The hydroxy ketone shown is treated with an excess of methylmagnesium bromide in dry ether. How many moles of the Grignard reagent are consumed per mole of the compound (counting both acid-base and addition steps)?

Answer: A

4-Hydroxybutan-2-one has an acidic O-H group and a ketone. The Grignard reagent first deprotonates the alcohol (1 mol, releasing methane), then adds to the ketone C=O (1 mol) to give a tertiary alkoxide. Total consumption is 2 mol.

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