Benzene (shown) is treated with 1-chloropropane and $\mathrm{AlCl}{}_3$; the major alkylbenzene formed is then brominated with $\mathrm{Br}{}_2$ and $\mathrm{FeBr}{}_3$. Which structure is the major final product?

In the Friedel-Crafts step the primary carbocation-like complex rearranges by a hydride shift to the isopropyl cation, so the major alkylbenzene is isopropylbenzene (cumene) rather than propylbenzene. The isopropyl group is activating and ortho/para-directing, and its bulk disfavours the ortho position. Bromination gives 1-bromo-4-isopropylbenzene as the major product.