1. Ethers and Epoxides Chem 145 Chapter 8 1434-1435 2013-2014
2nd semester

2. Chapter’s out line Ethers Cyclic Ethers; “Epoxides”
Definition; General formula; Classification and Types
Nomenclature
- Common Names.
- IUPAC Naming.
Physical Properties
General methods of preparation of ethers
A- Dehydration of Alcohols.
B- Williamson Synthesis.
Reactions of ethers
Cyclic Ethers; “Epoxides”
Definition
General methods of preparation of Epoxides
Reaction of Epoxides.

3. Definition Classification of Ethers
Ether is a class of organic compounds that
contain an ether group — (an oxygen atom connected to
two alkyl or aryl groups) — of general formula R–O–R’.
Classification of Ethers
(I) Aliphatic Ethers
(II) Aromatic Ethers
Aliphatic ethers are those in which
R and R' are both alkyl groups.
Aromatic ethers are those in which
either one or both R and R' are aryl groups.
Example:
Examples:
Methyl phenylether
Butylmethylether
Diphenylether

4. Nomenclature: A. Common Names.
In the Common system the ethers are named according to the alkyl group bonded to the oxygen atoms.
The two-alkyl groups bonded to the functional group (- O -) are written alphabetically followed by the word ether.
Examples
CH3 - O - C2H5
Ethyl methyl ether
Ethyl phenyl ether
Diethylether
Tert-butylmethyl ether

5. B. IUPAC System For Ethers
The names for ethers are based on the alkane name of the longest chain attached to the oxygen.
The shorter alkyl group and the oxygen are named as an alkoxy group attached to the longer alkane.
methoxy
propane
They are named as alkoxyalkanes.
Numbering the longer alkane gives
CH3—O—CH2—CH2—CH3
1-methoxypropane.
alkoxy group
Alkyl Group
Name
Alkoxy Group
CH3-
Methyl
CH3O-
Methoxy
CH3CH2-
Ethyl
CH3CH2O-
Ethoxy
(CH3)2CH-
Isopropyl
(CH3)2CHO-
Isopropoxy
(CH3)3C-
tert-Butyl
(CH3)3CO-
tert-Butoxy
C6H5-
Phenyl
C6H5O-
Phenoxy

6. Examples 1-Methoxy-2-methyl propane Methoxy cylohexane Propoxy butane3 2 1
1-Methoxy-2-methyl propane
Methoxy cylohexane
(c)
(d) 1 2 3 4
Propoxy butane
1-Ethoxy-1-methyl Cyclohexane

7. 5-ethoxy-2-heptene
1-phenoxy-1-propene
Common:
Diphenylether
Methylphenylether
Anisol
IUPAC:
Phenoxy benzene
Methoxy benzene

8. 1- Give the name of the following molecules (IUPAC & Common)
Exercise:
1- Give the name of the following molecules (IUPAC & Common)
2- Draw the correct structure for the following
A) Methyl vinyl ether
B) Methoxy hexane

9. Physical Properties 1. Solubility of Ethers
Ethers containing up to 3 carbon atoms are soluble in water, due to their hydrogen bond formation with water molecules.
Ethers can form hydrogen bonds with water molecules
The solubility decreases with increase in the number of carbon atoms.
The relative increase in the hydrocarbon portion of the molecule
decreases the tendency of H-bond formation.

10. O 2. Boiling Points of Ethers
Ethers have an O atom, but there is no H attached.
Thus, hydrogen bonds cannot form between ether molecules. O R R’
Ether molecules cannot form hydrogen bonds with other ether molecules.
Butane
Methoxyethane
1-Propanol
(butane)
(ethyl methyl ether)
(Propyl alcohol)
M.W. = 58
M.W. = 60
M.W. = 60
b.p. = °C
b.p. = 7.9 °C
b.p. = 97.2°C

11. General methods of preparation of ethers
A- Dehydration of Alcohols.(only symmetric ethers)
This method is used for industrially preparation for symmetric ethers.
In the presence of acid, two molecules of an alcohol may lose water to form an ether.
General Equation
/140°C
Examples

12. B- Williamson Synthesis.
The reaction of a sodium alkoxide; RONa or a sodium phenoxide; ArONa with an alkyl halide to form an ether is known as the Williamson synthesis.
- It is an important laboratory method for the preparation of symmetrical and unsymmetrical ethers.
- The reaction involves nucleophilic substitution of an alkoxide ion for a halide ion.
General Equations
Sodium alkoxide
Alkyl ether
Alkyl halide
Sodium phenoxide
Aryl ether
Alkyl halide

13. Examples
Note that !
The alkoxide is commonly made by adding Na or K to the alcohol
Examples

14. Reactions of Ethers Cleavage of Ethers by Acides
Ethers undergo just one kind of basic chemical reaction: cleavage by acids.
Cleavage of Ethers by Acides
Ethers are cleaved by HX to an alcohol and a haloalkane.
General Equation
Ether
Conc. acid
Alkyl halide
alcohol
Specific Example
Dimethyl ether
Hydrogen bromide
Methyl bromide
Methyl alcohol

15. Note: If two or more equivalents of acid are used further dehydration can occur on formed alcohols which may react further to form a second mole of alkyl halide.
Example
Diethyl ether
Excess
Hydrogen bromide
Ethyl bromide

16. Cyclic Ethers; “Epoxides”

17. Definition Epoxides Epoxides or Cyclic ethers
An epoxide
Epoxides are cyclic ethers in which the ether oxygen is part of a three-membered.
The simplest and the most important epoxide is ethylene oxide.
Ethylene oxide

18. General methods of preparation of Epoxides
Peroxide Epoxidation
Epoxides are often prepared from reacting with organic peroxy acids
(“peracids”) ex; CH3C(O)OOH in a process called epoxidation.
General equation
Peroxy acid
Epoxide
MCPBA
Note that:
MCPBA=

19. Example
propene
propeneoxide

20. Reaction of Epoxides Ring-opening reactions of epoxides:
Epoxides are highly strained and easily undergo ring-opening reactions under both acidic and basic conditions.
For the same reason epoxides have the tendecy to open up its ring. Thus oxygen atom combines with the reactive hydrogen atom of vairous compounds to form a hydroxy group, -OH, as shown in the next slide.
General Equation
Ethylene oxide
Addition Product

21. Reaction of Epoxides. + 1,2-Ethandiol 2-Methoxyethanol
Ethylene halohydrin
2-Halo ethanol
Ethylene oxide
Alkyl alcohol

22. Thank you
For your attention