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JEE MAIN Chemistry QUESTION #1007
Question 1
RBr undergoes Grignard reaction (Mg, dry ether) followed by hydrolysis (\(\text{H}_2\text{O}\)) to give 2-methylbutane. The maximum number of structural isomers of RBr that can produce 2-methylbutane is:
  • 5
  • 4(Correct)
  • 3
  • 1
Correct Answer Explanation
2-Methylbutane is \(\text{CH}_3\text{CH(CH}_3\text{)CH}_2\text{CH}_3\). The Grignard reagent RMgBr reacts with water to give R–H. So R– must be a fragment of 2-methylbutane: 1-methylbutyl, 2-methylbutyl, 1-methyl-1-propyl, neopentyl, and isobutyl radicals. Counting distinct structural isomers of RBr gives 4.