Answer: Moisture or oxygen is present.
- A The solvent is dry ether
- B Excess Mg is used
- C Moisture or oxygen is present
- D The alkyl halide is primary
Correct answer: C. Moisture or oxygen is present
Explanation: Water destroys the Grignard reagent: RMgX + H₂O → RH + Mg(OH)X. Oxygen can also oxidise it. Strictly anhydrous, inert conditions are essential.
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.