Return to Contents Chapter 16: Ethers, Epoxides and Sulfides Ch 16 contents

SN1 type Reactions of Epoxides

SN1 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 that is weaker resulting in carbocation character at that more substituted C and the nucleophile attacks there....

Stereochemistry ? Because the C-O bond is not totally broken when the nucleophile attacks, the nucleophile still attacks at 180o with respect to the leaving group so there is still inversion at that center.

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organic chemistry © Dr. Ian Hunt, Department of Chemistry University of Calgary