Question

What is the major product of the reaction of an alkene with bromine water?

• A. Alkane
• B. Dibromoalkane
• C. Alcohol
• D. Bromoalkene

Hint:

In electrophilic addition reactions, alkenes undergo the addition of two atoms across the double bond. For alkenes with bromine, the result is a dibromoalkane.

Answer 1

The Correct Option is B

The reaction of an alkene with bromine water is a classic example of an electrophilic addition reaction. Here’s how the reaction proceeds:
1. Alkene Structure: - Alkenes contain a carbon-carbon double bond, which is rich in electrons and acts as a nucleophile. The pi-electrons of the double bond are highly reactive and can undergo a reaction with electrophiles. 2. Reaction with Bromine: - Bromine (\( \text{Br}_2 \)) is an electrophile. When it reacts with an alkene, the double bond breaks and forms a three-membered bromonium ion intermediate. This intermediate is unstable and quickly reacts with a bromide ion (\( \text{Br}^- \)) from the bromine water. - The bromide ion attacks the more stable carbon of the bromonium ion, leading to the formation of a dibromoalkane where two bromine atoms add to the carbon atoms that were previously involved in the double bond.
3. Major Product: - The major product of this reaction is a dibromoalkane, where the two bromine atoms add across the double bond. 4. Incorrect Options: - Option (1) "Alkane" is incorrect because the reaction does not involve hydrogenation (which would convert the alkene to an alkane). - Option (3) "Alcohol" is incorrect because alcohol formation requires a different reaction mechanism (such as hydration). - Option (4) "Bromoalkene" is incorrect because the reaction results in the addition of two bromine atoms, not just one.