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In chemistry, isomers are molecules or polyatomic ions with identical molecular formula – that is, the same number of atoms of each element – but distinct arrangements of atoms in space. [1] Isomerism refers to the existence or possibility of isomers. Isomers do not necessarily share similar chemical or physical properties.
In chemistry, isomerization or isomerisation is the process in which a molecule, polyatomic ion or molecular fragment is transformed into an isomer with a different chemical structure. [1] Enolization is an example of isomerization, as is tautomerization. [2] When the isomerization occurs intramolecularly it may be called a rearrangement reaction.
The isomerization energy, for example, for converting from a stable cis isomer to the less stable trans isomer is greater than for the reverse reaction, explaining why in the absence of isomerases or an outside energy source such as ultraviolet radiation a given cis isomer tends to be present in greater amounts than the trans isomer.
In enzymology, a xylose isomerase (EC 5.3.1.5) is an enzyme that catalyzes the interconversion of D-xylose and D-xylulose.This enzyme belongs to the family of isomerases, specifically those intramolecular oxidoreductases interconverting aldoses and ketoses.
These include meso compounds, cis–trans isomers, E-Z isomers, and non-enantiomeric optical isomers. Diastereomers seldom have the same physical properties. In the example shown below, the meso form of tartaric acid forms a diastereomeric pair with both levo- and dextro-tartaric acids, which form an enantiomeric pair.
Isotopomers or isotopic isomers are isomers which differ by isotopic substitution, and which have the same number of atoms of each isotope but in a different arrangement. For example, CH 3 OD and CH 2 DOH are two isotopomers of monodeuterated methanol .
In the red linkage isomer, the nitrito is bound through one oxygen atom. The O-bonded isomer is often written as [Co(NH 3) 5 (ONO)] 2+. Although the existence of the isomers had been known since the late 1800s, only in 1907 was the difference explained. [2] It was later shown that the red isomer converted to the yellow isomer upon UV-irradiation.
Isocitric acid is commonly used as a marker to detect the authenticity and quality of fruit products, most often citrus juices. In authentic orange juice, for example, the ratio of citric acid to D-isocitric acid is usually less than 130. An isocitric acid value higher than this may be indicative of fruit juice adulteration.