See image — Reaction Mechanism Chemistry Question

💡 Solution & Explanation

Concept: When a Grignard reagent (CH3MgI) reacts with an ester, the mechanism proceeds in two stages. First, one equivalent of Grignard attacks the carbonyl of the ester to form a tetrahedral intermediate, which collapses by expelling the alkoxide (OCH3-) leaving group to form a ketone. Second, a second equivalent of Grignard attacks the newly formed ketone to give, after acidic workup, a tertiary alcohol. Reasoning: Dimethyl phthalate has TWO ester groups (-CO2CH3), each on the benzene ring at ortho positions. For each ester group: - Step 1: 1 mol CH3MgI attacks the ester carbonyl → tetrahedral intermediate collapses, losing -OCH3, forming a methyl ketone (acetyl group, -COCH3 on the ring). - Step 2: 1 mol CH3MgI attacks the ketone carbonyl → after H+ workup gives -C(CH3)2OH (a tertiary alcohol). So each ester group consumes 2 moles of CH3MgI. With 2 ester groups in dimethyl phthalate: Total CH3MgI consumed = 2 ester groups × 2 mol CH3MgI per ester = 4 mol CH3MgI. The product is the ortho-bis(2-hydroxy-2-propyl)benzene (each -CO2CH3 converted to -C(CH3)2OH), which matches the structure shown. Why other options fail: - (a) 2: Would only account for one addition per ester, stopping at the ketone stage — no tertiary alcohol formed. - (b) 3: Not chemically meaningful for this symmetric substrate. - (d) 5: Excess beyond what is stoichiometrically required; no additional reactive sites exist after both esters are converted. Therefore, the correct answer is C.