# Alkene Electrophilic Addition Reaction Stereoselectivity When Two New Asymmetric Centers Form

I had a question about the stereoselectivity in electrophilic addition reactions (specific to alkenes) that form additional asymmetric centers in their products. I understand that when a reactant with one preexisting asymmetric center forms a product with an additional asymmetric center, the two possible product stereoisomers are a pair of diastereomers because the configuration for the preexisting asymmetric center will stay the same while the configuration of the newly formed asymmetric center will vary. Since diastereomers differ in stability, their transition states differ as well, therefore the product with greater stability will come from a transition state with lower energy, which will require less activation energy to form. The product stereoisomer with greater stability therefore forms faster and becomes the predominant product. However, the textbook also says that the electrophilic addition reactions that form products with two additional asymmetric centers from a reactant without any asymmetric center form four stereoisomers of which two pairs are enantiomers with each other. It is also mentioned that this kind of reaction is not stereoselective. I don't understand how this is the case; the members that form enantiomers with each other might be energetically identical, but the stereoisomers that are diastereomers to each other must be energetically different, thus having different stability. If the logic from the first case applies the same here, wouldn't the reactions that form two new additional asymmetric centers also be stereoselective since they form diastereomers?