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Chapter 11
Alcohols and Ethers
Nomenclature
Nomenclature of Alcohols (Sec. 4.3F)
Nomenclature of Ethers
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 Nomenclature
 Nomenclature of Ethers
Common Names
The groups attached to the oxygen are listed in
alphabetical order
IUPAC
Ethers are named as having an alkoxyl substituent on the
main chain
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Ethers are described as symmetrical or unsymmetrical depending on whether the two groups bonded to oxygen are the same or different. Unsymmetrical ethers are also called mixed ethers. Diethyl eth
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 Cyclic ethers can be named using the prefix oxa Three-membered ring ethers can be called oxiranes;
Four-membered ring ethers can be called oxetanes
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 Physical Properties of Alcohols and Ethers
 Ether boiling points are roughly comparable to hydrocarbons
of the same molecular weight
 Molecules of ethers cannot hydrogen bond to each other
 Alcohols have considerably higher boiling points
 Molecules of alcohols hydrogen bond to each other
Both alcohols and ethers can hydrogen bond to water and have
similar solubilities in water
 Diethyl ether and 1-butanol have solubilites of about 8 g per
100 mL in water
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 Synthesis of Alcohols from Alkenes
 Acid-Catalyzed Hydration of Alkenes
This is a reversible reaction with Markovnikov regioselectivity
HA = acid ex H2SO4 ( H+ HSO4-)
 Oxymercuration-demercuration
 This is a Markovnikov addition which occurs without rearrangement
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 Organic Synthesis: Functional Group
Transformations Using SN2 Reactions
Stereochemistry can be controlled in SN2 reactions
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 Hydroboration-Oxidation
This addition reaction occurs with anti-Markovnikov
regiochemistry and syn stereochemistry
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Alcohols as Acids
 Alcohols have acidities similar to water
 Sterically hindered alcohols such as tert-butyl alcohol are less acidic
(have higher pKa values)
 Why?
1. The conjugate base is not well solvated and so is not stable
2. the alkyl group is electron donated group, so the electrons density is
increased on the -C-O-
Alcohols are stronger acids than terminal alkynes and primary or
secondary amines
An alkoxide can be prepared by the reaction of an alcohol with
sodium or potassium metal
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Conversion of Alcohols into Alkyl Halides


Hydroxyl groups are poor leaving groups, and as such, are often
converted to alkyl halides when a good leaving group is needed
Three general methods exist for conversion of alcohols to alkyl halides,
depending on the classification of the alcohol and the halogen desired
Reaction can occur with phosphorus tribromide, thionyl chloride
or hydrogen halides
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Alkyl Halides from
the Reaction of Alcohols + Hydrogen Halides
The order of reactivity is as follows
 Hydrogen halide HI > HBr > HCl > HF
 Type of alcohol 3o > 2o > 1o < methyl
Mechanism of the Reaction of Alcohols with HX
SN1 mechanism for 3o, 2o, allylic and benzylic alcohols
 These reactions are prone to carbocation rearrangements
 In step 1 the hydroxyl is converted to a good leaving group
 In step 2 the leaving group departs as a water molecule, leaving
behind a carbocation
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
In step 3 the halide, a good nucleophile, reacts with the carbocation
 Primary and methyl alcohols undergo substitution by an SN2
mechanism
 Primary and secondary chlorides can only be made with the
assistance of a Lewis acid such as zinc chloride
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 Alkyl Halides from the Reaction of Alcohols with
PBr3 and SOCl2
These reagents only react with 1o and 2o alcohols in SN2 reactions


In each case the reagent converts the hydroxyl to an excellent leaving group
No rearrangements are seen
Reaction of phosphorous tribromide to give alkyl bromides
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Synthesis of Ethers
 Ethers (symetrical) by Intermolecular Dehydration of Alcohol
 Primary alcohols can dehydrate to ethers
 This reaction occurs at lower temperature than the competing
dehydration to an alkene
 This method generally does not work with secondary or tertiary
alcohols because elimination competes strongly

The mechanism is an SN2 reaction
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Williamson Ether Synthesis
This is a good route for synthesis of unsymmetrical ethers
 The alkyl halide (or alkyl sulfonate) should be primary to avoid E2
reaction
 Substitution is favored over elimination at lower temperatures
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Reactions of Ethers

Acyclic ethers are generally unreactive, except for cleavage by very strong
acids to form the corresponding alkyl halides
 Dialkyl ethers undergo SN2 reaction to form 2 equivalents of the alkyl
bromide
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Epoxides
Epoxides are three-membered ring cyclic ethers

These groups are also called oxiranes
Epoxides are usually formed by reaction of alkenes with peroxy
acids

This process is called epoxidation and involves syn addition of oxygen
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 Reaction of Epoxides
Epoxides are considerably more reactive than regular ethers

The three-membered ring is highly strained and therefore very reactive
Acid-catalyzed opening of an epoxide occurs by initial protonation
of the epoxide oxygen, making the epoxide even more reactive

Acid-catalyzed hydrolysis of an epoxide leads to a 1,2-diol
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In unsymmetrical epoxides, the nucleophile attacks primarily at
the most substituted carbon of the epoxide
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Base-catalyzed reaction with strong nucleophiles (e.g. an alkoxide
or hydroxide) occurs by an SN2 mechanism

The nucleophile attacks at the least sterically hindered carbon of the epoxide
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