Question

Product A in the following reaction is

A.

B.

C.

D.

Answer 1

Hint: C₂H₄O is ethylene oxide. It is an epoxide. Epoxides are ethers having the oxygen atom in a three-membered ring. Epoxides are also called oxiranes. RMgI i.e, alkyl magnesium iodide called Grignard's reagent.

Complete Step by Step Solution:
- Ethylene oxide is a strained ring, it readily undergoes several additional reactions which result in ring-opening.
- RMgI is an organometallic compound. An organometallic compound is defined as a compound that contains a direct carbon-metal bond.
- RMgX is Grignard's reagent. It is prepared by the action of alkyl halides on magnesium metal in the presence of dry ether.
- The C-Mg bond in Grignard reagents is polar. The carbon atom is additionally electronegative than magnesium.
- The electrons of the C-Mg bond are attracted to the carbon atom. So, the carbon atom is partially negatively charged, and the magnesium atom has a partial positive charge.
- The alkyl groups in Grignard reagents are electron-rich and can work as nucleophiles.
- These alkyl groups would strike polar molecules at the area of insufficient electron density. Thus, Grignard reagents typically undergo nucleophilic substitution and nucleophilic addition reactions.
- In ethylene oxide, on the other hand, oxygen is much more electronegative than carbon or hydrogen.
- The C-O and O-H bonds are all polar. Grignard reagents are powerful nucleophiles and can react with the carbon atom of epoxides. The reaction results in ring-opening and the formation of alcohol.

This reaction happens in two steps.
Step-1
The attack of the RMgI on ethylene oxide leads to the formation of an additional product that is unstable.

Image: Formation of additional products.

Step-2
The additional product undergoes hydrolysis to form alcohol.

So, ethylene oxide in reaction with RMgI forms primary alcohol.
So, option A is correct.

Note: It must be noted that the ease of reaction of epoxide with RMgI increases with the increase in the ionic character of the C-Mg bond. In the preparation of Grignard reagents, a solution of the alkyl halide is dipped in dry ether into the reaction flask comprising magnesium ribbon suspended in dry ether. Dry ether is utilised as moisture may react with Grignard's reagent to form alkane. Thus, moisture or impurities discourage the yield of Grignard's reagent.