Each enantiomer can react at different rates with a chiral reagent even when the reaction doesn’t create a new stereogenic centre. This is call kinetic resolution. Enzymes are particularly efficient at doing this. Lipases can form an ester from an alcohol, but where the alcohol has two enantiomers it is possible if the reaction is stopped at about half completion one enantiomer will have almost been entirely transformed into the ester whereas the other enantiomer will hardly have been converted at all.
