isomerisaation

Isomerisaation (isomerisation) refers to the transformation of a molecule into another species that has the same molecular formula but a different arrangement of atoms. The term covers several distinct phenomena in chemistry, unified by the idea that the product is an isomer of the starting material. Inorganic and organic contexts both use the concept, with differing implications.

Isomerization is commonly divided into structural (constitutional) isomerization, where the connectivity of atoms changes, and stereoisomerization, where connectivity remains but spatial arrangement changes. Structural isomers include straight-chain versus branched alkanes (for example, n-butane C4H10 and isobutane C4H10). Stereoisomerization includes geometric isomers such as cis- and trans- forms around a double bond, enantiomers that are non-superimposable mirror images, and diastereomers.

Mechanistically, isomerizations occur via thermal rearrangements, acid- or base-catalyzed processes, photochemical steps, or metal- or radical-catalyzed pathways. Classic examples are photoisomerization of stilbene (trans-stilbene to cis-stilbene) and keto-enol tautomerism in carbonyl compounds. In industry, hydrocarbon isomerization converts straight-chain alkanes to branched isomers to improve octane rating, often using noble metal catalysts. Biologically, isomerases are enzymes that catalyze specific isomerizations in metabolism, such as racemases and cis-trans isomerases, enabling rearrangements within biomolecules without changing composition.

Isomerization is a fundamental concept in synthesis, catalysis, and materials science, shaping properties such as boiling points, reactivity, and stereochemistry. The study of isomerisation bridges organic, inorganic, physical, and biological chemistry.