What is 'isomerism' in organic chemistry?

Isomerism in organic chemistry refers to the phenomenon where two or more compounds share the same molecular formula but exhibit differences in their structural arrangement or connectivity of atoms. This distinction leads to variations in their chemical and physical properties. For instance, compounds that are isomers can differ in how their atoms are bonded to one another, resulting in different structural formations, such as straight-chain versus branched hydrocarbons, or in the arrangement around a double bond, leading to geometric isomers.

Isomerism can also encompass stereoisomerism, where atoms are connected in the same order but differ in their spatial orientation, such as in cis-trans or enantiomers. This concept is fundamental to understanding diversity in organic compounds, as the same atoms can lead to a variety of structures with distinct characteristics. This intrinsic variability is crucial in organic chemistry, particularly when analyzing reaction mechanisms, predicting reactivity, or evaluating compound behaviors in biological systems.