What are cis and trans isomers also referred to as?

Cis and trans isomers are referred to as geometric isomers. This terminology is used to describe a specific type of stereoisomerism where the spatial arrangement of groups attached to a molecule differs based on their relative positions around a double bond or a ring system. In cis isomers, similar or identical groups are positioned on the same side, while in trans isomers, these groups are located on opposite sides.

Geometric isomerism arises primarily from a lack of rotation around a double bond or in cyclic structures, where the physical arrangement of substituents can lead to distinct physical and chemical properties. This contrasts with other types of isomers, such as structural isomers, which differ in the connectivity of atoms, and optical isomers (or enantiomers), which involve chiral molecules that are non-superimposable mirror images of each other. Understanding the concept of geometric isomers is crucial in organic chemistry, particularly in reactions and synthesis involving alkenes and cycloalkanes, as the configuration can significantly affect reactivity and properties.