Challenge Your Exam Readiness With Our Free DAT Practice Questions

SN1S_N1 rate depends primarily on carbocation stability because the rate-determining step is ionization to form a carbocation. Tertiary carbocations are strongly stabilized by hyperconjugation and inductive effects, making tert-butyl chloride exceptionally fast for SN1S_N1, especially in polar protic solvents like methanol that stabilize ions. Primary substrates (A, C, D) form unstable carbocations and thus are disfavored for SN1S_N1; they typically react via SN2S_N2 under appropriate conditions. While benzyl and allyl halides are also very reactive in SN1S_N1 due to resonance stabilization, none are listed here. Methanol enhances SN1S_N1 by solvating the leaving group and the carbocation intermediate. Additionally, a good leaving group (Cl⁻) supports ionization. Therefore, tertiary > secondary » primary ≈ methyl for SN1S_N1. Recognizing solvent effects and carbocation stability trends is a staple of DAT organic chemistry: tertiary substrates in protic media generally dominate SN1S_N1 reactivity.