Chapter 11.9: Reactions of Epoxides
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What is the stereochemistry of acid-catalyzed epoxide ring opening?
anti
What is the stereochemistry of nucleophilic epoxide ring opening?
Anti
Describe the mechanism behind the nucleophilic opening of an epoxide ring
Step 1: Make a new bond between a nucleophile and an electrophile and simultaneously break a bond to give stable molecules or ions • Backside attack of the nucleophile on the less hindered carbon of the highly strained epoxide opens the ring and displaces O- Step 2: Add a proton • Proton transfer completes the reaction
What is the regiochemistry of acid-catalyzed epoxide ring opening?
Markovnikov
What is the regiochemistry of nucleophilic epoxide ring opening?
less hindered carbon
Describe the mechanism behind acid-catalyzed hydrolysis of an epoxide
Step 1: Add a Proton • Proton transfer from the acid catalyst to oxygen of the epoxide gives a bridged oxonium ion intermediate Step 2: Make a New Bond Between a Nucleophile and an Electrophile and Simultaneously Break a Bond to Give Stable Molecules or Ions • Backside attack of H2O on the protonated epoxide opens the three-membered ring Step 3: Take a proton away • Proton transfer to solvent completes the formation of the glycol