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JEE Main levelSingle correct optionDifficulty 2 of 3o2182

Assertion: In the hydroboration of a terminal alkene , boron attaches to the terminal carbon. Reason: Boron is less hindered at the terminal carbon, and in the four-centre transition state the carbon that carries more positive charge, the more substituted one, receives hydrogen.

  1. ABoth Assertion and Reason are true and the Reason is the correct explanation of the Assertion
  2. BBoth Assertion and Reason are true but the Reason is not the correct explanation of the Assertion
  3. CAssertion is true but Reason is false
  4. DAssertion is false but Reason is true

Answer: A

The boron atom (with its bulky substituents) prefers the less hindered terminal carbon. In the transition state the hydridic hydrogen goes to the carbon that can better bear partial positive charge. Both statements are true and the reason explains the assertion.
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