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Two reaction sequences are proposed to synthesize p -bromostyrene from ethylbenzene. Sequence A: (i) Br ₂/ FeBr ₃ (ii) Cl ₂/h (iii) alc. KOH, Sequence B: (i) Cl ₂/h (ii) alc. KOH, (iii) Br ₂/ FeBr ₃ Given below are two statements regarding these sequences: Statement I: Sequence B is an incorrect route because the final bromination step ( Br ₂/ FeBr ₃ ) will primarily result in electrophilic addition to the vinyl grou

Options

  1. AStatement I is correct but Statement II is incorrect
  2. BStatement I is incorrect but Statement II is correct
  3. CBoth Statement I and Statement II are correct
  4. DBoth Statement I and Statement II are incorrect

Correct answer

C. Both Statement I and Statement II are correct

Step-by-step solution

In Sequence B, the first two steps convert the ethyl group into a vinyl group, forming styrene. When styrene is subjected to Br ₂/ FeBr ₃ , the highly reactive carbon-carbon double bond undergoes rapid electrophilic addition of bromine, which outcompetes the desired electrophilic aromatic substitution on the ring. Thus, Sequence B fails to produce p -bromostyrene. In Sequence A, the aromatic ring is brominated first. The ethyl group is an activating, ortho/para directing group that does not react with Br ₂/ FeBr ₃

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