The intense competition between bimolecular substitution and bimolecular elimination is strongly inf — Haloalkanes and Haloarenes Chemistry Question

💡 Solution & Explanation

A) True. Secondary substrates are somewhat sterically crowded. When reacting with strong bases/nucleophiles like methoxide, $E2$ elimination becomes the major pathway because abstracting an exposed peripheral $\beta$ -proton is kinetically much easier than penetrating the steric shield for a backside $S_N2$ attack. B) True. Bulky bases like $t-BuO^-$ are physically too massive to perform $S_N2$ backside attacks and therefore act exclusively as bases, driving $E2$ elimination. Due to their extreme bulk, they are forced to abstract the most accessible peripheral proton, usually yielding the less substituted Hofmann product. C) True. Reagents like $I^-$ and $HS^-$ are large, highly polarizable, and very fast nucleophiles but are extremely weak bases (conjugate bases of very strong acids). They readily perform $S_N2$ attacks but cannot thermodynamically abstract protons, effectively suppressing E2. D) False. Cyanide ($CN^-$) is relatively small, an excellent nucleophile, and a weak base, powerfully favouring classic $S_N2$ substitution.