Question

Reaction of cis-2-butene with m-chloroperoxybenzoic acid yields an epoxide different from that obtained by reaction of the trans isomer. Explain.

Short answer

Answer

The reaction of cis-2-butene and trans-2-Butene with m-chloroperoxybenzoic acid is,

Step-by-step solution

Step-by-Step SolutionStep 1: Alkene on reaction with peroxyacid

The alkene reacts with peroxyacid in a one-step and produces epoxide. The most commonly used peroxyacid is MCPBA (m-chloroperoxybenzoic acid).The cis-isomer forms cis product, and the trans isomer forms a mixture of enantiomers of trans product.

The reaction of cis-2-Butene with m-chloroperoxybenzoic acid

There is a syn addition of oxygen to a double bond when epoxidation is done using m-chloroperoxybenzoic acid (RCO₃H). The original bond stereochemistry is retained, and the product obtained is a meso compound. When alkene is a starting material, the methyl groups are cis in the epoxide product.

Formation of cis product

The reaction of trans-2-Butene with m-chloroperoxybenzoic acid

A trans product is obtained when trans-2-Butene reacts with m-chloroperoxybenzoic acid. The peroxyacid can attack either from the top or bottom of a double bond, forming a mixture of enantiomers.

Formation of trans product