CHAPTER 14 –ALCOHOLS, PHENOLS, ETHERS AND THIOLS
ALCOHOLS:
R-OH
NAMING ALCOHOLS
1. Change the final –e to –ol
2. Select the longest chain containing the –OH group and number from the end nearest to the –OH group. Specify
the carbons with the –OH by number (followed by a hyphen) immediately before the name of the alcohol and
after the names of any substituents.
Study the examples below. Then name molecules a-c and draw molecules d-f at the bottom of the page:
EXAMPLES:
2-butanol
3-methyl-2-butanol
H3C
H3C
HO
3-chloro-2-methyl-2-pentanol
CH3
H3C
OH
H3C
CH3
CH3
HO
b.
c.
c. 4-fluoro-2-methyl-3-pentanol
d. CH3CH2CH2CH(OH)CH3
a.
b. 3-octanol
F
CH3
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NAMING ALCOHOLS AS A SUBSTITUENT OF AN ALKYNE OR ALKENE:
TRADITIONAL
CHEM SKETCH (MODERN IUPAC)
H3C
CH3
HO
(4E)-hex-4-en-2-ol
When the alcohol is in a chain with a double or triple bond, the –OH group is called a “hydroxy” group. How else is the
name of this molecule different than expected. Can you figure out why?
NOTE: The modern IUPAC system has a different way of approaching this molecule. If you were to draw the molecule in
CHEMSKETCH, the name it would give you would be: (4E)-hex-4-en-2-ol. Can you figure out the system? In this case,
the alcohol keeps its IUPAC priority of higher than multiple bonds, both in numbering and in its position in naming the
molecule.
Study the molecules below. Each represents a slightly more advanced example of naming alcohols. When you are
comfortable with the naming system, try naming/drawing molecules a-f.
H3C
OH
OH
OH
OH
Cl
H3C
CH3
5-chloro-2,4-hexanediol
CH3
CH
3-methyl-cyclohexanol
3-hydroxy-1-butynol
but-3-yn-2-ol
CH3
OH
-or-
Try:
CH3
OH
H3C
OH
H3C
CH3
OH
CH3
H3C
a.
b.
c.
d. 1,2,3-propane triol
e. 4-hydroxy-1-hexynol
f. 5-ethyl-cyclohexanol
2
NAMING PHENOLS:
OH
OH
OH
Cl
OH
CH3
CH3
phenol
2-methylphenol
3-methylphenol
m-cresol
Br
4-bromo-2-chlorophenol
o-cresol
ETHERS -
NAMING ETHERS:
H3C
O
CH3
1. Identify and name each chain. Use the –yl ending.
2. Add the word “ether”
Ex (above: ethyl propyl ether). Arrange the chain names in alphabetical order.
EXAMPLES:
H3C
O
CH3
diethyl ether
TRY: Study the examples above. Then name the molecules in the chart below:
CH3
H3C
O
OH
H3C
O
CH3
H3C
H3C
CH3
3
CLASSIFYING ALCOHOLS: 1° (primary), 2° (secondary) & 3° (tertiary)
For the purpose of predicting reaction products, alcohols will often be classified by the number of carbon atoms
immediately attached to the alcohol containing carbon, as demonstrated below.
This is a primary alcohol. The –OH is
attached to a carbon that is attached
to one other carbon atom.
This is a secondary alcohol. The –OH
group is attached to a carbon that is
attached to two other carbon atoms.
This is a tertiary alcohol. The –OH
group is attached to a carbon that is
attached to three other carbon atoms.
TRY: Identify each of the alcohols below as primary, secondary or tertiary.
H3C
CH3
H3C
CH3
HO
H3C
H3C
OH
OH
CH3
H3C
H3C
CH3
CH3
CH3
CH3
CH3
OH
OH
H3C
OH
4
PRACTICE: Draw or name each of the molecules in the chart below.
F
g. 3-methyl-2-hexanol
H3C
CH3
HO
H3C
a.
CH3
h. 5-ethyl-2,4-heptanediol
H3C
OH
H3C
b.
OH
i. m-nitrophenol
H3C
Cl
HO
c.
OH
j. phenyl-methyl-ether
H3C
d.
CH3
H3C
k. (CH3)3CCH(OH)CH3 (draw and name)
OH
CH3
e.
l. (CH3)3COCH2CH3 (draw and name)
H3C
O
CH3
f.
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PROPERTIES OF ALCOHOLS AND ETHERS:
POLARITY, SOLUBILITY AND MELTING POINT
1.
Review of intermolecular forces:
a.
Van der Waals Forces:
London dispersion forces (dispersion)
Dipole-dipole attractions
b.
2.
Hydrogen bonding
Molar Mass
POLARITY OF ALCOHOLS VS. ETHERS
EXAMPLE:
ethanol
propane
BP = 78.4C
dimethyl ether
BP = -24C
BP = -42C
6
PROPERTIES & USES OF ALCOHOLS , PHENOLS & ETHERS
Melting and boiling points:
TRY: Arrange the molecules:
Solubility in water:
2-hexanol, heptane, phenol, butane, dipropyl ether and 3-butanol in order of:
1.
Increasing boiling point:
2.
Increasing solubility in water:
USES:
Ethanol
Distillation
Proof
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Gasohol
Solvent
Denatured ethanol
methanol
isopropanol
ethylene glycol
glycerol
PHENOLS:
weakly acidic (like phenolpthalien)
ETHERS
melting point:
solvent properties:
diethyl ether:
8
REACTIONS OF ALCOHOLS
NAME
dehydration
CONDITIONS
strong acid (usually H2SO4) and
heat (above 180°)
Condensation
(primary alcohol; symmetric
ether formation only)
strong acid (usually H2SO4) and
lower temp (below 180°); excess
amount of alcohol
***Condensation
Williamson Ether Synthesis
Alcohol + primary halide (works
best)
Strong base catalyst, usually Na
oxidation (primary alcohol)
Oxidizing agent (O)
K2Cr2O7
KMnO4
oxidation (secondary alcohol)
Oxidizing agent (O)
K2Cr2O7
KMnO4
oxidation (tertiary alcohol)
REACTION
No reaction
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PRACTICE REACTIONS
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REACTION WRITING PRACTICE:
1. Predict and draw the products of each reaction below:
a. 2 1-propanol  acid catalyst, 120°C
b. 1-propanol  acid catalyst, above 180°C
c. 1-propanol  oxidation (KMnO4)
d. isopropanol  oxidation (KMnO4)
e. 1-propanol + 1-bromobutane  (Na catalyst)
Name and write the reaction needed to synthesize each compound listed below. Include all necessary catalysts and
reaction conditions.
__________________________ a. propylene
__________________________ b. dimethyl ether
__________________________ c. butanal (CH3CH2CH2CHO )
__________________________ d. 2-pentanone (CH3COCH2CH2CH3)
__________________________ e. methyl pentyl ether
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Acid – Base Properties of Alcohols:
REVIEW:
Bronsted-Lowry Acid:
Example:
acid
base
conjugate base
conjugate acid
Alcohols as Acids: (in the presence of a strong base)
H3C
OH
+
Na
Bronsted-Lowry Base:
Example:
base
acid
conjugate acid
conjugate base
Alcohols as Bases: (in the presence of a strong acid)
H3C
OH
+
+
H
12
REACTION MECHANISMS FOR ALCOHOLS
Dehydration: above 180°, with strong acid catalyst
Step 1: An acid/base reaction.
Protonation of the alcoholic
oxygen to make a better leaving
group. This step is very fast and
reversible. The lone pairs on the
oxygen make it a Lewis base.
Step 2:
Cleavage of the C-O bond allows
the loss of the good leaving
group, a neutral water molecule,
to give a carbocation
intermediate. This is the rate
determining step (bond breaking
is endothermic)
Step 3:
An acid/base reaction.
Deprotonation by a base (a water
molecule) from a C atom adjacent
to the carbocation center leads to
the creation of the C=C
VOCABULARY:
TRY:
Ethanol (acid catalyst, above 180°C)
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Condensation: Below 180°, with
strong acid catalyst (ether formation)
USED FOR PRIMARY ALCOHOLS, SYMMETRICAL ETHER SYNTHESIS
Step 1:
VOCABULARY:
An acid/base reaction.
Protonation of the alcoholic
oxygen to make a better leaving
group. This step is very fast and
reversible. The lone pairs on
the oxygen make it a Lewis
base.
Step 2:
The O of the second alcohol
molecule functions as the
nucleophile and attacks to
displace the good leaving group,
a neutral water molecule, by
cleaving the C-O bond. This
creates an oxonium ion
intermediate.
Step 3:
Another acid / base reaction.
The proton is removed by a
suitable base (here a water
molecule, ROH is another
alternative) to give the ether
product.
1-pentanol  (acid catalyst, below 140°C)
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MECHANISM OF THE WILLIAMSON ETHER SYNTHESIS
The strong base strips the electron
from –OH, leaving the O with a
negative charge
TRY: 2-propanol with ethyl chloride (Na as
catalyst)
The alkoxide functions as the
nucleophile and attacks the
electrophilic C of the alkyl
halide displacing the bromide
and creating the new C-O
bond. This is an example of an
SN2 reaction.
TRY:
1-propanol + ethyl bromide  (Na as a catalyst)
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THIOLS (mercaptans)
1.
Naming: add “thiol” to the name of the molecule
Examples:
SH
SH
SH
H3C
H3C
SH
ethanethiol
CH3
butane-2-thiol
cyclohexanethiol
benzenethiol
2-butanethiol
2.
Formation of disulfide “bridges”
Oxidation:
Proteins (cysteine)
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