Chapter 13, Problem 66IP

(a)

Interpretation Introduction

Interpretation:

The reagents that used to form the given epoxide from the allylic alcohol has to be identified.

Concept introduction:

Epoxides from Peroxy acids:

The commonly used Peroxy acids are meta-Chloroperoxybenzoic acid (MCPBA) and Peroxyacetic acid. This process is stereospecific.

If the substituent are cis to each other in the alkene, then it will remains cis to each other in Epoxide, and if the substituent are trans to each other in the alkene, then it will remains trans to each other in Epoxide.

(b)

Interpretation Introduction

Interpretation:

The plausible mechanism for the formation of the given orthoester from the epoxide has to be given.

Concept introduction:

Ring-opening of epoxide: The epoxide ring is highly strain and readily undergoes reaction with strong nucleophile result in the ring-opening reaction.

Acid-catalyzed ring-opening of epoxide: The epoxide ring is protonated and the nucleophile attack depends on the electronic or steric effect (nature of epoxide).

Regiochemistry: when the epoxide is unsymmetrical, the nucleophile attack at the more substituted position of the protonated epoxide ring.

Stereochemistry: when the nucleophile attack takes place at chiral center, an inversion of configuration is obtained.