When cyclohexene reacts with bromine in presence of heat and UV light, the product is :

Question

Accepted Answer

When cyclohexene reacts with bromine in the presence of heat and UV light, the product is 3-Bromo Cyclohexene. Let's delve into the reasoning behind this and why the other options are incorrect.

1. **Explanation for Option 1: 3-Bromo Cyclohexene**
   - Cyclohexene is an unsaturated compound with a double bond. When it reacts with bromine under the influence of heat and UV light, a radical substitution reaction occurs. The UV light initiates the formation of bromine radicals, which then abstract a hydrogen atom from the allylic position (the position adjacent to the double bond) of cyclohexene. This results in the formation of a 3-bromo cyclohexene, where the bromine atom is added to the allylic position. This type of reaction is characteristic of allylic bromination, which is facilitated by the presence of heat and UV light.

2. **Why Option 2 is Incorrect: 1, 2-Dibromo Cyclohexane**
   - The formation of 1, 2-dibromo cyclohexane would typically occur through an addition reaction where bromine adds across the double bond of cyclohexene. However, this reaction does not require heat and UV light and is not the expected outcome under these conditions. The presence of heat and UV light favors radical substitution rather than addition.

3. **Why Option 3 is Incorrect: Bromo Cyclohexane**
   - Bromo cyclohexane would be the product if the double bond in cyclohexene were completely saturated with hydrogen, followed by substitution with bromine. However, this is not the case here. The reaction conditions (heat and UV light) favor allylic bromination rather than complete saturation and substitution.

4. **Why Option 4 is Incorrect: Bromo Benzene**
   - Bromo benzene is not a possible product from the reaction of cyclohexene with bromine. Cyclohexene is a six-membered ring with a double bond, not an aromatic compound like benzene. Therefore, the formation of bromo benzene is chemically impossible in this context.

In conclusion, the reaction of cyclohexene with bromine in the presence of heat and UV light leads to the formation of 3-bromo cyclohexene due to allylic bromination, making Option 1 the correct answer.