Editing Isomerization (section)

== Kinetic classification ==
From the [[Chemical kinetics|kinetic viewpoint]], isomerizations can be classified into two categories.<ref>{{Cite book |last=Arnaut |first=Luís G. |url=https://www.worldcat.org/title/on1063653763 |title=Chemical kinetics: from molecular structure to chemical reactivity |date=2021 |publisher=Elsevier |isbn=978-0-444-64039-0 |edition=Second |location=Amsterdam, Netherlands ; Cambridge, MA |oclc=on1063653763}}</ref> Cases in the first category involve transformations between equivalent structures. Most chemical species are in principle susceptible to such processes. Many such cases involve [[Fluxional molecule|fluxional molecules]], such as the [[Cyclohexane conformation|cyclohexane ring flip]] (chair inversion), the [[pyramidal inversion]] of ammonia, the [[Berry mechanism|Berry pseudorotation]] in pentacoordinate compounds (e.g. PF<sub>5</sub>, Fe(CO)<sub>5</sub>), the [[Bullvalene|Cope rearrangements of bullvalene]] or the [[Ray–Dutt twist|Ray-Dutt]]/[[Bailar twist|Bailar twists]] for the racemization of octahedral complexes with three bidentate chelate rings ([[Axial chirality|helical chirality]]). 

In the second broad category of isomerizations, the isomers are nonequivalent. Examples include [[Tautomer|tautomerizations]] ([[Enol|keto-enol]], [[Lactam|lactam-lactim]], [[Imidic acid|amide-imidic]], [[Enamine|enamine-imine]], [[Nitroso|nitroso-oxime]], [[Ketene|ketene-ynol]], etc) in which one isomer is more stable than the other.
[[File:Concentration_profile_for_the_scheme_A_=_B_when_k1_=_k2.png|thumb|Concentration profile for the reaction mechanism A = B when k1 = k2]]
This scheme leads to the following system of differential [[Rate equation|rate equations]]: