Methyl 7-hydroxy-4-oxoheptanoate, $HO - CH X_{2} - CH X_{2} - CH X_{2} - CO - CH X_{2} - CH X_{2} - COOCH X_{3}$ , is treated with a large excess of $CH X_{3} MgBr$ in dry ether, followed by $H X_{3} O X^{+}$ . Count the moles of $CH X_{3} MgBr$ consumed per mole of the compound. Assume the O-H group is simply deprotonated (giving methane), the ketone and the ester undergo nucleophilic addition only (an ester takes two equivalents), and there is no enolisation or cyclisation.

Numerical answer type, tolerance 0.5.

Answer: 4

The O-H group consumes 1 mole (acid-base, giving

CH X_{4}

). The ketone C=O adds 1 mole. The ester adds 2 moles (ketone intermediate, then tertiary alkoxide). Total = 1 + 1 + 2 = 4 moles.