Download Chapter Three

13 Hydrocarbon Derivatives II
Compounds with carbon-oxygen
double bonds
Aldehydes
Ketones
Carboxylic Acids
Esters
Amides
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3–1
13 Hydrocarbon Derivatives II
The carbon-oxygen double bond is called a
carbonyl group, and occurs in different
functional groups.
R1
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O
C
R2
3–2
13 Hydrocarbon Derivatives II
The carbon of the carbonyl group has trigonal
planar electronic and molecular geometry.
R1
O
C
R2
The carbonyl group is polar.
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3–3
13.2 Naming Aldehydes
Aldehydes have at least one hydrogen
substituent on the carbonyl group.
The other substituent can be any
hydrocarbon.
H
O
C
H
H3C
H3C
N
H3C
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O
C
H
O
C
H
3–4
13.2 Naming Aldehydes
1.
2.
3.
4.
Suffix is “-al”
Find longest chain that bears carbonyl
Number carbon chain so carbonyl is #1
Locate and name any other substituents
Final “e” on name of hydrocarbon is
dropped
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3–5
13.2 Naming Aldehydes
Common names are frequently used too.
H
IUPAC
O
C
H
methanal
Common formaldehyde
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H3C
O
C
H
H3C CH2
O
C
H
ethanal
propanal
acetaldehyde
propionaldehyde
3–6
13.2 Naming Aldehydes
Aromatic aldehydes are named as
benzaldehydes.
O
C
H
Cl
O
C
H
Cl
Benzaldehyde
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2,4-dichlorobenzaldehyde
3–7
13.4 Naming Ketones
Ketones have two hydrocarbon substituents on the carbonyl group. The
carbonyl group can be in a ring.
H3C
O
C
O
C
O
C
CH3
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3–8
13.4 Naming Ketones
1.
2.
3.
4.
Suffix is “-one”
Find longest chain that bears carbonyl
Number carbon chain so carbon bearing
C=O has lowest possible number;
it cannot be #1
Locate and name any other substituents
Final “e” on name of hydrocarbon is
dropped
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3–9
13.4 Naming Ketones
Common names are frequently used.
They are formed by naming the
alkyl substituents on the carbonyl,
usually in alphabetical order.
H3C
IUPAC
Common
O
C
CH3
H3C
O
C
CH2 CH3
2-propanone
2-butanone
acetone
methyl ethyl ketone (MEK)
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3–10
13.4 Naming Ketones
Compounds with carbonyl groups in rings
are named as cycloalkanones. The
carbonyl carbon is #1; this locant is
understood and not given.
O
CH3
C
CH3
O
C
Cl
cyclohexanone
4-chloro-2,2-dimethylcyclopentanone
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3–11
13.4 Naming Ketones
Aromatic ketones are named as phenones,
or as ketones with phenyl and alkyl
substituents.
O
C
O
C
CH3
benzophenone
acetophenone
diphenyl ketone
methyl phenyl ketone
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3–12
13.4 Naming Ketones
Acetyl groups are carbonyl groups bonded
to methyl groups. “Acet-” and “aceto-”
appear often in names of carbonyl
compounds.
H3C
O
C
acetyl
group
H3C
O
C
H
acetaldehyde
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H3C
O
C
CH3
acetone
H3C
O
C
OH
acetic
acid
3–13
13.3,5 Properties of
Aldehydes and Ketones
Aldehydes and ketones have similar properties and undergo similar reactions.
These will be considered together.
Aldehydes and ketones are polar, but are
not hydrogen bond donors. Their boiling
points are intermediate between alcohols
and alkanes/ethers.
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3–14
13.3,5 Properties of
Aldehydes and Ketones
Aldehydes and ketones have
similar prop-erties and
undergo similar reactions.
These will be considered
together.
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3–15
13.3,5 Properties
Aldehydes and ketones can act as hydrogen
bond acceptors. Small compounds are
appreciably soluble in water.
C O
H O
H
Formaldehyde, acetaldehyde, and acetone
are completely soluble in water.
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3–16
13.3,5 Reactions
Aldehydes are generally more reactive than
ketones, and can undergo some reactions
that ketones do not. There are more similarities than differences.
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3–17
13.3,5 Reactions
Aldehydes are easily oxidized to
carboxylic acids.
O
C
H
benzaldehyde,
viscous liquid,
almond fragrance
O2
O
C
OH
benzoic acid,
white solid,
no fragrance
Ketones are not easily oxidized.
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3–18
13.3,5 Reactions
Tollens’ test is an oxidation of aldehydes by
Ag1+, which is reduced to silver metal.
R
O
C
H
+
Ag1+
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NH3
H2O
R
O
C
+ Ag(metal)
OH
3–19
13.3,5 Reactions
Aldehydes and ketones can be
reduced to alcohols.
R
R1
O
C
O
C
[H2]
H
[H2]
R2
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OH
H C
H
R
1 alcohol
OH
H C
R2
R1
2 alcohol
3–20
13.3,5 Reactions
Catalytic hydrogenation works, but more often
NaBH4 or LiAlH4 is used. These compounds
behave as sources of hydride anion, H1–.
Na
H
H B H
H
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Li
H
H Al H
H
3–21
13.3,5 Reactions
Hydration is addition of water across the
C=O bond. It is similar to addition
across a C=C bond.
R1
O
C
H
+
H2O
OH
R1 C OH
H
hydrated aldehyde
Aldehydes hydrate more readily than
ketones. Formaldehyde hydrates
completely. Formalin is a solution of
hydrated formaldehyde.
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3–22
13.3,5 Reactions
Alcohols can add across a C=O bond. The
product is called a hemiacetal.
R1
O
C
H
+
HO R2
OH
R1 C O R
2
H
hemiacetal
Ketones undergo the same reaction, but
less readily. The product is sometimes
called a hemiketal. We’ll call both types
hemiacetals.
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3–23
13.3,5 Reactions
Hemiacetals have ether and hydroxyl groups
on the same carbon.
R1
O
C
R3
R2
+
R3OH
O
O C
H R1 R2
R2 can be H
The two structures are in equilibrium, and the
hemiacetal can be difficult to isolate.
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3–24
13.3,5 Reactions
Carbonyl compounds with hydroxyl groups
three or four carbons away readily form
cyclic hemiacetals.
R1
R1
O
C
O
C
R1 OH
O
CH2 CH2 CH2 O H
R1
OH
O
CH2 CH2 CH2 CH2 O H
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3–25
13.3,5 Reactions
In the presence of excess alcohol, acetals
form. Acetals of ketones may be called
ketals.
R1
O
C
R3
R2
+
2 R3OH
H3O1+
catalyst
heat
 H2O
O
+ H2O
O C
R3 R1 R2
R2 can be H
The equilibrium is not favorable for the reaction. Catalysis speeds it up, and water
removal drive it to completion.
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3–26
13.3,5 Reactions
Acetals have two ether groups on the
same carbon. Like ethers, they
are not very reactive.
R3
O
O C
R3 R1 R2
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3–27
13.3,5 Reactions
Acetals can be converted back to the
parent aldehydes or ketones with
water and an acid catalyst.
R3
O
+ H2O
O C
R3 R1 R2
H3O1+ catalyst
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R1
O
C
R2
+
2 R3OH
3–28
13.3,5 Reactions
Diols give cyclic acetals.
O
C
+
HO CH2 CH2 OH
ethylene glycol
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H3O1+
O
O
heat
 H2O
3–29
Common Aldehydes
Formaldehyde, the simplest aldehyde, is used
for sterilizing apparatus and as an embalming fluid.
H
O
C
H
+
formaldehyde
H2O
HO OH
C
H
H
formalin
It is also a component of synthetic resins, e.g.
phenol-formaldehyde (Bakelite), and
melamine-formaldehyde (Formica).
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3–30
Common Aldehydes
Aldehydes are components of flavors and odors.
O
C
H
HO
benzaldehyde,
almond oil
H
C
C
H
O
C
H3C O
vanillin
H3C
H
cinnamaldehyde
Copyright © Houghton Mifflin Company. All rights reserved.
O
C
H
CH
H3C
O
C
H
cuminaldehyde
3–31
Common Ketones
Simple ketones are solvents and degreasers.
H3C
O
C
CH3
acetone
H3C
O
C
CH2 CH3
methyl ethyl ketone (MEK)
Simple aldehydes are too reactive and
toxic to be used as solvents.
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3–32
Common Ketones
Aromatic ketones are used as photoinitiators
for resin that cure in ultraviolet light, such
as those in dental sealants.
O
C
benzophenone
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O
OH
C
hydroxycyclohexylphenyl ketone
3–33
Common Ketones
Ketones are functional groups in some
steroid hormones.
OH
O
O
O
OH
O
O
cortosone
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progesterone
3–34
13.6 Carboxylic Acids
Carboxylic acids have a carboxyl group (COOH)
on a hydrocarbon chain; R–COOH
R
O
C
OH
The carboxyl group has a hydroxyl group on a
carbonyl carbon.
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3–35
13.6 Naming Carboxylic Acids
1.
2.
3.
4.
Suffix is “-oic acid”
Find longest chain that bears –COOH
Number carbon chain so –COOH is #1
Locate and name any other substituents
Final “e” on name of hydrocarbon is
dropped
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3–36
13.6 Naming Carboxylic Acids
Simple carboxylic acids are often known by
common names.
H
O
C
H3C
OH
O
C
OH
IUPAC
methanoic acid
ethanoic acid
Common
formic acid
acetic acid
H3C CH2 CH2
O
C
IUPAC
butanoic acid
Common
butyric acid
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OH
3–37
13.6 Naming Carboxylic Acids
Aromatic carboxylic acids are named as
derivatives of benzoic acid.
O
C
OH
O
C
OH
OH
benzoic acid
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2-hydroxybenzoic acid
a.k.a. salicylic acid
3–38
13.6 Naming Carboxylic Acids
Aromatic dicarboxylic acids are named as
phthalic acids, because the ortho isomer
was originally made from naphthalene.
O
C
OH
OH
C
O
phthalic acid,
ortho-phthalic acid
HO
O
C
O
C
O
C
OH
isophthalic acid,
meta-phthalic acid
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OH
HO
C
O
terephthalic acid,
para-phthalic acid
3–39
13.7 Properties of Carboxylic Acids
Carboxylic acids with up to nine
carbon atoms are liquids with
pungent odors.
Acetic acid, in vinegar, is a good
example. “Acet” comes from
“vinum acetum,” sour wine.
Larger molecules are waxy solids, as
are aromatic carboxylic acids.
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3–40
13.7 Properties of Carboxylic Acids
O
Carboxylic
acids
to nine
H3C C
Aceticwith
acid upVinegar
carbon
OH atoms are liquids with
pungent odors.
H3C-CH2-CH2
O
C
OH
Butyric acid
Rancid butter
H3C-(CH2)4
O
C
OH
Caproic acid
Goat cheese
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3–41
13.7 Properties of Carboxylic Acids
Carboxylic acids are polar, and form dimers
through hydrogen bonding. They have
have quite high melting and boiling points.
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3–42
13.7
Properties
Carboxylic
Acids
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3–43
13.7 Properties of Carboxylic Acids
Carboxylic acids are
slightly more soluble in water than
alcohols with the
same number of
carbons.
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3–44
13.7 Acidity of Carboxylic Acids
O
R C
O H
+
H
O
H
O
R C
O
Carboxylate
anion
H
+
O
H
H
Hydronium
cation
Carboxylic acids are proton donors.
When R is alkyl, Keq is about 10–5.
Keq = [H3O1+][RCOO1–]
[RCOOH][H2O]
Less than 5% of the molecules are ionized.
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3–45
13.7 Acidity of Carboxylic Acids
H
O
H
H
1+
H
O
H
Hydronium
cation
H
CH3
O
C
O
1
CH3
O
C
O
Acetate
anion
In organic chemistry, we often show ionic
charges on specific atoms. These are
called “formal charges.”
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3–46
13.7 Acidity of Carboxylic Acids
O
R C
O H
+
O H
Hydroxide
anion
O
R C
O
+
H
O
H
Carboxylate
anion
In strong base, ionization is complete.
O
R C
O
O
R C
O
Carboxylate anions are stabilized by resonance.
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3–47
13.7 Acidity of Carboxylic Acids
O
R C
O
H
+
O
H
H
O
R C
O H
+
H
O
H
In strong acid, the carboxylate is
completely protonated.
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3–48
13.7 Naming Carboxylate Salts
O
CH3 C
O
O
CH3 CH2 CH2 C
O
acetate
butanoate
(butyrate)
O
C
O
benzoate
Carboxylate anions are named as the “-ate”
anion of the conjugate acid.
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3–49
13.7 Naming Carboxylate Salts
O
CH3 C
O
O
C
O
Na
Sodium acetate
O
C
K1+
Potassium benzoate
O
O
Cu2+
C
O
Copper (II) phthalate
Ionic compounds are also called “salts.”
Those that contain carboxylate anions
are named with the cation (usually a
metal) followed by the name of the
carboxylate.
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3–50
13.7 Reactions of Carboxylic Acids
Acid-base reactions:
Carboxylic acids equilibrate with their
conjugate bases in water.
RCOOH + H2O  RCOO1– + H3O1+
Carboxylic acids deprotonate to carboxylate
salts in strong bases.
RCOOH + OH1–  RCOO1– + H2O
Carboxylate anions are protonated in strong
acids.
RCOO1– + H3O1+  RCOOH + H2O
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3–51
13.7 Reactions of Carboxylic Acids
Condensation reactions:
Condensation reactions are reactions in which
two molecules combine into one, with the
expulsion of a small molecule such as water.
The dehydration of alcohols to form ethers is
a condensation reaction.
RCH2OH
+ HOCH2R
H2SO4
140 C
RCH2OCH2R
Copyright © Houghton Mifflin Company. All rights reserved.
+
H2O
3–52
13.7 Reactions of Carboxylic Acids
Esters are produced by the condensation of a
carboxylic acid and an alcohol.
O
C
+
OH
HO CH3
H1+
O
C
+
O CH3
H2O
Keq is often near 1. In the classic Fischer
Esterification, H2SO4 is the catalyst.
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3–53
13.7 Reactions of Carboxylic Acids
Lactones are cyclic esters. They are
formed by intramolecular condensations of hydroxy acids.
O
HO CH2 CH2 CH2 C
OH
O
HO CH2 CH2 CH2 CH2 C
OH
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catalyst
C O
+ H2O
O
-butyrolactone
catalyst
+ H2O
C O
O
-valerolactone
3–54
13.7 Reactions of Carboxylic Acids
Amides are produced by the condensation of a
carboxylic acid and ammonia or an amine.
O
+
C
OH
CH3
HN
CH3
H1+
heat
O
+
C
N CH3
CH3
H2O
The amine must have at least one hydrogen, or
water cannot form.
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3–55
13.7 Reactions of Carboxylic Acids
Direct formation of amides from carboxylic acids
and amines is complicated by the acid-base
reaction between reactants.
O
+
C
O H
CH3
N H
CH3
mild
conditions
O
C
O
CH3
+ H N H
CH3
“Heat” means > 200C (>400F) to decompose
the salt and form the amide.
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3–56
Important Carboxylic Acids
O
Formic acid, simplest carboxylic
H Direct
C
acid,of
used
in antimicrobials
formation
amides
from and
OH
carboxylic leather
acidstanning
and amines
Ois complicated
Aceticby
acid,
the acidmost common
the
carboxylic acid, found in vinegar
H3C C base reaction
between
and
widely
used in industry.
OH
H
reactants.
H
O
acid, (>400F)
simplest unsaturated
“Heat”
means Acrylic
> 200C
C C
carboxylic
acid,
used
to make
to
decompose
the
salt
and
C
OH
water-soluble polymers
H form the amide.
H3C
O
C C
H C
OH
H
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Methacrylic acid, used to make
esters and polymeric derivatives
3–57
Important Carboxylic Acids
O
Benzoic
acid, simplest
aromatic
Direct
formation
of
amides
from
C
carboxylic acid, used as a food
carboxylic
acids
and amines
OH
preservative
and industrial feed.
O
C
HO
is complicated by the acidO
base reaction between
C
o-Phthalic acid, generally used
reactants.
OH
as its anhydride, in plasticisers
OHmeans > 200C
and dyes(>400F)
“Heat”
C
to decompose the salt and
O
form the amide.
O
OH
Copyright © Houghton Mifflin Company. All rights reserved.
Terephthalic acid, used in
polyester plastics and fibers
3–58
Important Carboxylic Acids
O
Direct
formation of amides from
C
Salicylic acid, "willow acid," is an
OH
carboxylicantiinflammatory
acids and amines
and antipyretic;
esters are aspirin and wintergreen
OH is complicated by the acid-
base reaction between
OH O
reactants.Lactic acid, "milk acid," is important
CH3 CH C
in metabolism in its anionic form
“Heat”
means
> 200C (>400F)
OH
to decompose the salt and
O
O form the amide.
Pyruvic acid is a metabolite of glucose
CH3 C
C
OH
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that enters the Citric Acid Cycle. The
name comes from "pyrolysis of grapes."
3–59
O
C
Important Carboxylic Acids
OH
Stearic acid, "typical" saturated fatty acid
Direct formation of amides from O
carboxylic acids and amines OH
complicated
by the acid-fatty acid
Oleic is
acid,
from olives, monounsaturated
base reaction between
O
reactants.
OH
“Heat” means > 200C (>400F)
Linoleic acid, from vegetable oils, polyunsaturated
to decompose
the
salt
and
fatty acid.
Essential in diet;
used
in oil
paints
O
form the amide.
OH
Linolenic acid, from vegetable oils, polyunsaturated
fatty acid. Essential in diet; used in oil paints
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3–60
13.8 Esters
Esters are derivatives of carboxylic acids.
R1
O
C
OR2
They have an alkoxy group (–OR) on a
carbonyl carbon.
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3–61
13.8 Naming Esters
O
C
+ HO CH3
OH
Benzoic acid
Methanol
H1+
O
C
+
O CH3
Methyl benzoate
H2O
Esters are condensation products of alcohols
and carboxylic acids. They are named as
alkyl alkanoates. The alkyl group is derived from the alcohol; the alkanoate is derived from the acid. The -oic acid suffix or
the acid is replaced by -ate.
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3–62
13.8 Naming Esters
O
CH3 C OH + H2O CH2 CH3
O
CH3 C O CH2 CH3 + H2O
Esters
are condensation
products
of alcohols
Ethyl ethanoate,
a.k.a.
Ethanoic
Ethanol
acetate
acid,
a.k.a.
and
carboxylic acids. TheyEthyl
are
named as
Acetic acid
alkyl alkanoates. The alkyl group is derived from the alcohol; the alkanoate is deO
O
rived from the acid. TheCH-oic
acid
suffix
orO
CH3 CH2 C OH + HO CH3
CH
C
O
CH
+
H
3
2
3
2
the
acid
is
replaced
by
-ate.
Propanoic acid
Methanol
Methyl propanoate
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3–63
13.9 Properties of Esters
CH3
O
O
OH
CH3CHCH2CH3 CH3COCH3 CH3CCH2CH3 CH3CHCH2CH3
bp = 28oC
bp = 57oC
O
bp = 80oC
bp = 99oC
O
O
bp = 199oC
bp = 218oC
Esters are polar, but cannot form hydrogen
bonds. They are slightly soluble in water.
Boiling points are somewhat lower than
those of structurally similar ketones.
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3–64
13.9 Properties of Esters
H3C
O
C
O
C
CH3
O CH2 CH2 CH CH3
Isoamyl acetate
Banana scent
O
CH3
OH
Methyl salicylate
Wintergreen scent
Most simple esters are liquids. Many
have fruity or floral fragrances.
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3–65
13.9 Reactions of Esters
Hydrolysis:
The main reaction of esters is hydrolysis
(breaking with water). It is the reverse of
the condensation reaction.
O
C
+
O CH3
Methyl benzoate
H2O
H1+
O
C
+ HO CH3
OH
Benzoic acid
Methanol
Like formation of the ester, Keq is ~1.
Excess water increases the amount
of hydrolyzed product.
Copyright © Houghton Mifflin Company. All rights reserved.
3–66
13.9 Reactions of Esters
Hydrolysis of esters in base is called
saponification, a.k.a. soap-making!
O
+ NaOH
C
O CH3
H2O
O
C
O
Sodium
benzoate
+ Na
+
HO CH3
Methanol
One uses at least an equivalent of OH1–,
and the acid is isolated as its carboxylate salt. Formation of the salt
drives the reaction to completion.
Copyright © Houghton Mifflin Company. All rights reserved.
3–67
13.9 Reactions of Esters
Transesterification:
It is often easier to prepare complex
esters or amides from simple esters
than from the acids.
H3C
O
SnO(C4H9)2
C C
2
+ HO CH2 CH2 OH
H C
O CH3
H
H3C
O
O
CH3
+ 2 CH3OH
C C
C C
H C
O CH2 CH2 O
C H
H
H
Ethylene glycol dimethacrylate
Copyright © Houghton Mifflin Company. All rights reserved.
3–68
13.9 Reactions of Esters
Transesterification:
It is often easier to prepare complex
esters or amides from simple esters
than from the acids.
2
O
+
CH3(CH2)16 C
O CH3
methyl stearate
CH3(CH2)16
H2N CH2 CH2 NH2
heat
ethylene diamine
O
O
C
C (CH2)16CH3 + 2 CH3OH
N CH2 CH2 N
H
H
ethylene bis stearamide
Copyright © Houghton Mifflin Company. All rights reserved.
3–69
Important Esters
O
H3C C
O CH2 CH3
Ethyl acetate, industrial solvent,
found in nail polish remover
Transesterification:
easier to prepare complex
O It is often
O
Acetylsalicylic
acid, Aspirin,
acetate
HO C esters
O C or amides
from
simple
esters
ester of salicylic acid; antiinflammatory
CH3
than from theand
acids.
antipyretic, not as irritating to the
stomach as salicylic acid
O
C
O
CH3
OH
Copyright © Houghton Mifflin Company. All rights reserved.
Methyl salicylate, rubifacient (causes
reddening of skin by dilating capillaries)
for topical pain relief; oil of wintergreen
3–70
Important Esters
O
Transesterification:
CH2 O C R1
It is often easier to prepare
O
complex
estersTriglyceride
or amidesesters,
CH Ofrom
C Rsimple
2
esters
thanlipids
from
important
O acids.
the
CH2 O C R3
Copyright © Houghton Mifflin Company. All rights reserved.
3–71
13.10 Amides
Amides are derivatives of carboxylic acids.
R1
O
C
N
R3
R2
They have an amine group on a carbonyl
carbon. Any of the R’s can be H.
Copyright © Houghton Mifflin Company. All rights reserved.
3–72
13.10 Amides
Amines are classified by the number of carbon
atoms bonded to the nitrogen atom.
R1
O
C
N
H
H
Primary (1)
Copyright © Houghton Mifflin Company. All rights reserved.
R1
O
C
N
H
R2
Secondary (2)
R1
O
C
N
R3
R2
Tertiary (3)
3–73
13.10 Naming Amides
Suffix is “amide”
1. Root is derived from carboxylic acid
2. IUPAC names for secondary and tertiary
amides involve use of the prefix “N-” for
the amine substituents. If the same group
appears twice, use “di-” and prefix.
3. IUPAC names for amides of simple acids
allow the acid’s common name to be
used.
Copyright © Houghton Mifflin Company. All rights reserved.
3–74
13.10 Naming Amides
O
O is “amide”
Suffix
O
C
C
CH2 CH3
C
1. Root
is derived
carboxylic acid
H3C from
N
H
NH2
Methanamide,
Formamide
H
N-ethylethanamide,
N-ethylacetamide
O
CH3 CH2 C
N
H
Copyright © Houghton Mifflin Company. All rights reserved.
CH3
N
CH3
N,N-dimethylbenzamide
2-methylbutanamide
3–75
13.10 Naming Amides
Compounds in which a carbonyl group
is flanked by two nitrogen atoms are
called ureas.
H
N
H
O
C
N
H
H
Urea
Copyright © Houghton Mifflin Company. All rights reserved.
H
N
H
N
O
O
N
N
H
H
Glycouril
3–76
13.10 Naming Amides
Compounds in which carbonyl groups appear
on either side of the nitrogen are called
imides. Cyclic imides are more common
than straight-chain molecules.
O
C
N CH2 CH3
C
O
N-ethylmaleimide,
NEM, used in enzyme
research
Copyright © Houghton Mifflin Company. All rights reserved.
O
C
N H
C
O
Phthalimide
O
C
N B
C
O
N-bromosucci
NBS (Br2 so
3–77
13.11 Properties of Amides
Amides have resonance structures that cause
the nitrogen atom to be trigonal planar, sp2.
R1
O
C
N
H
R2
R1
O
C
N
H
R2
Rotation about the CN bond is restricted.
Copyright © Houghton Mifflin Company. All rights reserved.
3–78
13.11 Properties of Amides
1 and 2 amides have
strong dipoles and
hydrogen bonds.
For 2 amides, the favored conformation
has the H atom opposite the O atom.
The dipole-dipole
forces and hydrogen bonds are quite
strong.
Copyright © Houghton Mifflin Company. All rights reserved.
R1
O
C
R1
N
H
O
C
R2
N
H
R2
3–79
13.11 Properties of Amides
1 and 2 amides have the highest melting
and boiling points of common compounds.
3 amides are usually high-boiling liquids.
R
O
C
OH
R
O
C
N
H
H
R
O
C
N
H
CH3
R
O
C
N
CH3
R=H
BP
MP
101
8
210
3
199
3
153
61
R = CH3
BP
MP
119
17
222
81
206
28
166
20
R = C6H5
BP
MP
249
123
N/A
128
N/A
78
N/A
45
Copyright © Houghton Mifflin Company. All rights reserved.
CH3
3–80
13.11 Properties of Amides
All amides are hydrogen-bond acceptors.
Those with fewer than 6 carbons are
freely soluble with water.
Copyright © Houghton Mifflin Company. All rights reserved.
3–81
13.11 Reactions of Amides
Hydrolysis:
The main reaction of amides is hydrolysis.
The reaction always requires acid or base.
R1
O
C
R2 + H O
2
N
R3
Copyright © Houghton Mifflin Company. All rights reserved.
R1
O
C
H
+
OH
N
R3
R2
slow,
Keq << 1
3–82
13.11 Reactions of Amides
Formation of the ammonium cation in acid or
the carboxylate anion in base drives the
equilibrium to the right.
R1
R1
O
C
O
C
N
R3
N
R3
R2
R2
+
H3O1+
+ H2O
+ OH1 + H2O
Copyright © Houghton Mifflin Company. All rights reserved.
R1
R1
O
C
O
C
H
OH
+
H N
R3
H
+
O
R2
N
R3
R2
3–83
Important Amides
Simple amides: various small molecules
H
O
C
O
C
H
N
H
CH3
N
CH3
N CH3
O
C
N
H
H
Copyright © Houghton Mifflin Company. All rights reserved.
Dimethyl formamide, DMF
high-boiling polar solvent
N-methylpyrrolidone, NMP,
high-boiling polar solvent
Urea, metabolite of amino
acids, fertilizer
3–84
Important Amides
-lactam antibiotics:
Penicillins, cephalosporins, and related
antibiotics contain the -lactam group.
-lactam
C N
O
R
H
C
O
H
N
H
R1
H
S
O
CH3
O
C N
O
N
CH3
C OH
Penicillin
Copyright © Houghton Mifflin Company. All rights reserved.
H
S
N
R2
O
O
OH
Cephalosporin
3–85
Important Amides
Barbiturates:
Barbituric acid is the parent compound for
many central nervous system depressants.
They are used as sedatives and anesthetics.
O
O
H
N
N
O
H
O
Barbituric Acid
Copyright © Houghton Mifflin Company. All rights reserved.
H
N
N
H
O
O
CH3CH2 C6H5
Phenobarbital
3–86
13.12 Condensation Polymers
Condensation reactions between polyfunctional
carboxylic acids and alcohols or amines
produce a wide variety of polymers. They
are called condensation polymers or stepgrowth polymers because of how they form.
Polymers formed from alkenes are called
chain-growth polymers or addition polymers.
Copyright © Houghton Mifflin Company. All rights reserved.
3–87
13.12 Condensation Polymers
Polyesters are formed in reactions between
diacids and diols.
Polyamides are formed in reactions between
diacids and diamines.
Copyright © Houghton Mifflin Company. All rights reserved.
3–88
13.12 Condensation Polymers
O
C
Polyesters are
between
OH formed in reactions
catalyst
+ HO CH2 CH2 OH
 H2O
HO diacids and diols.
C
ethylene
glycol
O
terephthalic acid
Polyamides are formed in reactions between
diacids and diamines.
O
C
HO
O CH2 CH2 O
C
O
O
C
n
C
O
O CH2 CH2 OH
Poly(ethylene terephthalate), PETE
Copyright © Houghton Mifflin Company. All rights reserved.
3–89
Important Polyesters
O
O
Polyethylene terephthalate,
PETE, "polyester"
in plastics
Polyesters
formed
in reactions
between
C
Care
O CH
2 CH2
and fiber, Dacron
n
diacids and diols.
CH3
methacrylate),
Polyamides
reactions
between
CH2 are
C formed inPoly(methyl
PMMA, polymer used as
C diamines. glass, Lucite, Plexiglas
diacids
and
H3C O
O n
CH3
C
CH3
O
O C O
Copyright © Houghton Mifflin Company. All rights reserved.
n
Polycarbonate, polymer
used as glass, very high
impact resistance
3–90
13.12 Condensation Polymers
HO
O
C
(CH2)4
O
C
+
OH
Adipic acid
HO
O
C
H2N (CH2)6 NH2
285
 H2O
Hexane Diamine
(CH2)4
O
C
N
H
(CH2)6
N
H
O
C
(CH2)4
n
O
C
N
H
(CH2)6
N
H
H
Nylon 6,6
Synthetic and natural polyamides are important.
Nylon 6,6 was developed by Wallace Carothers
of DuPont as a silk replacement in 1935.
Copyright © Houghton Mifflin Company. All rights reserved.
3–91
13.12 Condensation Polymers
In the “nylon rope trick” polymer forms at the
interface of a water solution of hexane diamine and an organic solution of adipoyl
chloride (adipic acid on steroids!).
Copyright © Houghton Mifflin Company. All rights reserved.
3–92
13.12 Condensation Polymers
Nylon 6 was developed in Germany. It is made
by ring-opening, rather than condensation.
O
C
N
H
260C
N2
O
C
(CH2)5
H
N
C
O
(CH2)5
N
H n
Caprolactam
Nylons are very strong fibers because of
inter-chain hydrogen bonding. There are
regions of microcrystallinity, highly or-dered
chain segments, in the material.
Copyright © Houghton Mifflin Company. All rights reserved.
3–93
13.12 Condensation Polymers
Copyright © Houghton Mifflin Company. All rights reserved.
From Wikipedia
3–94
13.12 Condensation Polymers
O
C
N
H
O
C
N
H
O
C
N
H n
Kevlar, high strength aramid
O
C
O
C
N
H
N
H n
Nomex, heat-resistant aramid
Aramids are polyamides with aromatic components. They are even stronger than
Nylon 6,6, and are used for demanding
applications, such as armor.
Copyright © Houghton Mifflin Company. All rights reserved.
3–95
13.12 Condensation Polymers
CH2
O
C
N
N
C
O
+ HO R OH
Methylene diphenylisocyanate (MDI)
O
O
C
CH2
N
H
N
H
O
C
O R O
n
Polyurethanes are polymeric carbamates. They
are resilient, elastomeric, and can be made
into foams. There are many structures, but
most involve reactions between diisocyanates and diols.
Copyright © Houghton Mifflin Company. All rights reserved.
3–96
13.12 Condensation Polymers
Proteins and peptides are naturally-occurring
polyamides formed from amino acids.
H
N
H
R
CH
C
O
OH
H
N
H
R
CH
C
O
H
N
CH
R
O
C
N
H
n
R
CH
C
O
OH
There are ~20 amino acids with different R’s.
Proteins are long polymers, n > 50
Peptides are short polymers, n < 50
Copyright © Houghton Mifflin Company. All rights reserved.
3–97
Important Polyamides
O
C
N
(CH2)4
HProteins
H
N
C
O
C
O
H
N
O
C
N
H
and
(CH2)6
O
C
N
H
peptides
n
Nylon 6,6
are
naturally-occurring
O
polyamides
formed from
(CH2)5
C
Nylon 6
N
amino acids.
H n
CH
R
O
C
N
H
n
Copyright © Houghton Mifflin Company. All rights reserved.
Polypeptides,
Proteins
3–98