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How many alkyl halides (including all stereoisomers) on reaction with Mg in dry ether, followed by treatment with H+ / H2O, yield 2-methylbutane as the product?
- 4
- 5
- 6
- 8
Correct answer: 4
Solution
Protonolysis of a Grignard reagent simply replaces MgX with H, restoring the alkyl group. So the alkyl halide must have the same carbon skeleton as 2-methylbutane. Enumerate all unique positions for the halide in the 2-methylbutane framework and count stereoisomers at chiral centers.
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