Isomerism: generating chemical variety

Abstract

This chapter explores the concept of isomerism—the joining together of identical groups of atoms to form different molecules. Structural isomers are molecules that have the same chemical composition but whose atoms are joined together in different ways. Stereoisomers possess the same atoms, which exhibit the same connectivities. However, stereoisomers exhibit different configurations. Stereoisomers fall into two groups: cis–trans isomers, and enantiomers. Cis–trans isomers are stereoisomers that possess groups of atoms locked in specific configurations, while enantiomers are non-superimposable mirror images of one another. Cis–trans isomerism is most common in molecules that possess one or more double bonds. The chapter describes the nomenclature used to differentiate isomers, including E/Z nomenclature and the use of Fischer projections. The chapter then looks at chirality in biological systems and why it is important, before considering the chemistry of isomers.