Isomeriat

Isomeriat, sometimes used as a translation of isomerization in some languages, refers to a chemical process in which a substance is converted into an isomer—an entity with the same molecular formula but a different arrangement of atoms. The term is used to denote rearrangements of connectivity or stereochemistry, and to distinguish these changes from reactions that alter the formula.

There are two broad classes: structural (constitutional) isomerization, where the connectivity of atoms changes; and stereoisomerization, where the arrangement in space changes without altering connectivity, including cis–trans (geometric) isomerization and enantiomerization. Rings can also open or close during an isomerization, yielding different ring sizes or fusion patterns.

Mechanisms vary: they may be catalyzed by acids or bases, or initiated thermally or by light. They can proceed via ionic, radical, or pericyclic pathways. Common motifs include [1,2]- or [1,3]-shifts, allylic rearrangements, and various sigmatropic rearrangements; E/Z isomerization around double bonds is a routine example in chemistry and biology.

Industrial and practical relevance: isomerization plays a key role in refining and petrochemistry, where straight-chain alkanes are converted to branched isomers to improve octane ratings. Alkenes can be isomerized to reach more reactive or selective configurations. In synthesis, controlled isomerization is used to set or adjust stereochemistry, to access different building blocks, and to alter physical properties of materials or fuels.

See also: isomer, structural isomer, stereochemistry, catalysis, sigmatropic rearrangement.