Pentenes are

alkene In organic chemistry, an alkene, or olefin, is a hydrocarbon containing a carbon–carbon double bond. The double bond may be internal or at the terminal position. Terminal alkenes are also known as Alpha-olefin, α-olefins. The Internationa ...

s 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 In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist betw ...

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

has a ''cis'' or ''trans'' form.

Straight-chain isomers

1-Pentene is an

alpha-olefin In organic chemistry, terminal alkenes (alpha-olefins, α-olefins, or 1-alkenes) are a family of organic compounds which are alkenes (also known as olefins) with a chemical formula , distinguished by having a double bond at the primary, Alpha an ...

. 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 Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon–carbon bond, carbon–carbon doub ...

and

propylene Propylene, also known as propene, is an unsaturated organic compound with the chemical formula . It has one double bond, and is the second simplest member of the alkene class of hydrocarbons. It is a colorless gas with a faint petroleum-like o ...

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 Fluid catalytic cracking (FCC) is the conversion process used in petroleum refineries to convert the high-boiling point, high-molecular weight hydrocarbon fractions of petroleum (crude oils) into gasoline, alkene gases, and other petroleum produc ...

(FCC). The DCC uses vacuum gas oil (VGO) as a feedstock to produce primarily

isobutylene Isobutylene (or 2-methylpropene) is a hydrocarbon with the chemical formula . It is a four-carbon branched alkene (olefin), one of the four isomers of butylene. It is a colorless flammable gas, and is of considerable industrial value. Product ...

, 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 unit An alkylation unit (alky) is one of the conversion processes used in petroleum refineries. It is used to convert isobutane and low-molecular-weight alkenes (primarily a mixture of propene and butene) into alkylate, a high octane gasoline compo ...

s 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