Determined syn8/31/2023 Those three reactions we’ll look at today are addition of HBr, bromination with Br 2, and hydrogenation with Pd-C and H 2. We’re going to look at three key reactions of alkenes and see how they each demonstrate a different pattern of stereochemistry in addition reactions. This post is about the second key theme in addition reactions of alkenes: stereochemistry. In the last post on alkene addition reactions, we discussed one of the two key themes to look for in addition reactions: regiochemistry (in other words – what is the favored direction in which the pi-bond breaks). A Collection Of Observations That Nobody Predicted Ahead Of Time Until They Did The Experiment Summary: Stereoselectivity In Alkene Addition Reactionsġ.Hydrogenation Of Alkenes With Pd-C And H 2 Is Selective For Addition Stereochemistry.Addition Of Bromine To Alkenes Is Stereoseletvie, Giving “Anti” Addition Stereochemistry.Addition Of H-Br To Alkenes Is Not Stereoselective, And Gives A Roughly Equal Mixture Of “Syn” And “Anti” Products.A Collection of Observations On Reaction Alkene Addition Stereochemistry That Nobody Predicted Ahead Of Time.An example of this is bromination with Br2 or chlorination with Cl2 In a second pattern, the addition reaction gives anti products. ![]() An example is the addition of H-Br to alkenes ![]() In one pattern, the addition reaction gives a mixture of syn and anti products.In addition to the regioselectivity of an addition reaction (often summarized by Markovnikov’s Rule) there are three important patterns for the stereoselectivity of reactions.To keep them all straight, it is helpful to divide them into families depending on the pattern of bonds that form and break. There are a large number of alkene addition reactions.Stereoselectivity In Alkene Addition Reactions: “Syn” vs “Anti”
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