Chapter 13.8, Problem 3LTS

Interpretation Introduction

Interpretation: Starting material and reagents required to prepare the given epoxide need to be identified.

  

Concept introduction:

Preparation of epoxide- Epoxides can be prepared via two methods, one with peroxy acids and the other with halohydrins.

Alkenes are starting material in the preparation of epoxides with peroxy acids. Here, the general reaction is represented as follows:

  

Peroxy acids generally used in this process are MCPBA and peroxyacetic acid. The formation of epoxide via peroxy acid is a stereospecific process; thus, cis substituents in alkene (starting material) remain at cis to each other in the epoxide (product). Similarly, trans substituents in alkene remain at trans to each other.

The preparation of epoxides from halohydrins can simply take place upon treatment with a strong base. Here, halohydrin can be formed from alkene after treatment with a halogen in the presence of water.

The reactions involved in the preparation are as follows

  

  

The above reaction takes place via intramolecular Williamson ether synthesis. This is an S_N2-like process where an alkoxide ion acts as a nucleophile. This is also a stereospecific process.