Consider the following two nucleophilic substitution reactions involving optically active substrates: Reaction I: Optically active 2-chlorobutane is treated with NaI in dry acetone. Reaction II: Optically active 3-bromo-3-methylhexane undergoes solvolysis in water. What is the stereochemical nature of the major products formed in Reaction I and Reaction II, respectively?

Step-by-step solution

Reaction I involves a secondary alkyl halide (2-chlorobutane) reacting with a good nucleophile ( I ⁻ ) in a polar aprotic solvent (dry acetone). These conditions strongly favor the S _ N 2 mechanism. The S _ N 2 mechanism proceeds via a concerted backside attack, resulting in the inversion of configuration. Reaction II involves a tertiary alkyl halide (3-bromo-3-methylhexane) reacting in a polar protic solvent (water), which also acts as a weak nucleophile. These conditions strongly favor the S _ N 1 mechanism. The