Isomers z Isomers are molecules that have the same chemical formula but different structures z Stereoisomer differs in the 3-D orientation of atoms z Diastereomers are isomers with > 1 chiral center. – Pairs of isomers that have opposite configurations at one or more of the chiral centers but that are not mirror images of each other. z Epimers are a special type of diastereomer. – Stereoisomers with more than one chiral center which differ in chirality at only one chiral center. – A chemical reaction which causes a change in chirality at one one of many chiral center is called an epimerisation.Isomers z Isomers are molecules that have the same chemical formula but different structures z Stereoisomer differs in the 3-D orientation of atoms z Diastereomers are isomers with > 1 chiral center. – Pairs of isomers that have opposite configurations at one or more of the chiral centers but that are not mirror images of each other. z Epimers are a special type of diastereomer. – Stereoisomers with more than one chiral center which differ in chirality at only one chiral center. – A chemical reaction which causes a change in chirality at one one of many chiral center is called an epimerisation