Question

Griginard reagents react with oxetane, a four membered cyclic ether, to yield primary alcohols, but the reaction is much slower than the corresponding reaction with ethylene oxide. Suggest a reason for the difference in reactivity between oxetane and ethylene oxide.

Oxetane

Short answer

The difference in reactivity is due to the difference in ring strain.

Step-by-step solution

Cyclic compounds

The organic compounds that consist of a closed chain of hydrocarbons are called cyclic compounds.

The oxetane is a cyclic four-membered ring containing oxygen, and ethylene oxide is a cyclic three-membered ring containing oxygen.

Reaction of oxetane

The reaction of oxetane with the Grignard reagent followed by hydrolysis is shown below.

Reaction of ethylene oxide

The reaction of ethylene oxide with the Grignard reagent followed by hydrolysis is shown below.

The ethylene oxide is a compact and strained compound that undergoes cleavage easily to give the alcohol on reaction with RMgX than the oxetanes.

Hence, the difference in ring strain causes the difference in reactivity.