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Chapter 16: Ethers, Epoxides and Sulfides



Summary | Ethers | Preparations of Ethers | Reactions of Ethers | Epoxides | Preparation of Epoxides | Reactions of Epoxides | Spectroscopic Analysis of Ethers | Sulfides | Self Assessment | Quiz |


Reactions of Epoxides

Chapter 16: Ethers, Epoxides and Sulfides

Overview of the Reactions of Epoxides

ring opening eactions of epoxides
Reaction type:  Nucleophilic Substitution

Summary

Depending on the reactivity of the nucleophile, there are two possible general scenarios:
epoxides with strong nucleophiles
epoxides with weak nucleophiles

SN2 type Reactions of Epoxides

S<sub>N</sub>2 type ring opening reaction of epoxides
Reaction type:  Nucleophilic Substitution (SN2)
Scenario 1:
The Nu attacks the more substituted C of the epoxide at 180o to the C-O bond that breaks.
which pathway occurs ?
Scenario 2:
The Nu attacks the least hindered end of the epoxide at 180o to the C-O bond that breaks.
Summary

SN1 type Reactions of Epoxides

S<sub>N</sub>1 like ring opening reactions of epoxides
Reaction type:  Nucleophilic Substitution (SN1 like)
Scenario 1:
The Nu attacks the more substituted C of the epoxide at 180o to the C-O bond that breaks.
which pathway occurs ?
Scenario 2:
The Nu attacks the least hindered end of the epoxide at 180o to the C-O bond that breaks.
consider the possible carbocations
one of the C-O bonds weakens In reality it is usually that the epoxide C-O bond to the more substituted center is weaker resulting in carbocation character at that C and the nucleophile attacks there.... because the C-O bond is not totally broken when the nucleophile attacks, it still attacks at 180o with respect to the leaving group.
Summary

 

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