Question

classify each addition as either syn or anti.
rxn i
rxn ii
a. syn anti
b. syn syn
c. anti anti
d. anti syn

Explanation:

• For Rxn I: In the addition of \(Br_2\) to an alkene, the mechanism involves the formation of a bromonium ion intermediate. The second - bromide ion attacks from the opposite face of the bromonium ion. In the given product of Rxn I, the two \(Br\) atoms are on opposite faces of the cyclo - pentane ring (one \(Br\) is on a wedge and the other is on a dash), which is characteristic of an anti - addition.
• For Rxn II: In the addition of \(HBr\) to an alkene (in the absence of peroxides, following Markovnikov's rule), the addition is not a concerted process. However, the addition of \(H\) and \(Br\) (in the product, the \(H\) and \(Br\) are on the same side of the plane of the carbon - carbon double bond in terms of their relative orientation with respect to the other substituents. The \(H\) and \(Br\) addition is syn - like as they add to the same face of the alkene (when considering the orientation of the substituents \(Cl\), \(Me\), \(Et\) etc. around the carbon atoms where addition occurs).

Answer:

D. anti, syn