Question

1, 2-dimethylcyclohexene is treated with $B{r}_2/CC{l}_4$. The product is

• A. Cis-1, 2-dibromo-1, 2-dimethylcyclohexane.
• B. Trans-1, 2-dibromo-1, 2-dimethylcyclohexane
• C. Both (a) and (b)
• D. 3-bromo-1, 2-dimethylcyclohexene

Answer 1

The correct option is B Trans-1, 2-dibromo-1, 2-dimethylcyclohexane

Addition of halogens to alkenes is an example of electrophilic addition reaction. It involves cyclic halonium ion formation.
Here, it forms cyclic bromonium ion. Then, the $B{r}^{-}$ will attack the carbon from the back of bromonium ion result in anti-addition of $B{r}_2$ to the alkene.
Thus, addition of $B{r}_2$ to alkenes is anti-addition.
Anti-addition to 1, 2-dimethylcyclohexene gives trans-1, 2-dibromo-1, 2-dimethyl cyclo hexane.