Question

Ethylene oxide when treated with Grignard reagent yields:
(A) Secondary alcohol
(B) Tertiary alcohol
(C) Cyclopropyl alcohol
(D) Primary alcohol

Answer 1

Hint: Ethylene oxide is a very reactive molecule and its C-O bond will get cleaved as nucleophilic carbon atom of Grignard reagent will attack on the electrophilic carbon atom of ethylene oxide. Ethylene oxide is also called oxirane.

Step by step answer:
- Ethylene oxide is also known by another name which is oxirane. We are taking the general Grignard reagent which is RMgX.
- Grignard reagents are a group of reagents, which are generated by reacting organic halides and magnesium metal (Mg) mostly in the presence of ether. They have the general formula RMgX. Here, R represents an organic group (alkyl or alkenyl) while X represents a halogen. They are applied in the Grignard reaction.
The reaction of Grignard reagent with ethylene oxide is represented below.

- We can see that the nucleophilic alkyl group of Grignard reagent will attack the electrophilic atom of ethylene oxide which is carbon. So, C-O bond of ethylene oxide will get broken and an organo-magnesium compound will form. Then, upon hydrolysis, we will get alcohol as a product.
- In the product molecule, the hydroxyl group is attached to a carbon that is bonded with other one carbon atom. So, we can say that alcohol is a primary alcohol.
Thus, we can conclude that Ethylene oxide reacts with Grignard reagent to give a primary alcohol.

So, option (D) is a correct answer.

Note: We should note that, when we are performing a reaction involving Grignard reagents, it is necessary to ensure that no water is present which would otherwise cause the reagent to decompose rapidly. Therefore, the majority of Grignard reactions occur in solvents such as anhydrous diethyl ether.