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Chapter 18. Ethers and Epoxides; Thiols and Sulfides. Ethers. Definition: Two organic groups bonded to the same oxygen atom Examples:. Diethyl ether. Methyl phenyl ether (Anisole). Tetrahydrofuran (cyclic ether). Naming of Ethers. There are two ways to name it:

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Chapter 18

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Chapter 18 l.jpg

Chapter 18

Ethers and Epoxides;

Thiols and Sulfides


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Ethers

  • Definition: Two organic groups bonded to the same oxygen atom

  • Examples:

Diethyl ether


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Methyl phenyl ether (Anisole)

Tetrahydrofuran (cyclic ether)


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Naming of Ethers

There are two ways to name it:

  • Identifying the two organic substituents and adding the word ether

Dimethyl ether


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Tert-Butyl methyl ether

Ethyl-phenyl ether


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  • If other functional groups are present, the ether part is considered an alkoxy substituent.

Tert-butoxy butane

Para-ethoxy methoxy benzene


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1-methoxy-cyclohexene

4-tert-Butoxy-1-cyclohexene


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Isopropoxy cyclohexane

p-dimethoxybenzene


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  • Physical Properties

  • Soluble in water

  • Boiling point: very low, about 200C

  • R—O—R bonds: tetrahedral bond angle

  • The Oxygen atom is sp3-hybridized


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Preparation of Ethers


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Symmetrical ethers R-O-R


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Mechanism:


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Examples


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Symmetrical ethersR-O-R’

  • The Williamson Ether Synthesis:


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Examples

α-D-Glucose

Α-D-Glucose pentamethyl ether


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tert-Butoxide ion

Iodomethane

tert-Butyl methyl ether


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Methoxide ion

2-Chloro-2-methylpropane

2-Methylpropene


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1) Reaction

  • Alkoxymercuration of Alkenes


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2. Mechanism


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3. Examples

Styrene

1-Methoxy-1-phenyethane


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Reaction of Ethers


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  • Acidic Cleavage

    1) Ethers with primary and secondary alkyl groups react by an SN2

Ethyl isopropyl ether

Isopropyl alcohol

Iodoethane


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Mechanism


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Examples:

Bromoethane

Ethyl phenyl ether

Phenol

2-Ethoxypropanoic acid

Iodoethane

Lactic acid


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2) Ethers with a tertiary, benzylic, or allylic group react by an SN1 or E1

E1 reaction

tert-Butyl cyclohexyl ether

Cyclohexanol

2-Methylpropene


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Mechanism:


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SN1 reaction


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Mechanism:


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1) Claisen rearrangement is pecific to allyl aryl ethers, Ar-O-CH2CH=CH2

  • Claisen Rearrangement

2) Example:

Phenol

Sodium phenoxide

Allyl phenyl ether

Allyl phenyl ether

0-Allylphenol


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3) Mechanism:

Transition state


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sECTION 18.7


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SECTION 18.8


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SECTION 18.9


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SECTION 18.10


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