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An asymmetric oxidation is an oxidation that favours one stereochemical outcome, often by using a chiral catalyst. Asymmetric epoxidation and asymmetric dihydroxylation are examples: an oxygen-transfer process also creates controlled spatial structure.^[ref]

Oxidation state change and enantioselectivity describe different aspects of the result. A high chemical yield therefore does not by itself establish a high enantiomeric excess.

Enantioselectivity is preferential formation or reaction of one enantiomer over the other. For a product containing two enantiomers, their imbalance is commonly reported as enantiomeric excess, the absolute difference between their amounts divided by their sum.

A product ratio of $90:10$ corresponds to $80\%$ enantiomeric excess, not $90\%$. A chiral catalyst can make the competing transition states diastereomeric and therefore unequal in free energy. Selectivity depends on the full reaction conditions and must be distinguished from the separate question of overall chemical yield.

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 enantioselective, since site preference and handedness are independent questions.