Q22E - Organic Chemistry (Mcmurry)

Question

Treatment of the following alkene with a peroxy acid yields an epoxide different from that obtained by reaction with aqueous Br₂ followed by base treatment. Propose structures for the two epoxides, and explain the result.

Step-by-Step Solution

Answer

On reaction with peroxyacid epoxide formed from lower side and in presence of Br₂ epoxide formed at upper side as shown below:

Step 1: Treatment of the alkene with the peroxyacid

On the reaction of an alkene with peroxy acid (RCO₃H) leads to the formation of an epoxide.

The attack of the peroxide is from the lower side not from the upper because of the presence of the two methyl groups on the upper side which hindered the reaction to occur from the upper side as the attack from lower side leads to the formation of epoxide as shown below:

Step 2: Treatment of the alkene with the Br 2

As per the reaction with  Br₂  the attack of the bromine ion is from the lower side because the upper side is hindered by two methyl groups and at one carbon formation of hydroxy group occur and at other addition of Br ion occur then followed by base the abstraction of the proton occurs from the hydroxy group and formation of occurring which form the epoxide by attacking adjacent carbon and removal of Br ion so that now epoxide formation occurs from the upper side as shown below: