic acid
CH3—COOH Ethanoic acid
• substituents are numbered from the carboxyl carbon 1.
O
CH3
CH3
4
CH
3
CH2
2
C
1
OH
3-methylbutanoic acid
4
Names and Sources of Some
Carboxylic Acids
5
Common Names for Acids
HCOOH
CH3COOH
CH3CH2COOH
CH3(CH2)2COOH
CH3(CH2)3COOH
CH3(CH2)4COOH
CH3(CH2)5COOH
CH3(CH2)6COOH
Formic
Acetic
Propionic
Butyric
Valeric
Caproic
Enanthic
Caprylic
http://en.wikipedia.org/wiki/Carboxylic_acid
Formica (ant)
Acetum (sour)
Pro (first) + Pion (fat)
Butyrum (butter)
Valere (strong)
Caper (goat)
Vine (wine)
Caper (goat)
Common Carboxylic Acids
methanoic acid (formic acid)
O
H
C
OH
ethanoic acid (acetic acid)
O
CH3
C
OH
7
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8
Aromatic Carboxylic Acids
Benzoic acid
• is the aromatic carboxylic acid.
• locates substituents by numbering the ring from
carbon 1 in the carboxyl group.
3,4-Dichlorobenzoic Acid
Benzoic Acid
Para-Aminobenzoic Acid
9
Chapter 14 Carboxylic Acids,
Esters, Amines, and Amides
14.2
Properties of Carboxylic Acids
10
Polarity of Carboxylic Acids
Carboxylic acids
• are strongly polar.
• have two polar groups:
hydroxyl (−OH) and
carbonyl (C=O).
11
Comparison of Boiling Points
Compound
Molar Mass
Boiling Point
O
CH3
CH3
CH2
CH2
C
CH2
H
OH
58
49 °C
60
97 °C
60
118 °C
O
CH3
C
OH
12
Solubility in Water
Carboxylic acids:
• form hydrogen bonds
with many water
molecules.
Water molecules
• with 1-4 carbon
atoms are very
soluble in water.
13
Acidity of Carboxylic Acids
Carboxylic acids
• are weak acids.
• ionize in water to produce carboxylate ions
and hydronium ions.
O
CH3
C
O
OH
+
H2O
CH3
C
O-
+
H3O+
14
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.
15
Monosodium glutamate (MSG, also known as sodium glutamate)
16
Chapter 14 Carboxylic Acids,
Esters, Amines, and Amides
14.3
Esters
17
Esters
In an ester, the H in the carboxyl group is replaced
with an alkyl group.
O
CH3
C
O
CH3
ester group
18
Esterification
Esterification is the reaction of
• a carboxylic acid and alcohol in the presence of an
acid catalyst to produce an ester.
O
CH3
C
OH
+
H
O
O
CH2
CH2
CH3
H+
O
CH3
C
CH3
+
H2O
Ethyl acetate (an ester)
19
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.
O
C OH
O
O C CH3
O
C O CH3
OH
20
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
21
Naming Esters
Esters are named
• with the alkyl group of the alcohol,
• and the salt (-ate) of the carboxylic acid
From
methanol
(methyl
alcohol)
From ethanoic
acid (acetic
acid)
Methyl ethanoate
(methyl acetate)
22
Esters in Plants
Esters give pleasant fragrances and flavors to many
fruits and flowers.
23
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
24
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
25
Base Hydrolysis of Fatty Acids
Produces Soaps
26
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.
27
Chapter 14 Carboxylic Acids,
Esters, Amines, and Amides
14.4
Amines
28
Amines
Amines
• are derivatives of ammonia, NH3.
• contain N attached to one or more alkyl or
aromatic groups.
CH3
CH3
NH2
CH3
NH
NH2
CH3
CH3
N
CH3
29
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
CH3
|
CH3—N—CH2—CH3
Dimethylamine
Ethyldimethylamine
30
Do You
?
N
Know
What
Aromatic Amines
• The amine of benzene is named aniline.
• Alkyl groups on the N use the prefix N- with alkyl name.
NH2
NH2
NH CH3
Cl
aniline
3-chloroaniline
meta-chloroaniline
N-methylaniline
32
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.
33
Solubility in Water
Amines
• with 1-6 carbon atoms are soluble in water.
• form hydrogen bonds with the polar O-H bond in water.
Copyright © 2009 by Pearson Education, Inc.
34
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
35
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
36
Properties of Amine Salts
Amine salts are
• solids at room temperature.
• soluble in water and body fluids.
• the form used for drugs.
Ephedrine hydrochloride
Ephedrine HCl
Sudafed
Diphenhydramine hydrochloride
Diphenhydramine HCl
Benadryl
37
Alkaloids
Alkaloids are
• physiologically active nitrogencontaining compounds.
• obtained from plants.
• used as anesthetics,
antidepressants, and in stimulants
such as caffeine.
• often addictive.
38
Cocaine
Cocaine (from coca leaves ) is
• sold illegally as the amine salt.
• reacted with NaOH to produce the free
amine form known as “crack.”
Cocaine hydrochloride
Cocaine (free base)
39
Caffeine
Caffeine
• is a stimulant of the
central nervous system.
• is found in coffee beans,
tea, chocolate, and soft
drinks.
Caffeine
40
Nicotine
Nicotine
• increases the adrenaline level in the blood.
• causes addiction to tobacco.
N
CH 3
41
Morphine and Codeine
Morphine and codeine are
• alkaloids.
• obtained from the
oriental poppy plant.
• used as painkillers.
• modified to make heroin.
Morphine
Codeine
42
Chapter 14 Carboxylic Acids,
Esters, Amines, and Amides
14.5
Amides
43
Amides
In amides,
• an amino group(–NH2) replaces the –OH group of
carboxylic acids.
O
CH3
C
O
OH
CH3
C
NH2
44
Aromatic Amide
The aromatic amine is benzamide.
O
C
NH2
Benzamide
45
Some Amides in Health and
Medicine
• Urea is the end product of protein metabolism.
• Saccharin is an artificial sweetener.
• Some amides such as phenobarbital, NembutalTM
and SeconalTM are barbiturates.
• Acetaminophen is used to reduce fever and pain.
46
Some Amides in Health and
Medicine
47
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.
48
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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