Geometric isomerism

Geometric isomerism is stereoisomerism in which restricted rotation creates distinct spatial arrangements of groups, commonly around double bonds or within rings. These arrangements can have different physical or chemical properties.

Stereoisomerism: Stereoisomerism occurs when molecules have the same connectivity but differ in the three-dimensional arrangement of their atoms. Geometric isomerism is one type of stereoisomerism.
Pi bond: A pi bond is a covalent bond formed by sideways overlap of parallel orbitals, with electron density above and below the internuclear axis. Rotating an alkene would disrupt the pi bond and requires substantial energy.
Maleic acid: Maleic acid is the cis isomer of butenedioic acid, with both carboxyl groups on the same side of its carbon–carbon double bond. Its geometry enables intramolecular dehydration to form maleic anhydride.
Optical isomerism: Optical isomerism is stereoisomerism associated with chiral molecules that rotate plane-polarized light differently. Geometric isomers arise from restricted rotation, not necessarily molecular chirality.
Cis–trans isomerism: Cis–trans isomerism distinguishes arrangements by whether specified groups lie on the same or opposite sides of a reference feature. This is the common naming system for simple geometric isomers.
Rotation barrier: A rotation barrier is the energy required to rotate one part of a molecule relative to another. The high barrier about a double bond keeps its geometric arrangements distinct.
Fumaric acid: Fumaric acid is the trans isomer of butenedioic acid, with its carboxyl groups on opposite sides of the double bond. Its trans arrangement gives it properties distinct from cis maleic acid.
Enantiomer: Enantiomers are stereoisomers that are non-superimposable mirror images of one another. Many geometric isomer pairs are not mirror-image pairs.
E–Z notation: E–Z notation names alkene configurations by comparing the priorities of substituents on each carbon. It names double-bond configurations even when cis–trans labels are ambiguous.
Cycloalkane: A cycloalkane is a saturated hydrocarbon whose carbon atoms form one or more rings. A ring can prevent substituents from exchanging positions by free rotation.

Linked from 16 pages