1. Ethers and Epoxides
Dr Nahed Elsayed

2. Learning Objectives Know the structure of ethers
Chapter seven discusses the following topics and by the end of this chapter the students will:
Know the structure of ethers
Know the different methods of naming ethers
Know the physical properties of ethers
Know the different methods used in preparation of ethers
Know the reactions of opened ethers with HX
Know the different methods used in synthesis of epoxides
Know the reactions of epoxides with different nucleophiles such as H2O, ROH, HX, Grignard and organolithium reagents

3. Nomenclature Of Ethers
Structure Of Ethers
Ethers: is a class of organic compounds that contain an ether linkage — an oxygen atom connected to two alkyl or aryl groups via σ bonds. thus Ethers feature C-O-C linkage — of general formula R–O–R or Ar–O–Ar or
Ar–O–R
Nomenclature Of Ethers
Common names
The common names of ethers are derived by naming the alkyl groups bonded to the oxygen then listing them in alphabetical order followed by the word "ether".
IUPAC names
The ether functional group does not have a characteristic IUPAC nomenclature suffix, so it is necessary to designate the smaller alkyl group as an alkoxy substituent of a parent compound (alkane , or alkene, or alkyne,or alcohol,----)

4. The common alkoxy substituents are given names derived from their
alkyl component
Alkyl group
Name
Alkoxy
Group Name
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

5. IUPAC Methoxy methane Ethoxy ethane Phenoxy benzene
Common Dimethyl ether Diethyl ether Divinyl ether Diphenyl ether
IUPAC Methoxy methane Ethoxy ethane Phenoxy benzene
Common Hexyl methyl ether Ethyl methyl ether Ethyl vinyl ether Methyl Phenyl ether (anisole)
IUPAC Methoxy hexane Methoxy ethane Ethoxy ethene Methoxy benzene
IUPAC 3-Methoxyhexane Ethoxy-2-heptene Propenyloxy benzene 5

6. Physical Properties of Ether
Physical properties of ethers
Boiling Points
The boiling points of ethers are lower than those of alcohols having the same molecular weights.
Solubility in water
compound
Formula MW
Bp (°C)
Ethanol
CH3-CH2-OH 46 78
Dimethyl ether
CH3-O-CH3
-25
Propane
CH3-CH2-CH3 44
-42
Ethers are much less soluble in water than alcohols. (Because they don’t have –OH group, So they are not hydrogen bond donors).
More water-soluble than hydrocarbons of similar molecular weight (Because they are polar)..

7. Preparation of Ethers
Dehydration of alcohols: The dehydration of alcohols takes place in the presence of acid catalysts (H2SO4, H3PO4) under controlled temperature (140 oC). The general reaction for ether formation is
Examples
symmetric ether

8. Preparation of Ethers 2)The Williamson synthesis
This method is usually used for preparation of unsymmetrical ethers

9. The alkoxide is commonly made by adding Na or K to the alcohol
Examples

10. Reactions Of Ethers Cleavage of ethers by hot concentrated acids
General equation:
Ethers are quite stable compounds.
Ethers react only under strongly acidic condition.
When ethers are heated in concentrated acid solutions, the ether linkage is broken
Specific example
The acids most often used in this reaction are HI, HBr, and HCl

11. If an excess of acid is present, the alcohol initially produced
is converted to alkyl halide thus the net products will be 2 moles of alkyl halide.
For example

12. Cyclic Ethers
In cyclic ethers (heterocyclic), one or more carbons are replaced with oxygen.
Epoxides are cyclic ethers in which the ether oxygen is part of a three-membered ring.
The simplest and most important epoxide is ethylene oxide.

13. 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.
Example

14. 1- Epoxides open in acidic solutions to form glycols.
Epoxides are much more reactive than common dialkyl ether this 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.

15. 2- Epoxides open in acidic alcohol solutions to form alkoxy alcohols
3- When an epoxide reacts with a hydrohalic acid ( HCl, HBr, or HI), a halide ion attacks the protonated epoxide to give halo alcohol .

16. 4- Reactions of Epoxides with Grignard and Organolithium Reagents to give longer alcohols
5- Ring opening of epoxides with amines

17. Exercise 1
Give a correct name for each of the following compounds.
Exercice 2
Propose a Williamson synthesis of 3-butoxy-1,1-dimethylcyclohexane from 3,3-dimethylcyclohexanol and butanol

18. Exercise 3
Predict the products of the following reactions:

19. Thank You for your kind attention !
Questions?