Question

The mechanism of the following reaction involves the formation of a .......... membered ring. 

Hint:

In a Wittig reaction, a phosphonium ylide reacts with a carbonyl compound to form an alkene and a 6-membered ring intermediate.

Answer 1

Correct Answer: 4

The reaction depicted is a Wittig reaction, a classic reaction in organic chemistry where a carbonyl compound is converted into an alkene through the formation of a ring intermediate.

1. Identify the reactants: The reaction involves cyclohexanone and a Wittig reagent, Ph₃P=CH₂.

2. Examine the mechanism: The Wittig reaction mechanism involves the formation of an oxaphosphetane intermediate, a four-membered ring.

3. Ring formation: In this reaction, the oxygen from the carbonyl and the phosphorus from the Wittig reagent form bonds creating a cyclic intermediate.

4. Intermediate breakdown: The oxaphosphetane collapses to give the final alkene and triphenylphosphine oxide.

5. Verify ring size: The intermediate formed is indeed a four-membered ring, consistent with the range provided: 4.

Conclusion: The mechanism of the reaction involves the formation of a 4-membered ring.