When exactly one mole of 3-methylcyclohexene is fully reacted with an excess of liquid bromine in 1, — Hydrocarbons Chemistry Question
Question
When exactly one mole of 3-methylcyclohexene is fully reacted with an excess of liquid bromine in 1,2-dichloroethane in the dark, what is the total number of distinct dibromo stereoisomeric derivatives that can be theoretically isolated from the reaction mixture?
💡 Solution & Explanation
Bromination of 3-methylcyclohexene adds two $Br$ atoms *anti* to the double bond, forming 1,2-dibromo-3-methylcyclohexane. The addition creates two new chiral centers at C1 and C2, and C3 already holds a methyl group. Anti-addition restricts the relative stereochemistry of the bromines (they must be trans to each other). The methyl group at C3 can be either cis or trans relative to the C2 bromine. This gives rise to two diastereomeric pairs of enantiomers. Thus, 4 distinct stereoisomeric products are formed.