Which of the following experimental observations serve as distinct evidence for an mechanism? — Reaction Mechanism Chemistry Question

💡 Solution & Explanation

An $S_N2$ reaction exhibits second-order bimolecular kinetics (A is true). The required backside attack mandates a complete stereochemical inversion (B is true). Since it is a concerted reaction without a carbocation intermediate, rearrangements do not occur (C is false). Bulky substituents mechanically block the nucleophile's trajectory, severely dropping the reaction rate (D is true).