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Chemistry 2100
Chapter 14
ALCOHOLS
ETHERS
THIOLS
O
O
R
H
alcohol
R
S
R'
ether
R
H
thiol / mercaptan
(sulfhydryl)
Common Nomenclature
IUPAC Nomenclature
• alkyl "alcohol"
• dialkyl "ether"
• "e"
"ol"
• locator numbers
Alcohols
Alcohol: A compound that contains an -OH
(hydroxyl) group bonded to a tetrahedral carbon.
– Methanol, CH3OH, is the simplest alcohol.
Nomenclature
1. Select the longest carbon chain that contains the -OH group
as the parent alkane and number it from the end that gives
the -OH the lower number.
2. Change the ending of the parent alkane from -e to -ol and use
a number to show the location of the -OH group; for cyclic
alcohols, the carbon bearing the -OH group is carbon-1.
3. Name and number substituents and list them in alphabetical
order.
Nomenclature
– In the IUPAC system, a compound containing two hydroxyl
groups is named as a diol, one containing three hydroxyl
groups as a triol, and so forth.
– IUPAC names for diols, triols, and so on retain the final "-e"
in the name of the parent alkane.
– We commonly refer to compounds containing two hydroxyl
groups on adjacent carbons as glycols.
CH2 CH2
OH OH
1,2-Eth anediol
(Eth ylen e glycol)
CH3 CHCH2
HO OH
1,2-Propan ediol
(Propylene glycol)
CH2 CHCH2
OH OHOH
1,2,3-Propan etriol
(Glycerol, Glycerin)
Physical Properties
Alcohols are polar molecules.
– The C-O and O-H bonds are both polar covalent.
Physical Properties
In the liquid state,
alcohols associate
by hydrogen
bonding.
boiling points (°C)
CH3OH
65°
CH3CH2CH2OH
97°
CH3CH3
-88°
CH3CH2CH2CH3
0°
CH3Cl
-24°
CH3CH2CH2Cl
PhOH
182°
CH3CH2CH2CH2OH
118°
PhCH3
110°
(CH3)2CHCH2OH
108°
PhCl
132°
(CH3)3COH
46°
83°
solubility (g / 100 mL H2O)
CH3CH2OH
∞
CH3CH2CH2OH
∞
CH3CH2CH2CH2OH
8.3
CH3CH2CH2CH2CH2OH
2.4
CH3CH2CH2CH2CH2CH2OH
0.6
CH3CH2CH2CH2CH2CH2CH2CH2OH
0.05
CH3CH2OCH2CH3
7.8
(CH3)2CHCH2OH
10.0
(CH3)3COH
∞
C6H11OH
3.6
Acidity of Alcohols
Alcohols have about the same pKa values as water.
• Aqueous solutions of alcohols have the same pH as
that of pure water.
– Alcohols and phenols both contain an OH group.
– Phenols are weak acids and react with NaOH and other
strong bases to form water-soluble salts.
n
– Alcohols are weaker acids than phenols and do not react in
this manner.
11
Preparing Alcohols
Fermentation
C12H22O11
+
H 2O
zymase
4 C2H5OH
+
4 CO 2 O
ethanol
sucrose
Alkene Hydration
H
C C
H
H H
H
+
H
H2 O
H OH
H2SO 4
H
C C
H OH
H
Dehydration
CH3 CH2 OH
Ethan ol
OH
Cyclohexanol
H 2 SO4
180°C
H2 SO4
140°C
CH2 =CH2 + H2 O
Ethylen e
+ H2 O
Cyclohexene
CH3
CH3
H2 SO4
CH3 CCH3
CH3 C=CH2 + H2 O
50°C
OH
2-Methyl-2-propanol
2-Methylpropene
(Isobutylene)
(t ert -Butyl alcohol)
Oxidation of Alcohols
(1°)
(2°)
H+
CH3
O
H
C
H
H
O
[ O]
H
CH3
C
H
H
H
••
N
N
Ad
Ad
NAD +
NAD H
H+
CH3
O
H
C
H
H
O
[ O]
H
CH3
C
H
H
H
••
N
N
Ad
Ad
NAD +
NAD H
H+
CH3
O
H
C
H
H
O
[ O]
H
CH3
C
H
H
H
••
N
N
Ad
Ad
NAD +
NAD H
H+
CH3
O
H
C
H
H
O
[ O]
H
CH3
C
H
H
H
••
N
N
Ad
Ad
NAD +
NAD H
H+
CH3
O
H
C
H
H
O
[ O]
H
CH3
C
H
H
H
••
N
N
Ad
Ad
NAD +
NAD H
H+
CH3
O
H
C
H
H
O
[ O]
H
CH3
C
H
H
H
••
N
N
Ad
Ad
NAD +
NAD H
H+
CH3
O
H
C
H
H
O
[ O]
H
CH3
C
H
H
H
••
N
N
Ad
Ad
NAD +
NAD H
H+
CH3
O
H
C
H
H
O
[ O]
H
CH3
C
H
H
H
••
N
N
Ad
Ad
NAD +
NAD H
Ethers
Common Nomenclature
IUPAC Nomenclature
• dialkyl "ether"
• dialkyl "ether"
• "alkoxy"
Physical Properties
Ethers are polar molecules in which oxygen bears a
partial negative charge and each carbon bonded to it
bears a partial positive charge.
Physical Properties
However, only weak forces of attraction exist
between ether molecules in the pure liquid.
– Consequently, boiling points of ethers are close to
those of hydrocarbons of similar molecular weight.
– Ethers have lower boiling points than alcohols of
the same molecular formula.
Reactions of Ethers
Ethers resemble hydrocarbons in their resistance to
chemical reaction.
– They do not react with oxidizing agents such as potassium
dichromate.
– They do not react with reducing agents such as H2 in the
presence of a transition metal catalyst or with hydride
reducing agents such as NaBH4.
– They are not affected by most acids or bases at moderate
temperatures.
Because of their general inertness and good solvent
properties, ethers, such as diethyl ether and THF, are
excellent solvents in which to carry out organic
reactions.
H H
H H H H H
H
C
C C
C
C H
H H H H H
pentane
bp 36°C
H
C
H H
C O C
H H
C H
H H
(diethyl) ether
bp 36°C
7.8 g/100 mL
H H H H
H
C
C C
C O H
H H H H
1-butanol
bp 118°C
8.3 g/100 mL
Anesthetics
F Cl
F
C C Br
F
H
halothane
F
F
F
F
C O C C Cl
H
F
enflurane
H
F
F
Cl F
C O C C F
F
H
isoflurane
F
p. 409
Thiols
Thiols
Thiol: A compound containing an -SH
(sulfhydryl group).
– The most outstanding property of low-molecularweight thiols is their stench.
– They are responsible for smells such as those from
rotten eggs and sewage.
– The scent of skunks is due primarily to these two
thiols.
Naming thiols
Alkane + thiol
1-propanethiol
2-propene-1-thiol
Physical Properties
Because of the small difference in
electronegativity between sulfur and
hydrogen (2.5 - 2.1 = 0.4), an S-H bond is
nonpolar covalent.
– Thiols show little association by hydrogen bonding.
– Thiols have lower boiling points and are less
soluble in water and other polar solvents than
alcohols of similar molecular weight.
CH3CH2OH (bp 78°C)
CH3OCH3 (bp -24°C)
CH3CH2SH (bp 35°C)
CH3SCH3 (bp 37°C)
Oxidation
R
••
S
R'
••
sulfide (thioether)
[ O]
O
R
S
••
R'
sulfoxide
[ O]
O
R
S
O
sulfone
R'
O
H S CH 2
CH
NH 2
cysteine
C
OH
S
S
S
S
[ H]
SH
SH
SH
SH
[ O]
S S
S S
S
S
S
S
[ H]
SH
SH
SH
SH
[ O]
S S
S S
S
S
S
S
[ H]
SH
SH
SH
SH
[ O]
S S
S S
-helix
-helix
-helix
-helix
-helix
-helix
-helix
-helix
-helix
-pleated sheet
-pleated sheet
-helix
-pleated sheet
-helix
-pleated sheet
salt bridge
O
-O
C
NH3+
-helix
-pleated sheet
-helix
-pleated sheet
salt bridge
O
-O
C
NH3+
CH2
O
H
-helix
hydrogen
bond
O
H
CH2
-pleated sheet
-helix
-pleated sheet
hydrogen
bond
H N
OH
H
C O
salt bridge
O
-O
C
NH3+
CH2
O
H
-helix
hydrogen
bond
O
H
CH2
-pleated sheet
-helix
hydrophilic
interaction
to water
-pleated sheet
HO
CH2
NH2
HO
O
C
hydrogen
bond
CH2
H N
OH
CH 2
H
C O
salt bridge
O
-O
C
NH3+
CH2
O
H
-helix
hydrogen
bond
O
H
CH2
-pleated sheet
-helix
hydrophilic
interaction
to water
-pleated sheet
-helix
HO
CH2
CH2
NH2
HO
O
C
hydrogen
bond
CH2
H N
OH
CH 2
H
hydrophobic
interaction
C O
salt bridge
CH2
O
-O
C
NH3+
CH2
O
H
-helix
hydrogen
bond
O
H
CH2
-pleated sheet
hydrophilic
interaction
to water
-pleated sheet
-helix
HO
CH2
CH2
NH2
HO
O
C
hydrogen
bond
CH2
H N
OH
CH 2
H
hydrophobic
interaction
C O
salt bridge
CH2
O
-O
C
NH3+
CH2
O
H
-helix
hydrogen
bond
O
H
CH
CH3 CH3
CH2
-pleated sheet
CH3
hydrophilic
interaction
to water
-pleated sheet
-helix
HO
CH2
CH2
NH2
HO
O
C
hydrogen
bond
CH2
H N
OH
CH 2
CH
CH3 CH3
hydrophobic
interaction
H
C O
salt bridge
O
-O
NH3
S
C
S
+
CH2
CH2
disulfide
bond
S
S
O
H
-helix
hydrogen
bond
O
H
CH2
-pleated sheet
CH3