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N-Substituted isoindoles do not engage is tautomerism and are therefore simpler to study.
File:PY139.svg,
organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clayden, J.; ...
and heterocyclic chemistry
A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). Heterocyclic chemistry is the branch of organic chemistry dealing with the synthesis, properties, and ...
, isoindole consists of a benzene
Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms, ...
ring fused with pyrrole. The compound is an isomer
In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers.
Iso ...
of indole
Indole is an aromatic heterocyclic organic compound
In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other c ...
. Its reduced form is isoindoline
Isoindoline is a heterocyclic organic compound with the molecular formula C8H9N. The parent compound has a bicyclic structure, consisting of a six-membered benzene ring fused to a five-membered nitrogen-containing ring. The compound's structure is ...
. The parent isoindole is a rarely encountered in the technical literature, but substituted derivatives are useful commercially and occur naturally. Isoindoles units occur in phthalocyanine
Phthalocyanine () is a large, aromatic, macrocyclic, organic compound with the formula and is of theoretical or specialized interest in chemical dyes and photoelectricity.
It is composed of four isoindole units linked by a ring of nitrogen atom ...
s, an important family of dyes. Some alkaloid
Alkaloids are a class of basic, naturally occurring organic compounds that contain at least one nitrogen atom. This group also includes some related compounds with neutral and even weakly acidic properties. Some synthetic compounds of similar ...
s containing isoindole have been isolated and characterized.Heugebaert, Thomas S. A.; Roman, Bart I.; Stevens, Christian V. "Synthesis of isoindoles and related iso-condensed heteroaromatic pyrroles" Chemical Society Reviews 2012, volume 41, pp. 5626-5640.
Synthesis
The parent isoindole was prepared byflash vacuum pyrolysis Flash vacuum pyrolysis (FVP) is a technique in organic synthesis. It entails heating a precursor molecule intensely and briefly. Two key parameters are the temperature and duration (or residence time), which are adjusted to optimize yield, conver ...
of an N-substituted isoindoline. N-Substituted isoindoles, which are easier to handle, can be prepared by dehydration of isoindoline-N-oxides. They also arise by myriad other methods, e.g., starting from xylylene dibromide (C6H4(CH2Br)2).
Structure and tautomerism of 2-H-isoindoles
Unlike indole, isoindoles exhibit noticeable alternation in the C-C bond lengths, which is consistent with their description as pyrrole derivatives fused to a butadiene. In solution, the 2''H''-isoindoletautomer
Tautomers () are structural isomers (constitutional isomers) of chemical compounds that readily interconvert.
The chemical reaction interconverting the two is called tautomerization. This conversion commonly results from the relocation of a hyd ...
predominates. It resembles a pyrrole more than a simple imine
In organic chemistry, an imine ( or ) is a functional group or organic compound containing a carbon–nitrogen double bond (). The nitrogen atom can be attached to a hydrogen or an organic group (R). The carbon atom has two additional single bo ...
. The degree to which the 2''H'' predominates depends on the solvent, and can vary with the substituent in substituted isoindoles.
:
N-Substituted isoindoles do not engage is tautomerism and are therefore simpler to study.
Isoindole-1,3-diones and related derivatives
The commercially importantphthalimide
Phthalimide is the organic compound with the formula C6H4(CO)2NH. It is the imide derivative of phthalic anhydride. It is a sublimable white solid that is slightly soluble in water but more so upon addition of base. It is used as a precursor ...
is an ''isoindole-1,3-dione'' with two carbonyl
In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups. A compound containing a ...
groups attached to the heterocyclic ring.
Pigment yellow 139
Pigment yellow 139 is an organic compound that is used as a yellow-orange pigment. It is classified as a derivative of isoindoline. This yellow-orange solid is virtually insoluble in most solvents.K. Hunger. W. Herbst "Pigments, Organic" in ''Ull ...
, a common high performance pigment.
File:PY185.svg, Pigment yellow 185
Pigment yellow 185 is an organic compound that is used as a green yellow pigment and optical brightener. It is classified as a derivative of isoindoline. This yellow green compound is prepared by addition of ammonia to ''o''- phthalonitrile to ...
, a common high performance pigment.
File:Copper phthalocyanine.svg, Copper phthalocyanine
Copper phthalocyanine (CuPc), also called phthalocyanine blue, phthalo blue and many other names, is a bright, crystalline, synthetic blue pigment from the group of phthalocyanine dyes. Its brilliant blue is frequently used in paints and dy ...
, one of the most pervasive synthetic pigments.
See also
* 1,3-Disubstituted Isoindolines. *Isoindene
Isoindene is a flammable polycyclic hydrocarbon with chemical formula C9H8. It is composed of a cyclohexadiene ring fused with a cyclopentadiene ring.
See also
* Indene
* Isoindole
In organic chemistry and heterocyclic chemistry, isoindole ...
with nitrogen replaced by a methylene group
In organic chemistry, a methylene group is any part of a molecule that consists of two hydrogen atoms bound to a carbon atom, which is connected to the remainder of the molecule by two single bonds. The group may be represented as , where the '< ...
.
References
{{Simple aromatic rings Simple aromatic rings