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Chapter 13:
Alcohols, Phenols, and Ethers
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ALCOHOLS, PHENOLS, AND ETHERS
• Hydroxy group – the –OH functional group
• An alcohol has an –OH group attached to an aliphatic
carbon. General formula: R-OH
• A phenol has an –OH group on a benzene ring.
• An ether has the functional group:
General formula: R-O-R’
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NAMING ALCOHOLS
Step 1: Name the longest chain to which the –OH group is
attached. Use the hydrocarbon name of the chain, drop the
final –e, and replace it with –ol.
Step 2: Number the longest chain to give the lowest number
to the carbon with the attached –OH.
Step 3: Locate the –OH position.
Example:
OH
|
CH3—CH2—CH2—CH—CH2—CH3
6
5
4
3
2
1
3-hexanol
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Step 4: Locate and name any other groups attached to the
longest chain.
Step 5: Combine the name and location of other groups,
the location of the –OH, and the longest chain into the final
name.
Example:
CH3 OH CH3
|
|
|
CH3—CH2—CH—CH—CH—CH3
6
5
4
3
2
1
2,4-dimethyl-3-hexanol
Note: Alcohols containing two –OH groups are diols, three
–OH groups are triols. The IUPAC names for these
compounds have endings of –diol and –triol rather than –ol.
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NAMING PHENOLS
• Substituted phenols are usually named as derivatives of
the parent compound phenol.
Examples:
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CLASSIFICATION OF ALCOHOLS
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PHYSICAL PROPERTIES OF ALCOHOLS
• The –OH group is polar and capable of hydrogen bonding.
• This makes low molecular weight alcohols highly soluble in
water.
• Hydrogen bonding in a water-methanol solution:
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PHYSICAL PROPERTIES OF ALCOHOLS, cont.
• Larger alkanes have greater hydrophobic regions and are
less soluble or insoluble in water.
• Water interacts only with the –OH group of
1-heptanol:
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PHYSICAL PROPERTIES OF ALCOHOLS, cont.
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PHYSICAL PROPERTIES OF ALCOHOLS, cont.
• The –OH group can hydrogen bond between alcohol
molecules leading to relatively high boiling points.
• Hydrogen bonding in pure ethanol:
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PHYSICAL PROPERTIES OF ALCOHOLS, cont.
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ALCOHOL REACTIONS
The removal of water (dehydration) from an alcohol at
180°C is an elimination reaction that produces an alkene.
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ALCOHOL REACTIONS, cont.
• Under slightly different conditions (140°C), a dehydration
reaction can occur between two alcohol molecules to
produce an ether.
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ALCOHOL REACTIONS, cont.
• Oxidation – the removal of hydrogen atoms.
• Alcohol oxidations with an oxidizing (O) agent, such as
K2Cr2O7 and KMnO4:
• Primary alcohols  aldehyde  carboxylic acid
• Secondary alcohols  ketone
• Tertiary alcohols  no reaction
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ALCOHOL REACTIONS, cont.
• Primary alcohol oxidation
• Secondary alcohol oxidation
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IMPORTANT ALCOHOLS
• Methanol (wood alcohol): CH3OH
• Production:
•Useful as a solvent and industrial starting material
• Highly toxic, if taken internally causes blindness and/or
death
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IMPORTANT ALCOHOLS, cont.
• Ethanol (ethyl alcohol, grain alcohol): CH3CH2OH
• Produced commercially from ethylene and through
biological (yeast) fermentation of carbohydrates
• Useful as a solvent, industrial starting material, fuel
(gasohol), and found in alcoholic beverages.
• Moderately toxic
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IMPORTANT ALCOHOLS, cont.
• 2-propanol (isopropyl alcohol) is the main component of
rubbing alcohol
• 1,2,3-propanetriol (glycerol) is used as a food moistening
agent (nontoxic) and for its soothing qualities (soaps)
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IMPORTANT ALCOHOLS, cont.
• Antifreezes
1,2-ethanediol (ethylene glycol)
1,2-propanediol (propylene glycol)
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PHENOLS
• Phenol behaves as a weak acid in water
and can react with bases to form salt.
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USES OF PHENOLS:
• In a dilute solution, phenol is used as a disinfectant.
• Phenol derivatives used as disinfectants:
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USES OF PHENOLS:
• Phenol derivatives used as antioxidants in food:
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PROPERTIES OF ETHERS
• Much less polar than alcohols
• More soluble in water than alkanes,
but less soluble than alcohols
• Low boiling and melting points because of the inability to
hydrogen bond between molecules
• inert and do not react with most reagents (like alkanes)
• highly flammable (like alkanes)
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• Hydrogen bonding of dimethyl ether: (a) with water and (b)
no hydrogen bonding in the pure state:
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THIOLS: THE –SH (SULFHYDRYL) GROUP
• Most distinguishing characteristic is their strong and
offensive odor
• ethanethiol – added to natural gas
• 1-propanethiol – odor in garlic and onions
• trans-2-butene-1-thiol – odor associated with skunks
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THIOL REACTIONS
• Oxidation forms disulfide (-S-S-) linkages, which are
important structural features of some proteins:
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THIOL REACTIONS, cont.
• Oxidation reactions can be reversed with a reducing agent
(H):
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POLYFUNCTIONAL COMPOUNDS
• Compounds with two or more functional groups
• Functional groups determine chemical properties of
compounds.
Example:
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