AP EAPCET 26 May 2025 Shift 1 Paper

Identify Z: Since Z undergoes nucleophilic substitution in two steps, it follows an $\mathrm{S_N1}$ mechanism, so Z must be a tertiary alkyl bromide.For the formula $\mathrm{C}_5\mathrm{H}_{11}\mathrm{Br}$, the tertiary bromide is 2-bromo-2-methylbutane, $\mathrm{(CH_3)_2C(Br)CH_2CH_3}$.Identify Y: HBr addition to Y gives this tertiary bromide by Markovnikov addition, so Y is 2-methylbut-2-ene, $\mathrm{(CH_3)_2C=CHCH_3}$.Identify X: Dehydration of X must give 2-methylbut-2-ene as the major product.The alcohol that directly gives this more substituted alkene is 2-methylbutan-2-ol, $\mathrm{(CH_3)_2C(OH)CH_2CH_3}$.Mechanism check: Z ionizes slowly to a tertiary carbocation and $\mathrm{Br^-}$, then the nucleophile attacks in a fast second step, confirming two-step $\mathrm{S_N1}$ substitution.Thus X is 2-methylbutan-2-ol and Y is 2-methylbut-2-ene, which corresponds to option option B.