King Saud University
Chemistry Department
145 Chem 1

King Saud University
Chemistry Department
Structure and nomenclature of ethers
Ethers are compounds of formula R -O-R ', where R and R' may be alkyl groups or aryl groups.
H O H water
R O H alcohol
R O R ether
Common names (Alkyl Alkyl Ether Names)
Common names of ethers are formed by naming the two alkyl groups on oxygen and adding the word ether . Under the current system, the alkyl groups should be named in alphabetical order .
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King Saud University
Chemistry Department
Examples
Common
IUPAC
H
3
C-O-CH
3
Dimethyl ether
H
3
C-CH
2
-O-CH
2
-CH
3
Diethyl ether
Methoxy methane Ethoxy ethane
H
2
C=CH-O-CH=CH
2
Divinyl ether
H
3
C-O-C
6
H
13
H
3
C-O-CH
2
-CH
3
Common Hexyl methyl ether Ethyl methyl ether
IUPAC Methoxy hexane mehoxy ethane
H
3
C-O-CH=CH
2
Methyl vinyl ether
Methoxy ethene
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Chemistry Department
Examples
Common: Diphenyl ether
IUPAC : Phenoxy benzene
Common: Methyl Phenyl ether
(anisole)
IUPAC : Methoxy benzene
H
3
C
O
CH
3
O
CH
3
CH
3
O
H
3
C
CH
3
H
3
C
3-Methoxyhexane 5-Ethoxy-2-heptene 1-Phenoxy-1-propene
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Chemistry Department
Physical Properties of Ether
Boiling Points
The boiling points of ethers are lower than those of alcohols having the same molecular weights.
compound ethanol
Dimethyl ether propane
Formula
CH
3
-CH
2
-OH
CH
3
-O-CH
3
CH
3
-CH
2
-CH
3
MW
46
46
44
Bp (°C)
78
-25
-42
Solubility in water
 Ethers are much less soluble in water than alcohols.

More water-soluble than hydrocarbons of similar molecular weight.
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Chemistry Department
Preparation of ehers
Ethers by dehydration of alcohols
The dehydration of alcohols takes place in the presence of acid catalysts
(H
2
SO
4
, H
3
PO
4
) under controlled temperature. The general reaction for ether formation is:
Examples
R O H +
2 HO CH
3 methyl alcohol
H
+
H O R heat
H
2
SO
4
, 140 C
R O R
H
3
C O CH
3 methyl ether
(100%)
+ H
2
O
+ H
2
O
145 Chem
2 HO CH
2
CH
3 ethyl alcohol
H
2
SO
4
, 140 C
H
3
CH
2
C O CH
2
CH
3 ethyl ether
+ H
2
O
(88%)
6

King Saud University
Chemistry Department
The Williamson synthesis of ethers
R O
-
Na
+ sodium alkoxide
+ R X alkyl halide
R O R
ether
+ NaX
O
-
Na
+ sodium phenoxide
+ R X alkyl halide
R O R
ether
+ NaX
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Chemistry Department
The alkoxide is commonly made by adding Na or K to the alcohol
Examples
OH
Na
O Na
+
CH
3
CH
2
Br
OCH
2
CH
3
+ NaBr cyclohexanol
sodium cyclohexyloxide
OH
1) Na
2) CH
3
-I ethoxycyclohexane
OCH
3
2-Methoxy-3,3-dimethy p entane
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King Saud University
Chemistry Department
Reaction of Ether
Cleavage of ethers by hot concentrated acids
When ethers are heated in concentrated acid solutions, the ether linkage is broken
General equation:
R O R + H X
(concentrated) heat
Specific example
R OH + R X
CH
3
CH
2
O CH
2
CH
3
+ H I heat
CH
3
CH
2
OH + CH
3
CH
2
I
(concentrated)
The acids most often used in this reaction are HI, HBr, and HCl.
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King Saud University
Chemistry Department

If an excess of acid is present, the alcohol initially produced is converted into an alkyl halide by the reaction.
R O R + 2 H X 2 R X + H
2
O
For example
CH
3
CH
2
O CH
2
CH
3
+ 2HBr
(conc, excess) heat
145 Chem
2 CH
3
CH
2
Br + H
2
O
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King Saud University
Chemistry Department
Cyclic Ethers
Epoxide
Epoxides are cyclic ethers in which the ether oxygen is part of a three-membered ring.
C C
O an epoxide

The simplest and most important epoxide is ethylene oxide .
O ethylene oxide
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Chemistry Department
Peroxyacid Epoxidation
Peroxyacids (sometimes called peracids) are used to convert alkenes to epoxides . If the reaction takes place in aqueous acid, the epoxide opens to a glycol . Because of its desirable solubility properties, meta-chloroperoxybenzoic acid (MCPBA) is often used for these epoxidations.
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Chemistry Department
+
O
R-C-O-O-H
Example cyclohexene
Cl
MCPBA
CH
2
Cl
2
MCPBA :
O epoxycyclohexane
O
C-O-O-H
O
+
O
R-C-O-H
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Chemistry Department

Their reactivity is due to the strain in the three-membered ring , which is relieved when the epoxide ring is opened after a reaction has taken place.
 Examples of ring-opening reactions of ethylene oxide that form commercially important products are:
1- Epoxides open in acidic solutions to form glycols .
OH
O
H
3
O
+
R CH CH R R CH CH R
OH
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King Saud University
Chemistry Department
2- Epoxides open in acidic alcohol solutions to form 2-alkoxy alcohols .
O CH
3
H
3
C
..
OH +
R
O
CH CH R
H
3
O
+
R CH CH R
OH
3- When an epoxide reacts with a hydrohalic acid ( HCl,HBr, or HI), a halide ion attacks the protonated epoxide.
O
H X +
R CH CH R
X
R CH CH R
OH
4- Reactions of Epoxides with Grignard and Organolithium Reagents
OH
O
1) ether
R' MgX + R CH CH R R CH CH R
2) H
3
O +
145 Chem or R' Li
R'
15

King Saud University
Chemistry Department
Exercise 1
Give a correct name for each of the following compounds.
H
3
C O CH
2
CH
2
CH
3
CH
2
O CH
2
CH
3
CH
3
CHCH
2
CH
3
O CH
3
CH
2
=CHCH
2
O CH
2
CH=CH
2
CH
3
CH
2
CHCH=CH
2
O CH
2
CH
3
Exercise 2
O
CH
3
O CH
3
Propose a Williamson synthesis of 3-butoxy-1,1dimethylcyclohexane from 3,3-dimethylcyclohexanol and butanol.
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King Saud University
Chemistry Department
Exercise 3
Predict the products of the following reactions.
145 Chem 17