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Organic Chemistry , 6 th Edition L. G. Wade, Jr. Chapter 14 Ethers, Epoxides, and Sulfides. =>. Introduction. Formula R-O-R ¢ where R and R ¢ are alkyl or aryl. Symmetrical or unsymmetrical Examples:. =>. Structure and Polarity. Bent molecular geometry Oxygen is sp 3 hybridized - PowerPoint PPT Presentation
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Chapter 14 Ethers, Epoxides,
and Sulfides
Organic Chemistry, 6th EditionL. G. Wade, Jr.
Chapter 14 2
Introduction• Formula R-O-R where R and R are
alkyl or aryl.• Symmetrical or unsymmetrical• Examples:
O CH3
CH3 O CH3 O
=>
Chapter 14 3
Structure and Polarity• Bent molecular geometry• Oxygen is sp3 hybridized• Tetrahedral angle
=>
Chapter 14 4
Boiling PointsSimilar to alkanes of comparable molecular weight.
=>
Chapter 14 5
Hydrogen Bond Acceptor• Ethers cannot H-bond
to each other.• In the presence of
-OH or -NH (donor), the lone pair of electrons from ether forms a hydrogen bond with the -OH or -NH.
=>
Chapter 14 6
Solvent Properties
• Nonpolar solutes dissolve better in ether than in alcohol.
• Ether has large dipole moment, so polar solutes also dissolve.
• Ethers solvate cations. • Ethers do not react with
strong bases. =>
Chapter 14 7
Ether Complexes
• Grignard reagents
• Electrophiles
• Crown ethers
O B
H
H
H
+ _
BH3 THF
=>
Chapter 14 8
Common Names of Ethers
• Alkyl alkyl ether• Current rule: alphabetical order• Old rule: order of increasing complexity• Symmetrical: use dialkyl, or just alkyl.• Examples:
CH3CH2 O CH2CH3
diethyl ether orethyl ether
CH3 O C
CH3
CH3
CH3
t-butyl methyl ether ormethyl t-butyl ether =>
Chapter 14 9
IUPAC Names
• Alkoxy alkane• Examples:
CH3 O C
CH3
CH3
CH3
2-methyl-2-methoxypropane
O CH3
Methoxycyclohexane
=>
Chapter 14 10
Williamson Synthesis
• Alkoxide ion + 1 alkyl bromide (or tosylate)• Example:
CH3 O H
CH3
CH3
+ K CH3 O
CH3
CH3
_K+
CH3 O
CH3
CH3
_+ CH3CH2 C
H
H
Br CH3 O
CH3
CH3
CH2CH2CH3 + Br_
=>
Chapter 14 11
Phenyl Ethers
• Phenoxide ions are easily produced for use in the Williamson synthesis.
• Phenyl halides or tosylates cannot be used in this synthesis method.
O H
+ NaOH
O_
Na+
+ HOH
=>
Chapter 14 12
Cleavage of Ethers
• Ethers are unreactive toward base, but protonated ethers can undergo substitution reactions with strong acids.
• Alcohol leaving group is replaced by a halide.
• Reactivity: HI > HBr >> HCl
=>
Chapter 14 13
Mechanism for Cleavage
CH3 O CH3 H Br CH3 O CH3
H_
Br_
++
Br_ +CH3 O CH3
H
Br CH3 + H O CH3
• Ether is protonated.
• Alcohol leaves as halide attacks.
• Alcohol is protonated, halide attacks, and another molecule of alkyl bromide is formed. =>
Chapter 14 14
Phenyl Ether Cleavage
• Phenol cannot react further to become halide.
• Example:
O CH2CH3HBr
OH
+ CH3CH2 Br
=>
Chapter 14 15
End of Chapter 14
