Benzoyl chloride is treated with excess $\mathrm{C}{}_2\mathrm{H}{}_5\mathrm{MgBr}$ and then $\mathrm{H}{}_3\mathrm{O}{}^{+}$. The final product is

The first $\mathrm{C}{}_2\mathrm{H}{}_5\mathrm{MgBr}$ gives 1-phenylpropan-1-one with loss of $\mathrm{MgBrCl}$. The ketone is more electrophilic than an ester and cannot be isolated, so a second mole adds, giving $\mathrm{C}{}_6\mathrm{H}{}_5-\mathrm{C}(\mathrm{C}{}_2\mathrm{H}{}_5){}_2-\mathrm{OMgBr}$. Hydrolysis gives 3-phenylpentan-3-ol.