Pentenes are
alkenes with the
chemical formula
A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...
. Each molecule contains one
double bond within its molecular structure. Six different compounds are in this class, differing from each other by whether the
carbon
Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...
atoms are attached linearly or in a branched structure and whether the
double bond has a
''cis'' or ''trans'' form.
Straight-chain isomers
1-Pentene is an
alpha-olefin. Most often, 1-pentene is made as a byproduct of
catalytic
Catalysis () is the increase in reaction rate, rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst ...
or
thermal cracking of
petroleum
Petroleum, also known as crude oil or simply oil, is a naturally occurring, yellowish-black liquid chemical mixture found in geological formations, consisting mainly of hydrocarbons. The term ''petroleum'' refers both to naturally occurring un ...
or during the production of
ethylene and
propylene via thermal cracking of hydrocarbon fractions.
As of 2010s, the only commercial manufacturer of 1-pentene was
Sasol Ltd., where it is separated from crude by the
Fischer-Tropsch process.
2-Pentene has two geometric isomers: ''cis''-2-pentene and ''trans''-2-pentene. ''Cis''-2-Pentene is used in
olefin metathesis.
Branched-chain isomers
The branched isomers are 2-methylbut-1-ene, 3-methylbut-1-ene (isopentene), and
2-methylbut-2-ene (isoamylene).
Isoamylene is one of the three main byproducts of
deep catalytic cracking (DCC), which is very similar to the operation of
fluid catalytic cracking (FCC). The DCC uses
vacuum gas oil (VGO) as a feedstock to produce primarily
propylene,
isobutylene, and isoamylene. The rise in demand for
polypropylene
Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications. It is produced via chain-growth polymerization from the monomer Propene, propylene.
Polypropylene belongs to the group of polyolefin ...
has encouraged the growth of the DCC, which is operated very much like the FCC. Isobutylene and isoamylene feedstocks are necessary for the production of the much debated gasoline blending components
methyl ''tert''-butyl ether and
''tert''-amyl methyl ether.
Production of fuels
Propylene, isobutene, and amylenes are feedstocks in the
alkylation units of refineries. Using isobutane, blendstocks are generated with high branching for good combustion characteristics. Amylenes are valued as precursors to fuels, especially aviation fuels of relatively low volatility, as required by various regulations.
References
{{Hydrides by group
Alkenes