transisómerism

Transisomerism is a type of stereoisomerism that occurs in molecules where there is restricted rotation around a bond, typically a double bond or a ring. This restricted rotation leads to the existence of two or more distinct spatial arrangements of atoms or groups around the central bond. These different arrangements are called isomers.

For a molecule to exhibit transisomerism, there must be two different groups attached to each of the atoms involved in the restricted rotation. For example, in alkenes, if each carbon atom of the double bond is bonded to two different groups, then cis-trans isomerism is possible. The cis isomer has similar groups on the same side of the double bond, while the trans isomer has similar groups on opposite sides.

In the case of cyclic compounds, transisomerism arises from the relative positions of substituents on the ring. If two substituents are on opposite sides of the plane of the ring, they are in a trans configuration. If they are on the same side, they are in a cis configuration.

Transisomers have different physical properties, such as melting point, boiling point, and solubility, as well as different chemical reactivity. They are also often perceived differently by biological systems, which can lead to variations in their biological activity. The terminology "cis" and "trans" is widely used, but for more complex cases with more than two different substituents, the E/Z nomenclature is employed.