Chemistry Question from JEE Main 2025 · 24 January, Shift 1

Following are the four molecules P, Q, R and S. Which one among the four molecules will react with H-Br(aq) at the fastest rate?

Here P and Q are six-membered cyclic ethers, each containing one ring oxygen: in P the $C=C$ double bond is not attached to the oxygen-bearing carbon, while in Q the double bond is directly attached to the ring oxygen. R is 1-methylcyclohexene, with a $CH_3$ group on one of the doubly bonded carbons, and S is 1,2-dimethylcyclohexene, with a $CH_3$ group on each of the doubly bonded carbons.