Electrophilic additions to alkenes can be stereoselective

Although they really belong in Chapter 17 with other nucleophilic substitution reactions, we included the last few examples of epoxide-opening reactions here because they have many things in common with the reactions of bromonium ions. Now we are going to make the analogy work the other way when we look at the stereochemistry of the reactions of bromonium ions, and hence at the stereoselectivity of electrophilic additions to alkenes. We shall first remind you of an epoxide reaction from Chapter 17, where you saw this. 

Now we can move on to look at the stereochemistry of electrophilic addition to alkenes. 

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