Chemical compounds with the same molecular formula but different atomic arrangements
This article is about the chemical concept. For "isomerism" of atomic nuclei, see nuclear isomer. For part of the body of the proarticulates, see isomer (Proarticulata).
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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] Diamond and graphite are a familiar example; they are isomers of carbon. Isomerism refers to the existence or possibility of isomers.
Isomers do not necessarily share similar chemical or physical properties. Two main forms of isomerism are structural (or constitutional) isomerism, in which bonds between the atoms differ; and stereoisomerism or (spatial isomerism), in which the bonds are the same but the relative positions of the atoms differ.
Isomeric relationships form a hierarchy. Two chemicals might be the same constitutional isomer, but upon deeper analysis be stereoisomers of each other. Two molecules that are the same stereoisomer as each other might be in different conformational forms or be different isotopologues. The depth of analysis depends on the field of study or the chemical and physical properties of interest.
The English word "isomer" (/ˈaɪsəmər/) is a back-formation from "isomeric",[2] which was borrowed through German isomerisch[3] from Swedish isomerisk; which in turn was coined from Greek ἰσόμερoς isómeros, with roots isos = "equal", méros = "part".[4]
Types of isomers
^Petrucci, Ralph H.; Harwood, William S.; Herring, F. Geoffrey (2002). General chemistry: principles and modern applications (8th ed.). Upper Saddle River, N.J: Prentice Hall. p. 91]. ISBN 978-0-13-014329-7. LCCN 2001032331. OCLC 46872308.
^Merriam-Webster: "isomer" Archived 21 October 2020 at the Wayback Machine online dictionary entry. Accessed on 2020-08-26
^Merriam-Webster: "isomeric" Archived 26 October 2020 at the Wayback Machine online dictionary entry. Accessed on 2020-08-26
^Cite error: The named reference berz1830 was invoked but never defined (see the help page).
are a familiar example; they are isomers of carbon. Isomerism refers to the existence or possibility of isomers. Isomers do not necessarily share similar...
In chemistry, conformational isomerism is a form of stereoisomerism in which the isomers can be interconverted just by rotations about formally single...
A nuclear isomer is a metastable state of an atomic nucleus, in which one or more nucleons (protons or neutrons) occupy excited state (higher energy) levels...
In chemistry, linkage isomerism or ambidentate isomerism is a form of isomerism in which certain coordination compounds have the same composition but...
In coordination chemistry, ligand isomerism is a type of structural isomerism in coordination complexes which arises from the presence of ligands which...
Coordination isomerism is a form of structural isomerism in which the composition of the coordination complex ion varies. In a coordination isomer the total...
In stereochemistry, stereoisomerism, or spatial isomerism, is a form of isomerism in which molecules have the same molecular formula and sequence of bonded...
In chemistry, a structural isomer (or constitutional isomer in the IUPAC nomenclature) of a compound is another compound whose molecule has the same number...
simple disubstituted arenes, the three isomers tend to have rather similar boiling points. However, the para isomer usually has the highest melting point...
A meso compound or meso isomer is an optically inactive isomer in a set of stereoisomers, at least two of which are optically active. This means that despite...
coordination chemistry, hydration isomerism is a kind of isomerism that is observed in some solids. Hydration isomers have identical formula but differ...
isomerism, solvate or hydrate isomerism, linkage isomerism and coordination isomerism. Ionisation isomerism – the isomers give different ions in solution...
of gamma rays from excited nuclei, usually involving a specific nuclear isomer. It is analogous to conventional fluorescence, which is defined as the emission...
are valence isomers when they are constitutional isomers that can interconvert through pericyclic reactions. There are many valence isomers one can draw...
CH3(CH2)6CH3. Octane has many structural isomers that differ by the location of branching in the carbon chain. One of these isomers, 2,2,4-trimethylpentane (commonly...
called isomer shift) is the shift on atomic spectral lines and gamma spectral lines, which occurs as a consequence of replacement of one nuclear isomer by...
(enantíos) 'opposite', and μέρος (méros) 'part') – also called optical isomer, antipode, or optical antipode – is one of two stereoisomers that are nonsuperposable...
Topoisomers or topological isomers are molecules with the same chemical formula and stereochemical bond connectivities but different topologies. Examples...
as glucose, in solution. In fact one name for D-glucose (the biological isomer), is dextrose, referring to the fact that it causes linearly polarized light...
half-lives that are less than ten minutes. One isotope, 229Th, has a nuclear isomer (or metastable state) with a remarkably low excitation energy, recently...
(parahydrogen). These two forms are often referred to as spin isomers or as nuclear spin isomers. Parahydrogen is in a lower energy state than is orthohydrogen...
prohibited. Among the molecules which have the chemical formula C4H8 four isomers are alkenes. All four of these hydrocarbons have four carbon atoms and...
the major component in the volatile oil of citrus fruit peels. The (+)-isomer, occurring more commonly in nature as the fragrance of oranges, is a flavoring...
(IUPAC). IUPAC Nomenclature ensures that each compound (and its various isomers) have only one formally accepted name known as the systematic IUPAC name...
Three isomers are common, varying by the positions of the isocyanate groups around the rings: 2,2′-MDI, 2,4′-MDI, and 4,4′-MDI. The 4,4′ isomer is most...
This is the list of structural isomers of nonane. There are 35.[citation needed] Nonane 2-Methyloctane 3-Methyloctane 4-Methyloctane 2,2-Dimethylheptane...
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