Transisomerism

Transisomerism is a type of stereoisomerism that occurs in molecules where atoms or groups of atoms are arranged on opposite sides of a plane. This phenomenon is most commonly observed in alkenes and cyclic compounds. In alkenes, transisomerism arises from the restricted rotation around the carbon-carbon double bond. If the two identical substituents on each carbon of the double bond are on opposite sides, the isomer is designated as trans. If they are on the same side, it is designated as cis. This difference in spatial arrangement leads to distinct physical and chemical properties, such as melting point, boiling point, and reactivity.

In cyclic compounds, transisomerism refers to the relative positions of substituents attached to 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. Similar to alkenes, cis and trans isomers in cyclic systems exhibit different properties due to their distinct three-dimensional structures. For example, in cyclohexane derivatives, the trans isomer may have both substituents in equatorial positions, which is generally more stable than the cis isomer where one substituent might be axial. The presence of transisomerism is a crucial consideration in organic chemistry, influencing reaction pathways, molecular recognition, and the biological activity of many compounds.