Download Chapter 22 HEIN

Alcohols, Ethers,
Phenols, and Thiols
Chapter 22
Hein * Best * Pattison * Arena
Version 1.0
Colleen Kelley
Chemistry Department
1 College
Pima Community
© John Wiley and Sons, Inc.
Chapter Outline
22.1 Functional Groups
22.2 Classification of
Alcohols
22.4 Physical Properties of Alcohols
22.5 Chemical Properties of
Alcohols
22.3 Naming Alcohols
2
Chapter Outline (continued)
22.6 Common Alcohols
22.7 Phenols
22.8 Properties of Phenols
22. 9 Production of Phenol
22.10 Ethers
22.11 Structures and
Properties of Ethers
22.12 Preparation of Ethers
22.13 Thiols
3
Functional Groups
4
• The various classes of compounds
are identified by the presence of
certain characteristic groups called
functional groups.
• Through the chemical reactions of
functional groups, it is possible to
create or synthesize new
substances.
5
O
O
H
O
H
water
R
H
alcohol
H
O
R
R
ether
phenol
6
Classification of
Alcohols
7
• Alcohols are classified as primary (1°), secondary
(2°), or tertiary (3°) depending on whether the
carbon atom to which the –OH group is attached is
directly bonded to one, two, or three other carbon
atoms respectively.
H
C
C
C
C
OH
C
C
OH
H
primary (1o)
secondary (2 )
alcohol
alcohol
C
C
OH
C
H
o
tertiary (3o)
alcohol
8
9
10
•Polyhydroxy alcohols and polyols are
general terms for alcohols that have
more than one –OH group per molecule.
•Polyhydroxy compounds are very
important molecules in living cells, as
they include the carbohydrate class of
biochemicals.
11
Structural Representations of Alcohols
• An alcohol such as 2-butanol can be written
in a single-line formula by enclosing the –
OH group in parentheses and placing it after
the carbon to which it is bonded.
OH
CH3CH2CHCH3 = CH3CH2CH(OH)CH3
12
Application to Biochemistry
Blood sugar (glucose) contains five
alcohol groups. Using the structure of
glucose shown here, label each group
as 1°, 2°, or 3°.
O=CHCH(OH)CH(OH)CH(OH)CH(OH)CH2OH
13
Application to Biochemistry
secondary
H
C
O
OH
H
OH
OH
C
C
C
C
H
OH
H
CH 2OH
primary
H
secondary
14
Naming Alcohols
15
IUPAC Rules for Naming Alcohols
1. Select the longest continuous chain of
carbon atoms containing the –OH group.
2. Number the carbon atoms in this chain
so that the one bearing the -OH group
has the lowest possible number.
16
IUPAC Rules for Naming Alcohols
3. Form the parent alcohol name by replacing
the final –e of the corresponding alkane by
–ol. When isomers are possible, locate the
position of the –OH group by placing the
number (hyphenated) of the carbon atom to
which the –OH is bonded immediately
before the parent alcohol name.
4. Name each alkyl side chain (or other group),
and designate its position by number.
17
Name CH3CH2CH2CH2OH
4 3 2 1
CH3CH2CHCH2OH
1-butanol
18
Nomenclature of Alcohols
OH
CH3
H3C CH
CH3
2-propanol
(isopropyl alcohol)
OH
cyclohexanol
H3C
CH
CH2CH2OH
3-methyl-1-butanol
HO
OH
1,3-cyclohexanediol
19
Physical Properties
of Alcohols
20
Physical Properties of Alcohols
• The physical properties of alcohols are
related to those of both water and
alkane hydrocarbons.
• An alcohol molecule is made up of a
waterlike hydroxyl group joined to a
hydrocarbonlike alkyl group.
O
H
O
H
water
R
H
alcohol
21
Boiling Points of Alcohols
• Alcohols have relatively high boiling
points.
• The boiling points of the normal alcohols
increase in a regular fashion with increasing
number of carbon atoms.
• Branched-chain alcohols have lower boiling
points than corresponding straight-chain
alcohols.
22
23
• Alcohols containing up to three carbon
atoms are infinitely soluble in water.
• The –OH group on the alcohol
molecule is responsible for both the
water solubility and relatively high
boiling points of the low-molar-mass
alcohols.
24
Hydrogen Bonding in Alcohols
H
O
H
H
R
O
R
O
H
O
H
H
R
H
O
O
O
H
O
R
H
R
H
H
water-alcohol
alcohol-alcohol
25
26
27
Glucose is one of the most important
carbohydrates in biochemistry. It has six
carbons and five alcohol groups (molar
mass = 180.2 g). How would you predict
the water solubility of glucose to differ
from that of 1-hexanol?
28
H
OH
H
OH
OH
C
C
C
C
C
O
H
OH
H
H
CH 2OH
95 g of glucose will dissolve in 100 g of water.
OH
0.6 g of 1-hexanol will dissolve in 100 g of water.29
Chemical Properties
of Alcohols
30
Chemical Properties of Alcohols
•
•
•
•
Acidic and Basic Properties
Oxidation
Dehydration
Esterification
31
Basic Properties
•
If an alcohol is mixed with a strong
acid, it will accept a proton (act as a
Brønsted-Lowry base) to form a
protonated alcohol or oxonium ion.
H
H3C
O
H + H2SO4
H3C
-
+ HSO4
O
H
32
Acidic Properties
•
•
2 H3C
Alcohols can also act as BrønstedLowry acids.
The resulting anion in the alcohol
reaction is known as an alkoxide ion
(RO-).
H2
C
O
H + 2 Na
2 H3C
H2
C
Na+
O
+ H2 (g)
sodium ethoxide
33
Reactivity of Alcohols with Na or K
•
The order of reactivity of alcohols
with sodium or potassium is:
– primary > secondary > tertiary.
•
Reactivity decreases with increasing
molar mass, since the –OH group
becomes a relatively smaller, less
significant part of the molecule.
34
Oxidation
• Oxidation is the loss of hydrogen or the
gain of bonds to oxygen by the organic
reactant.
• Carbon atoms exist in progressively higher
stages of oxidation in different functional
groups.
Alkanes
Alcohols
Aldehydes
Ketones
Carboxylic
Acids
Carbon
dioxide
increasing oxidation state
35
36
H
R
C
O
O
OH
[O]
R
C
H + H2O
aldehyde
H
primary (1o)
[O]
R
C
OH
carboxylic
acid
alcohol
R
R
C
O
OH
[O]
R
C
R
ketone
H
secondary (2o)
alcohol
The –OH group gives
an organic compound
the capability of
forming an aldehyde,
ketone, or carboxylic
acid.
R
R
C
OH
[O]
No reaction
R
tertiary (3o)
alcohol
37
Common Oxidizing Agents
• KMnO4
• K2Cr2O7
• O2
38
Dehydration
• Alcohols can be dehydrated with
sulfuric acid to form alkenes.
H
H
H
C
C
H
OH
96% H2SO4
H
H heat
H
H
C
C
H + H2O
39
Dehydration
• For many alcohols, there is more than one way to
remove water. Therefore the double bond can be located
in different positions.
• The major product in such cases is the alkene in which
the C=C bond has the greatest number of alkyl
substituents on it (or the least number of hydrogens).
H
H3C
H
H
C
C
96% H2SO4
CH2
H3C
heat
H
OH
H
2-butanol
C
H
C
CH3 + H3C
2-butene
(major product)
H2
C
H
C
CH2 + H2O
1-butene
40
Saytzeff’s Rule
During intramolecular dehydration, if
there is a choice of positions for the
carbon-carbon double bond, the
preferred location is the one that
generally gives the more highly
substituted alkene – that is, the alkene
with the most alkyl groups attached to
the double-bond carbons.
41
Dehydration
• Primary alcohols can be dehydrated
with sulfuric acid to form ethers.
H3C
H3C
H2
C
H2
C
OH
OH
96% H2SO4
H3C
heat
H2
C
O
H2C
CH3 + H2O
diethyl ether
• A reaction in which two molecules are combined by
removing a small molecule is known as a
condensation reaction.
42
Esterification
(Conversion of Alcohols to Ethers)
• An alcohol can react with a carboxylic
acid to form an ester and water.
O
O
+
H
R
C
OH
carboxylic
acid
+ H-OR'
alcohol
R
C
OR' + H2O
ester
43
Utility of the Hydroxyl
Functional Group
44
Common Alcohols
45
Three General Methods for
Making Alcohols
1. Hydrolysis of an ester.
2. Alkaline hydrolysis of an alkyl halide
(1° and 2° alcohols only).
3. Catalytic reduction of aldehydes and
ketones.
46
Hydrolysis of an Ester
• Hydrolysis is a reaction of water with
another species in which the water
molecule is split.
O
O
+
H
H2O + R'O
C
ester
R
heat
H-OR' + HO
C
R
alcohol
carboxylic
acid
47
Alkaline hydrolysis of an alkyl
halide (1° and 2° alcohols only).
CH3CH2Cl + NaOH(aq)  CH2CH3OH + NaCl
48
Catalytic Reduction of
Aldehydes and Ketones
• Produces primary and secondary
alcohols.
• Chapter 23
49
Methanol
•Methanol is synthesized by the high-pressure
catalytic hydrogenation of carbon monoxide.
•The most economical nonpetroleum source of
carbon monoxide for making methanol is coal.
CO + 2 H2
ZnO-Cr2O3
300-400 C, 200 atm
CH3OH
50
Uses of Methanol
1. Conversion to formaldehyde (use in
manufacture of polymers).
2. Manufacture of other chemicals,
especially various kinds of esters
3. Denaturing ethyl alcohol
4. Industrial solvent
51
Ethanol
• Large quantities of ethanol are
prepared by fermentation.
– The conversion of simple sugars to
ethanol is accomplished by yeast.
• Industrially, ethanol is made by acidcatalyzed addition of water to ethylene.
C6H12O6
yeast
H2O
2 CH3CH2OH + 2 CO2
52
Uses of Ethanol
• An intermediate in the manufacture of other
chemicals such as acetaldehyde, acetic acid,
ethyl acetate, and diethyl ether.
• A solvent for many organic substances.
• A compounding ingredient for
pharmaceuticals, perfumes, flavorings, etc.
• An essential ingredient in alcoholic
beverages.
53
2-Propanol (Isopropyl Alcohol)
• 2-Propanol is made from propene.
+
CH3CH=CH2 + H2O
H
CH3CH(OH)CH3
2-propanol
54
Uses of
2-Propanol (Isopropyl Alcohol)
1. To manufacture other chemicals
(especially acetone).
2. As an industrial solvent.
3. As the principal ingredient in rubbing
alcohol formulations.
55
Ethylene Glycol (1,2-Ethanediol)
• Industrial synthesis
Ag catalyst
2 CH2=CH2 + O2
2
200-300 C
O
+ H2O
O
H+
ethylene oxide
(oxirane)
HOCH2CH2OH
1,2-ethanediol
(ethylene glycol)
56
Uses of
Ethylene Glycol (1,2-Ethanediol)
1. In the preparation of the synthetic
polyester fiber Dacron and film Mylar
2. As a major ingredient in “permanenttype” antifreeze cooling systems
3. As a solvent in the paint and plastic
industries
4. In the formulations of printing ink and ink
for ballpoint pens.
57
Glycerol (1,2,3-Propanetriol)
• Glycerol (also known as glycerine) is
an important trihydroxyalcohol.
• It is obtained as a by-product of the
processing of animal and vegetable fats
to make soap and other products.
• It is synthesized commercially from
propene.
58
Uses of Glycerol
• Each directly related to the three –OH groups.
1. As a raw material in the manufacture of
polymers and explosives.
2. As an emollient in cosmetics.
3. As a humectant in tobacco products.
4. As a sweetener.
59
Phenols
60
Phenols
• The term phenol is used for the class of
compounds that have a hydroxy group
attached to an aromatic ring.
• The parent compound is also called phenol,
C6H5OH.
OH
61
Naming Phenols
• Many phenols are named as derivatives of
the parent compound, via the general
methods for naming aromatic compounds.
OH
OH
OH
Br
phenol
m-bromophenol
NH2
p-aminophenol
62
Common Phenols
OH
OH
OH
HO
HO
resorcinol
catechol
(m-dihydroxybenzene)
(o-dihydroxybenzene)
OH
hyrdroquinone
(p-dihydroxybenzene)
63
Properties of Phenols
64
Properties of Phenols
• Colorless, crystalline solid, mp = 41 °C
• Highly poisonous
• More acidic than alcohols and water
-
O Na+
OH
+ NaOH
phenol
ROH + NaOH
alcohol
+ H2O
sodium phenoxide
no reaction
65
Production of Phenol
66
Production of Phenol
• Phenol is obtained from coal tar.
• Several commercial methods are used
to produce phenol synthetically.
67
Ethers
68
Ethers
Ethers have the general formula
ROR’
69
70
71
Naming Ethers
• Individual ethers may be known by
several names.
H3C
O
CH3
H3C
ether
methyl
O
CH2CH3
ether
methyl
dimethyl ether
methyl
ethyl
ethyl methyl ether
72
IUPAC Nomenclature of Ethers
1. Select the longest carbon continuous
chain and label it with the name of
the corresponding alkane.
2. Change the –yl ending of the other
hydrocarbon group to –oxy to obtain
the alkoxy group name.
e.g. CH3O- is called methoxy.
73
IUPAC Nomenclature of Ethers
3. Combine the two names from Steps 1 and 2,
giving the alkoxy name and its position on
the longest carbon chain first, to form the
ether name.
H3C
O
CH3O- is the
alkoxy group
(methoxy)
CH2CH3
This is the longest C-C
chain, so call it ethane.
methoxyethane
74
IUPAC Nomenclature of Ethers
H3CH2CH2C
O
CH2CH2CH2CH3
1-propoxybutane
CH3
CH3
H3CHC
O
CH3
CHCH2CHCH3
2-isopropoxy-4-methylpentane
75
Structures and Properties
of Ethers
76
Properties of Ethers
• Ethers are somewhat more polar than alkanes,
but are much less polar than alcohols.
• Ethers – especially diethyl ether – are
exceptionally good solvents for organic
compounds. H
SO H
3
O
O
H
H
hydrogen
bond
O
H3C
CH2CH3
ether-water
O
H3C
CH2CH3
ether-acid
77
78
Formation of Peroxides from Ethers
• Oxygen of the air slowly reacts with ethers
to form unstable peroxides that are subject
to explosive decomposition.
O
H3CH2C
CH2CH3
+ O2
O
H3CH2C
CHCH3
O-O-H
diethyl ether hydroperoxide
79
Preparation of Ethers
80
Williamson Synthesis of Ethers
• The alkyl halide, RX, may be a methyl
or primary group, but not a secondary or
tertiary alkyl group or an aryl group.
• The alkoxide, R’ONa, may be methyl,
primary, secondary, tertiary, or an aryl
group.
RX + R’ONa
alkyl
halide
alkoxide
 ROR’ + NaX
ether
81
Thiols
82
Thiols
• Organic compounds that contain the -SH
group are known as thiols or mercaptans.
S
H3C
H
methanethiol
(methyl mercaptan)
SH
H3C CH2CH3
2-propanethiol
83
Properties of Thiols
1. Foul odors.
2. Oxidation to disulfides:
[O]
2 RSH  R-S-S-R
thiol
disulfide
84
85