Question

Identify ‘Y’?

Answer 1

The correct answer is (b).

Explanation:

Step 1. Grignard reaction

I m guessing that the starred `"O"` in your starting material is a radio-labelled oxygen atom.

The first step in the formation of `"X"` is the Grignard reaction of a lactone (a cyclic ester) to give a tertiary alcohol and a phenol.

• The Grignard reagent first converts the lactone to a phenyl ketone.

• A second mole of the reagent then adds to the ketone to form a tertiary alcohol after acid workup.

• The labelled oxygen remains on the original phenyl group.

Step 2. Acid-catalyzed formation of an ether

The formation of `"Y"` involves the acid-catalyzed condensation of a phenol and an alcohol to form an ether.

The steps in the mechanism are:

• Sulfuric acid protonates the alcohol and converts it into a better leaving group.

• The phenol displaces a water molecule from the water molecule and forms a protonated ether.

• A molecule of excess alcohol deprotonates the ether

Again, note that the phenol oxygen stays attached to the ring.

Thus, we can represent the formation of `"Y"` as