Isopentane, also called methylbutane or 2-methylbutane, is a branched-chain saturated

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and Hydrophobe, hydrophobic; their odor is usually fain ...

(an alkane) with five

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, with formula or . Isopentane is a volatile and flammable liquid. It is one of three

structural isomers In chemistry, a structural isomer (or constitutional isomer in the IUPAC nomenclature) of a chemical compound, compound is a compound that contains the same number and type of atoms, but with a different connectivity (i.e. arrangement of chemica ...

with the molecular formula C₅H₁₂, the others being

pentane Pentane is an organic compound with the chemical formula, formula C5H12—that is, an alkane with five carbon atoms. The term may refer to any of three structural isomerism, structural isomers, or to a mixture of them: in the IUPAC nomenclature, h ...

(''n''-pentane) and

neopentane Neopentane, also called 2,2-dimethylpropane, is a double-branched-chain alkane with five carbon atoms. Neopentane is a flammable gas at room temperature and pressure which can condense into a highly volatile liquid on a cold day, in an ice bat ...

(2,2-dimethylpropane). Isopentane is commonly used in conjunction with

liquid nitrogen Liquid nitrogen (LN2) is nitrogen in a liquid state at cryogenics, low temperature. Liquid nitrogen has a boiling point of about . It is produced industrially by fractional distillation of liquid air. It is a colorless, mobile liquid whose vis ...

to achieve a liquid bath temperature of −160 °C.

Natural gas Natural gas (also fossil gas, methane gas, and gas) is a naturally occurring compound of gaseous hydrocarbons, primarily methane (95%), small amounts of higher alkanes, and traces of carbon dioxide and nitrogen, hydrogen sulfide and helium ...

typically contains 1% or less isopentane, but it is a significant component of natural gasoline.Ivan F. Avery, L. V. Harvey (1958):
Natural-gasoline and Cycling Plants in the United States
', Information circular, U.S. Department of the Interior, Bureau of Mines. 12 pages.

History

Although the mixture of pentanes was first isolated from the destructive distillation (

pyrolysis Pyrolysis is a process involving the Bond cleavage, separation of covalent bonds in organic matter by thermal decomposition within an Chemically inert, inert environment without oxygen. Etymology The word ''pyrolysis'' is coined from the Gree ...

) products of the boghead coal by Charles Greville Williams in 1862. In 1864–1865 two chemists tried to extract same hydrocarbons from the Pennsylvanian oil. Carl Schorlemmer noted "that a mere trace of the liquid boiled below 30°C", but the first to properly separate isomers (and thus discover isopentane) was American chemist Cyrus Warren (1824–1891) slightly later, who measured the boiling point of the more volatile one at 30°C.

Nomenclature

The traditional name isopentane, attested in English as early as 1875, was still retained in the 1993

IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...

recommendations, but is no longer recommended according to the 2013 recommendations. The preferred IUPAC name is the systematic name 2-methylbutane. An isopentyl group is a subset of the generic pentyl group. It has the chemical structure -CH₃CH₂CH(CH₃)₂.

Uses

Isopentane is used in a closed loop in geothermal power production to drive turbines. Isopentane is used, in conjunction with

dry ice Dry ice is the solid form of carbon dioxide. It is commonly used for temporary refrigeration as CO2 does not have a liquid state at normal atmospheric pressure and Sublimation (phase transition), sublimes directly from the solid state to the gas ...

or liquid nitrogen, to freeze tissues for cryosectioning in

histology Histology, also known as microscopic anatomy or microanatomy, is the branch of biology that studies the microscopic anatomy of biological tissue (biology), tissues. Histology is the microscopic counterpart to gross anatomy, which looks at large ...

. Isopentane is a major component (sometimes 30% or more) of natural gasoline, an analog of common

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 ...

-derived

gasoline Gasoline ( North American English) or petrol ( Commonwealth English) is a petrochemical product characterized as a transparent, yellowish, and flammable liquid normally used as a fuel for spark-ignited internal combustion engines. When for ...

that is condensed from natural gas. Its share in commercial car fuel is highly variable: 19–45% in 1990s Sweden, 4–31% in 1990s US and 3.6–11% in the US in 2011. It has a substantially higher

octane rating An octane rating, or octane number, is a standard measure of a liquid fuel, fuel's ability to withstand Compression ratio, compression in an internal combustion engine without causing engine knocking. The higher the octane number, the more compres ...

(RON 93.7) than ''n''-pentane (61.7), and therefore there is interest in conversion from the latter.Sheng Wang, Ying Zhang, Mao-Gang He, Xiong Zheng, and Li-Bin Chen (2014): "Thermal Diffusivity and Speed of Sound of Saturated Pentane from Light Scattering". ''International Journal of Thermophysics'', volume 35, pages 1450–1464.

References

External links

International Chemical Safety Card 1153IUPAC Nomenclature of Organic Chemistry
(online version of the "''Blue Book''") {{Authority control Alkanes