JEE Main · 2021 · 18 Mar 2021 · Shift 1 · Haloalkanes and Haloarenes

Alcoholic potassium hydroxide supplies ethoxide-rich conditions that strip a proton and a halide from adjacent carbons, so it is the reagent for $\beta$-elimination to an alkene. Palladium on barium sulphate, poisoned, is Lindlar's catalyst, which halts hydrogenation of an alkyne at the alkene. Benzene hexachloride comes from the photochemical addition of three chlorine molecules across the ring, an addition and not a substitution. Polyacetylene conducts along its conjugated chain and is used in battery electrodes. The pairing is alcoholic potassium hydroxide with $\beta$-elimination, $Pd/BaS{\mathrm{O}}_4$ with Lindlar's catalyst, benzene hexachloride with addition and polyacetylene with battery electrodes.