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Structural isomerism
 
 
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Structural isomerism, or constitutional isomerism, is a form of isomerism
Isomer

In chemistry, isomers are compounds with the same molecular formula but different structural formulae. Isomers do not necessarily share similar properties unless they also have the same functional groups....
 in which molecule
Molecule

In chemistry, a molecule is defined as a sufficiently stable, electric charge neutral group of at least two atoms in a definite arrangement held together by very strong chemical bonds....
s with the same molecular formula have atom
Atom

|-! bgcolor=gray | Properties|-||}The atom is a basic unit of matter consisting of a dense, central atomic nucleus surrounded by a electron cloud of electric charge electrons....
s bonded together in different orders, as opposed to stereoisomerism
Stereoisomerism

Stereoisomers are isomer that have the same molecular formula and sequence of bonded atoms , but which differ in the three dimensional orientations of their atoms in space....
.

Three categories of constitutional isomers are skeletal, positional, and functional isomers.

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Example of skeletal isomerism
n-pentane
Pentane

Pentane is any or one of the organic compounds with the chemical formula C5H12. This alkane is a component of some fuels and is employed as a specialty solvent in the laboratory....
 Isopentane
Isopentane

Isopentane, carbonhydrogen, also called methylbutane or 2-methylbutane, is a branched-chain alkane with five carbon atoms. Isopentane is an extremely Volatility and extremely flammable liquid at room temperature and pressure....
In skeletal isomerism, or chain isomerism, components of the (usually carbon) skeleton are distinctly re-ordered to create different structures.






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Encyclopedia


Structural isomerism, or constitutional isomerism, is a form of isomerism
Isomer

In chemistry, isomers are compounds with the same molecular formula but different structural formulae. Isomers do not necessarily share similar properties unless they also have the same functional groups....
 in which molecule
Molecule

In chemistry, a molecule is defined as a sufficiently stable, electric charge neutral group of at least two atoms in a definite arrangement held together by very strong chemical bonds....
s with the same molecular formula have atom
Atom

|-! bgcolor=gray | Properties|-||}The atom is a basic unit of matter consisting of a dense, central atomic nucleus surrounded by a electron cloud of electric charge electrons....
s bonded together in different orders, as opposed to stereoisomerism
Stereoisomerism

Stereoisomers are isomer that have the same molecular formula and sequence of bonded atoms , but which differ in the three dimensional orientations of their atoms in space....
.

Three categories of constitutional isomers are skeletal, positional, and functional isomers.

Skeletal isomerism

Example of skeletal isomerism
n-pentane
Pentane

Pentane is any or one of the organic compounds with the chemical formula C5H12. This alkane is a component of some fuels and is employed as a specialty solvent in the laboratory....
 Isopentane
Isopentane

Isopentane, carbonhydrogen, also called methylbutane or 2-methylbutane, is a branched-chain alkane with five carbon atoms. Isopentane is an extremely Volatility and extremely flammable liquid at room temperature and pressure....
In skeletal isomerism, or chain isomerism, components of the (usually carbon) skeleton are distinctly re-ordered to create different structures. For example 3-methylpentane
3-Methylpentane

3-Methylpentane is a branching alkane with the molecular formula C6H14. It is a structural isomer of hexane composed of a methyl group bonded to the third carbon atom in a pentane chain....
 is a chain isomer of 2-methylpentane. Pentane
Pentane

Pentane is any or one of the organic compounds with the chemical formula C5H12. This alkane is a component of some fuels and is employed as a specialty solvent in the laboratory....
 exists as three isomers: n-pentane, isopentane
Isopentane

Isopentane, carbonhydrogen, also called methylbutane or 2-methylbutane, is a branched-chain alkane with five carbon atoms. Isopentane is an extremely Volatility and extremely flammable liquid at room temperature and pressure....
 and neopentane
Neopentane

Neopentane, also called dimethylpropane or 2,2-dimethylpropane, is a double-branched-chain alkane with five carbon atoms. Neopentane is an extremely flammable gas at room temperature and pressure which can condense into a highly Volatility liquid on a cold day, in an ice bath, or when compressed to a higher pressure....
. The number of skeletal isomers of an n-carbon alkane
Alkane

Alkanes, also known as paraffins, are chemical compounds that consist only of the elements carbon and hydrogen , wherein these atoms are linked together exclusively by single bonds without any cyclic structure ....
 is documented at .



Position isomerism

Position Isomer
In position isomerism a functional group
Functional group

In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules....
 changes position on the chain. In the diagram, pentan-2-ol has become pentan-3-ol. Many aromatic isomers exist because substituents can be positioned on different parts of the benzene ring. Only one isomer of phenol
Phenol

Phenol, also known as carbolic acid, is a toxic, white crystalline solid with a sweet tarry odor, commonly referred to as a "hospital smell"....
 or hydroxybenzene exists but cresol
Cresol

Cresols are organic compounds which are methyl groupphenols. They are a widely occurring natural and manufactured group of aromatic organic compounds which are categorized as phenols ....
 or methylphenol has three isomers where the additional methyl group can be placed on three different positions on the ring. Xylenol
Xylenol

Xylenol or dimethylphenol is an arene compound with two methyl groups and a hydroxyl group. 6 isomers exist of xylenol of which 2,6-xylenol with both methyl group in an arene substitution patterns with respect to the hydroxyl group is the most important....
 has one hydroxyl group and two methyl groups and a total of 6 isomers exist.



Functional group isomerism

In functional group isomerism a functional group splits up and becomes a different group. Here is an example of functional group isomerism: take cyclohexane
Cyclohexane

Cyclohexane is a cycloalkane with the molecular formula Carbon6Hydrogen12. Cyclohexane is used as a nonpolar solvent for the chemical industry, and also as a raw material for the industrial production of adipic acid and caprolactam, both of which are intermediates used in the production of nylon....
, C6H12 and hex-1-ene, also C6H12. These two are considered functional group isomers because cyclohexane is an alkane
Alkane

Alkanes, also known as paraffins, are chemical compounds that consist only of the elements carbon and hydrogen , wherein these atoms are linked together exclusively by single bonds without any cyclic structure ....
 and hex-1-ene is an alkene
Alkene

In organic chemistry, an alkene, olefin, or olefine is an Saturation chemical compound containing at least one carbon-to-carbon double bond....
. Both must have the same molecular formula.

Metamerism

This type of isomerism is due to the unequal distribution of carbon atoms on either side of functional group. Metamerism belongs to same [homologous series]. Example: DIETHYL ETHERCH3-CH2-O-CH2-CH3 METHYL PROPYLETHER CH3-O-C3H7


See also

  • Isomer
    Isomer

    In chemistry, isomers are compounds with the same molecular formula but different structural formulae. Isomers do not necessarily share similar properties unless they also have the same functional groups....
  • Cis-trans isomerism
  • Chirality (chemistry)
    Chirality (chemistry)

    The term chiral is used to describe an object that is non-Superposition on its mirror image.Human hands are perhaps the most universally recognized example of chirality: The left hand is a non-superposable mirror image of the right hand; no matter how the two hands are oriented, it is impossible for all the major features of both hands...
  • Tautomer
    Tautomer

    Tautomers are isomers of organic compounds that readily interconvert by a chemical reaction called tautomerization. Commonly this reaction results in the formal migration of a hydrogen atom or proton, accompanied by a switch of a single bond and adjacent double bond....