Alkanes Skeletal isomerization occurs in the
cracking process, used in the
petrochemical industry to convert straight chain
alkanes to
isoparaffins as exemplified in the conversion of
normal octane to
2,5-dimethylhexane (an "isoparaffin"): : Fuels containing branched
hydrocarbons are favored for internal combustion engines for their higher
octane rating. Diesel engines however operate better with straight-chain hydrocarbons.
Alkenes Cis vs trans Trans-
alkenes are about 1 kcal/mol more stable than cis-alkenes. An example of this effect is cis- vs trans-2-butene. The difference is attributed to unfavorable non-bonded interactions in the cis isomer. This effects helps to explain the formation of trans-fats in food processing. In some cases, the isomerization can be reversed using UV-light. The
trans isomer of
resveratrol converts to the
cis isomer in a
photochemical reaction. :
Terminal vs internal Terminal alkenes prefer to isomerize to internal alkenes: : The conversion essentially does not occur in the absence of metal catalysts. This process is employed in the
Shell higher olefin process to convert alpha-olefins to internal olefins, which are subjected to
olefin metathesis.
Other organic examples Isomerism is a major topic in sugar chemistry.
Glucose, the most common sugar, exists in four forms.
Aldose-ketose isomerism, also known as Lobry de Bruyn–van Ekenstein transformation, provides an example in
saccharide chemistry. :
Inorganic and organometallic chemistry : The compound with the formula Cyclopentadienyliron dicarbonyl dimer| exists as three isomers in solution. In one isomer the CO ligands are terminal. When a pair of CO are
bridging, cis and trans isomers are possible depending on the location of the
C5H5 groups. Another example in
organometallic chemistry is the
linkage isomerization of decaphenylferrocene, {{chem2|[(\h{5}C5
Ph5)2Fe]}}.
Biochemistry isomerases are a general class of
enzymes that convert a molecule from one
isomer to another. == Kinetic classification ==