Isomer

Alanine has two isomers. They are exactly the same except they are backwards from each other. This sort of isomer is called an optical isomer

An isomer in chemistry is a chemical compound that has the same molecular formula as another, but it has a different arrangement of atoms in space. In other words, isomers are compounds with the same molecular formula but different structural formula. Different isomers have different chemical properties (that is, they may look, or smell, or taste different from each other).^[1]^[2]

There are two main categories: stereoisomers and structural isomers. Structural isomers are isomers with the atoms making up the molecule joined together in different ways. Structural isomers can be classified further as chain isomers, position isomers, function group isomers, tautomers metamers and ring chain isomers.^[3]

Stereoisomers have different positions of atoms in space and are much more subtle than structural isomers. See enantiomer for stereoisomers that are related to each other by a reflection: they are mirror images of each other that are non-superimposable.

Isomer Media

SVG version of
Isomerism.png, made using
Cis-2-butene.svg and
Trans-2-butene.svg by User:JaGa and
Conformers.svg by
Structural isomers of C₃H₈O: I 1-propanol, II 2-propanol, III ethyl-methyl-ether.
Propadiene is the organic compound with the formula H2C=C=CH2. It is the simplest allene, a compound with conjoined C=C double bonds. As a constituent of MAPP gas, it was used as a fuel for specialized welding.
PropyneDflat
chemical structure of w:Cyclopropene
Hypothetical structural diagram of orho-xylene (1,2-methylbenzene) with a cyclohexatriene core, with a SINGLE bond between the methylated carbons (1 and 2). One of the two forms used in the "resonance" model of the molecule, an approximation of the pi bonding delocalized over the whole ring. See
O xylene B.png.*Created with the GNU/Linux Gimp image editor, based on
O xylène.png.
Hypothetical structural diagram of orho-xylene (1,2-methylbenzene) with a cyclohexatriene core, with a DOUBLE bond between the methylated carbons (1 and 2). One of the two forms used in the "resonance" model of the molecule, an approximation of the pi bonding delocalized over the whole ring. See
O xylene A.png.*Created with the GNU/Linux Gimp image editor, based on
O xylène.png.
Molecular models of cyclohexane in boat and chair conformations. The carbon atoms are colored amber or blue according to whether they lie above or below the mean plane of the ring. The C–C bonds on the ring are light green.
The two isomeric complexes, cisplatin and transplatin, are examples of square planar MX2Y2 molecules with M = Pt.
Formation of decaphenylferrocene from its linkage isomer