Answer: Dimethylformamide (DMF).
- A Water in the majority of cases studied
- B Ethanol as widely reported
- C Dimethylformamide (DMF)
- D Acetic acid in standard practice
Correct answer: C. Dimethylformamide (DMF)
Explanation: Polar aprotic solvents like DMF, DMSO, and acetone do not solvate the nucleophile strongly, leaving it more reactive and favouring SN2.
SN2 proceeds in a single step with backside attack and inversion of configuration, while SN1 forms a planar carbocation intermediate first, leading to racemisation.
Concept context
Study carbon-halogen compounds: how they are made, how they react via SN1/SN2 and elimination, their stereochemistry, and their environmental impact.