Question

Draw the major product formed when the following epoxide reacts with aqueous acid. Use wedge/dash bonds, including H\'s at each stereogenic center, to show the stereochemistry of the product.

Answer 1

Concepts and reason

Epoxides are cyclic ethers with three membered cyclic rings. Epoxides are more reactive due to the presence of ring strain in three membered rings. Epoxide can undergo ring opening reaction in the presence of acidic or basic conditions. The lone pair of electrons present in oxygen atoms can abstract the proton followed by the attack of nucleophile on a carbon atom of epoxide ring which gives an addition product.

Fundamentals

The basic structure epoxide contains oxygen atom bonded to the two adjacent carbons of hydrocarbon chain.

Ring opening reaction of epoxides: Epoxides ring opens under acidic as well as basic conditions.

Example:

The resonance structures are given below:

Notice that structure-I is more stable due to presence of more stable tertiary carbocation.

The mechanism for the direction of attack of nucleophile is given below:

Hence, the nucleophile (water) attacks regioselectively from the backside of the plane containing epoxide ring and generates anti-diols.

Ans:

The major product formed when the following epoxide reacts with aqueous acid is given below:

Answer 2

Concepts and reason

Epoxides are cyclic ethers with three membered cyclic rings. Epoxides are more reactive due to the presence of ring strain in three membered rings. Epoxide can undergo ring opening reaction in the presence of acidic or basic conditions. The lone pair of electrons present in oxygen atoms can abstract the proton followed by the attack of nucleophile on a carbon atom of epoxide ring which gives an addition product.

Fundamentals

The basic structure epoxide contains oxygen atom bonded to the two adjacent carbons of hydrocarbon chain.

Ring opening reaction of epoxides: Epoxides ring opens under acidic as well as basic conditions.

Example:

The resonance structures are given below:

Notice that structure-I is more stable due to presence of more stable tertiary carbocation.

The mechanism for the direction of attack of nucleophile is given below:

Hence, the nucleophile (water) attacks regioselectively from the backside of the plane containing epoxide ring and generates anti-diols.

Ans:

The major product formed when the following epoxide reacts with aqueous acid is given below: