What characterizes a Z-isomer?

A Z-isomer, often referred to in the context of geometric isomerism, is characterized by having substituents on the same side of a double bond or a ring structure. This term comes from the German 'zusammen,' meaning 'together.' In the context of alkenes, if the higher priority groups (assigned according to Cahn-Ingold-Prelog priority rules) are on the same side of the double bond, the configuration is designated as Z.

Understanding this helps differentiate it from E-isomers, where the highest priority groups are situated on opposite sides of the double bond. Therefore, for geometric isomers, the spatial arrangement plays a crucial role in defining their identity and reactivity, making it an important concept in organic chemistry.