JEE Main · 2020 · 03 Sep 2020 · Shift 1 · Haloalkanes and Haloarenes

An ${\mathrm{S}}_{\mathrm{N}}1$ reaction goes through a carbocation formed in the slow step, with the nucleophile entering only afterwards. Because that rate-determining step does not involve the nucleophile, even weak nucleophiles serve, so (a) holds; bulkier groups relieve their crowding and stabilise the cation as it forms, making ${\mathrm{R}}^{\oplus }$ easier to produce, so (b) holds; and the flat carbocation is attacked from either face, giving both configurations and hence racemisation, so (c) holds. Only the claim about non-polar solvents is wrong, since ${\mathrm{S}}_{\mathrm{N}}1$ is in fact favoured by polar solvents that stabilise the ionic intermediate. The correct observations are (a), (b) and (c).