JEE Main · 2023 · 30 Jan 2023 · Shift 1 · Hydrocarbons

The alkene supplied is 2-methylpropene. With cold sulphuric acid the proton adds to the terminal $\mathrm{C}{\mathrm{H}}_2$ and the hydrogen sulphate ion adds to the resulting tertiary carbocation, giving tert-butyl hydrogen sulphate, $(\mathrm{C}{\mathrm{H}}_3{)}_3\mathrm{C}-\mathrm{OS}{\mathrm{O}}_3\mathrm{H}$, as the first product. On warming with sulphuric acid near $80^{\circ }\mathrm{C}$ the tertiary carbocation instead adds to a second molecule of the alkene and then loses a proton, so two units of 2-methylpropene join to form the dimer 2,4,4-trimethylpent-2-ene as the second product. The products are tert-butyl hydrogen sulphate and 2,4,4-trimethylpent-2-ene respectively.