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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3o4203

For the reaction of a secondary alkyl bromide with a strong base in ethanol, which observations point to an E2 mechanism rather than E1?

  1. AThe rate increases in direct proportion to the concentration of base.
  2. BReplacing the beta-hydrogens by deuterium lowers the rate with .
  3. CSome of the alkene formed has a rearranged carbon skeleton.
  4. DThe more substituted alkene is the major product.

Answer: A, B

E2 rate depends on the base and shows a primary isotope effect because C-H breaks in the slow step. Rearranged skeletons indicate a carbocation (E1) and so go against E2. Saytzeff orientation is found in both E1 and E2 and does not discriminate. Only statements 1 and 2 are correct.
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