Q48E - Organic Chemistry (Mcmurry)

Question

What is the stereochemistry of the product from acid-catalyzed hydrolysis of trans-5,6-epoxydecane? How does the product differ from that formed in Problem 18-47?

Step-by-Step Solution

Answer

The stereochemistry of the product from acid-catalyzed hydrolysis of trans-5,6-epoxydecane is shown below:

In problem 18-47 the we got a racemic mixture but here a single product is formed.

Step 1: Ring opening reaction

5,6-epoxy-decane undergo ring opening reaction by acid hydrolysis. The oxygen of epoxide ring is protonation in case of aqueous acid. The OH group of water attack on it. The ${\text{SN}}^2$mechanism is used to epoxide ring opening. In the product OH groups will be trans to each other.

Step 2: Stereochemistry of product

The groups attached to epoxide rings are trans to each other one is below the plane and the other above the plane. Therefore, both the OH group are in the same plane but trans to each-other.

Stereochemistry of the product

Step 3: Difference in products

In problem 18-47 the product formed is a racemic mixture of R, R and S, S epoxidace but in this case only a single product is formed because both the bulky groups are trans to each-other therefore, no back side attack of nucleophile is possible.