can anybody explain me mechanism of syn and anti addition?

can anybody explain me mechanism of syn and anti addition?


1 Answers

878 Points
13 years ago

Dear student,

If the two-step mechanism described above is correct, and if the carbocation intermediate is sufficiently long-lived to freely-rotate about the sigma-bond component of the original double bond, we would expect to find random or non-stereoselective addition in the products. On the other hand, if the intermediate is short-lived and factors such as steric hindrance or neighboring group interactions favor one side in the second step, then stereoselectivity in product formation is likely. The following table summarizes the results obtained from many studies, the formula HX refers to all the strong Brønsted acids. The interesting differences in stereoselectivity noted here provide further insight into the mechanisms of these addition reactions.

Reagent H–X X2 HO–X RS–Cl Hg(OAc)2 BH3
Stereoselectivity mixed anti anti anti anti syn


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