Ethyl 4-oxopentanoate is subjected to the following sequence of reactions: (i) Ethylene glycol, dry HCl (ii) Excess CH₃MgBr (iii) H₃O^+ The major product formed is:

Step-by-step solution

The starting material is ethyl 4-oxopentanoate ( CH₃-CO-CH₂-CH₂-COOCH₂CH₃ ). Step (i): Reaction with ethylene glycol and dry HCl selectively protects the ketone group by forming a cyclic acetal (1,3-dioxolane derivative). The ester group remains unreactive under these conditions. Step (ii): The protected compound is treated with excess CH₃MgBr . The Grignard reagent reacts with the ester group. Two equivalents of CH₃MgBr are consumed by the ester to form a tertiary alkoxide ( -C(O^-MgBr^+)(CH₃)₂ ). Step (iii): Acid