What is isomerism in organic chemistry?

Isomerism in organic chemistry refers to the phenomenon where compounds have the same molecular formula but differ in the arrangement of their atoms, leading to distinct structural or spatial characteristics. This means that even though two compounds contain exactly the same number of each type of atom (for instance, the same number of carbon, hydrogen, and other elements), how those atoms are connected or arranged can differ significantly.

This is crucial in organic chemistry because these differences in structure can result in different physical and chemical properties, affecting reactivity, boiling points, and biological activity. For example, butane and isobutane have the same molecular formula (C4H10) but exist as different structures, leading to different physical properties and uses.

In contrast, compounds with different molecular formulas do not represent isomerism, as they are entirely different substances. Transformed compounds refer to chemical reactions rather than structural differences, and compounds that exist in multiple physical states fall under physical properties rather than the concept of isomerism itself. Understanding isomerism is fundamental in organic chemistry, particularly when dealing with complex molecules and reactions.