Identify the major product formed when the given compound is treated with concentrated H ₂ SO ₄ .

Step-by-step solution

The given starting material is 6-ethyl-3-ethylidene-3,4-dihydro-2H-pyran. When treated with concentrated H ₂ SO ₄ , it undergoes an acid-catalyzed ring opening followed by rearrangement and intramolecular aldol condensation to form a cyclohexenone derivative. Protonation of the enol ether double bond at C5 generates an oxocarbenium ion at C6, which undergoes hydrolysis (with trace water present or during workup) to open the pyran ring. This yields an intermediate allylic alcohol with a ketone group: HO-CH ₂ -C(=CH-