MHTCET 13 Apr 2026 Shift 2 Paper

Concept:The rate of an $S_{\mathrm{N}}1$ reaction depends on the stability of the carbocation intermediate formed during the reaction.Explanation:In $S_{\mathrm{N}}1$ reactions, the slow and rate-determining step is the formation of a carbocation.$$R-X \rightarrow R^+ + X^-$$Bulky alkyl groups on the carbon attached to the halogen stabilize the carbocation through the $+I$ effect and hyperconjugation.Tertiary alkyl halides, which have bulky groups, form highly stable tertiary carbocations.The reactivity order for $S_{\mathrm{N}}1$ is:$$3^\circ > 2^\circ > 1^\circ$$Thus, bulky alkyl groups favor $S_{\mathrm{N}}1$ reactions.Strong nucleophiles favor $S_{\mathrm{N}}2$ reactions, not $S_{\mathrm{N}}1$.Non-polar solvents do not stabilize ionic intermediates, whereas $S_{\mathrm{N}}1$ requires a polar solvent.Small alkyl groups give less stable carbocations, so they do not favor $S_{\mathrm{N}}1$.Answer:Option C: Bulky alkyl groups on the carbon atom attached to halogen atom.