Geometrical isomers are molecules that have the same molecular formula and connectivity but differ in the spatial arrangement of their atoms. This results in different physical and chemical properties.
Geometrical isomers form due to the presence of a double bond or a ring in a molecule, which restricts the rotation of atoms around the bond. This leads to different possible arrangements of the atoms.
Geometrical isomers can be identified by their different physical properties, such as boiling point, melting point, and solubility. They may also exhibit different chemical reactivity and can be distinguished by analytical techniques like NMR and IR spectroscopy.
Cis isomers have the same groups on the same side of a double bond or ring, while trans isomers have the same groups on opposite sides. This results in different shapes and properties of the molecules.
Some common examples of geometrical isomers include cis- and trans-2-butene, cis- and trans-1,2-dichloroethene, and cis- and trans-1,2-dimethylcyclohexane.