Asked in PMC Practice Test 28 (2021) 2021Moderate

Cyclic bromonium ion is formed when ethene reacts with:

Correct answer: C. Br2..

  • A. HBr.
  • B. HCL.
  • C. Br2..
  • D. None of these.

Explanation

When ethene reacts with bromine, the pi bond between the two carbon atoms is broken and the bromine molecule is added across the double bond. This results in the formation of a cyclic intermediate called a bromonium ion, which is a three-membered ring consisting of two carbon atoms and a positively charged bromine atom. The bromonium ion is a highly reactive intermediate that can undergo further reactions, such as nucleophilic attack by a negatively charged species, to form a product. The formation of a cyclic bromonium ion is an example of an electrophilic addition reaction.

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About Alkenes

Alkenes are unsaturated hydrocarbons containing a carbon-carbon double bond with sigma and pi components and restricted rotation. Their reactions include electrophilic addition of hydrogen, halogens, hydrogen halides and water, with Markovnikov orientation, oxidation, combustion and polymerisation, while their preparation commonly involves elimination from alkyl halides or alcohols.

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