Question

1) Draw the arrow pushing mechanism for the bromination of cyclohexene.

2) If this reaction was done using Br₂in DCM, what product would you expect (show stereochemistry)?

Answer 1

1) Given below is the mechanism of the electrophilic addition reaction between cyclohexene and Br2. The first step is pi-electron of cyclohexene attacks on to the Br of BR2 molecule. The lone pair of Br then attacks on the other side on C=C bond. This is a concerted mechanism. Formation of a cyclic bromonium ion intermediate occurs. This is then attacked by the nucleophilic Br- in solution to give dibromocyclohexane product.

2) If the reaction is done using Br2 in DCM, we will get anti-stereochemistry of the two Br groups with each other.