= Regioselectivity
<Regioselectivity> is preferential reaction at one of several constitutionally distinct sites or orientations. It concerns which bonds form where, rather than the configuration of the resulting stereocenters.
For example, adding a reagent across an unsymmetrical <alkene> can place its two components in either orientation, producing different constitutional isomers. Electronic effects, steric interactions, and the catalyst determine the product ratio. A reaction can be strongly regioselective but weakly <enantioselectivity>[enantioselective], since site preference and handedness are independent questions.
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