Methyl 4-oxopentanoate, CH3-CO-CH2-CH2-COOCH3, is treated with excess CH3MgBr in dry ether followed by H3O+. The main product is

JEE Advanced levelSingle correct optionDifficulty 3 of 3hx181

Methyl 4-oxopentanoate, $CH X_{3} - CO - CH X_{2} - CH X_{2} - COOCH X_{3}$ , is treated with excess $CH X_{3} MgBr$ in dry ether followed by $H X_{3} O X^{+}$ . The main product is

The ketone takes one

CH X_{3} MgBr

to give a tertiary alkoxide carbon bearing two methyls (

C (CH X_{3}) X_{2} OH

end). The ester takes two equivalents (via a ketone) to give a second

C (CH X_{3}) X_{2} OH

end. The product is

(CH X_{3}) X_{2} C (OH) CH X_{2} CH X_{2} C (OH) (CH X_{3}) X_{2}

, using 3 mol of Grignard reagent.