Hexane
Overview
 
Hexane is a hydrocarbon
Hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....

 with the chemical formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 C6H14; that is, an alkane
Alkane
Alkanes are chemical compounds that consist only of hydrogen and carbon atoms and are bonded exclusively by single bonds without any cycles...

 with six carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

 atoms.

The term may refer to any of four other structural isomers with that formula, or to a mixture of them. In the IUPAC
International Union of Pure and Applied Chemistry
The International Union of Pure and Applied Chemistry is an international federation of National Adhering Organizations that represents chemists in individual countries. It is a member of the International Council for Science . The international headquarters of IUPAC is located in Zürich,...

 nomenclature, however, hexane is the unbranched isomer (n-hexane); the other four structures are named as methyl
Methyl group
Methyl group is a functional group derived from methane, containing one carbon atom bonded to three hydrogen atoms —CH3. The group is often abbreviated Me. Such hydrocarbon groups occur in many organic compounds. The methyl group can be found in three forms: anion, cation and radical. The anion...

ated derivatives of pentane and butane. IUPAC also uses the term as the root of many compounds with a linear six-carbon backbone, such as 2-methylhexane
2-Methylhexane
2-Methylhexane is an isomer of heptane. It is structurally a hexane molecule with a methyl group attached to its second carbon atom...

 C7H16, which is also called "isoheptane".

Hexanes are significant constituents of gasoline
Gasoline
Gasoline , or petrol , is a toxic, translucent, petroleum-derived liquid that is primarily used as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Some gasolines also contain...

.
Encyclopedia
Hexane is a hydrocarbon
Hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....

 with the chemical formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 C6H14; that is, an alkane
Alkane
Alkanes are chemical compounds that consist only of hydrogen and carbon atoms and are bonded exclusively by single bonds without any cycles...

 with six carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

 atoms.

The term may refer to any of four other structural isomers with that formula, or to a mixture of them. In the IUPAC
International Union of Pure and Applied Chemistry
The International Union of Pure and Applied Chemistry is an international federation of National Adhering Organizations that represents chemists in individual countries. It is a member of the International Council for Science . The international headquarters of IUPAC is located in Zürich,...

 nomenclature, however, hexane is the unbranched isomer (n-hexane); the other four structures are named as methyl
Methyl group
Methyl group is a functional group derived from methane, containing one carbon atom bonded to three hydrogen atoms —CH3. The group is often abbreviated Me. Such hydrocarbon groups occur in many organic compounds. The methyl group can be found in three forms: anion, cation and radical. The anion...

ated derivatives of pentane and butane. IUPAC also uses the term as the root of many compounds with a linear six-carbon backbone, such as 2-methylhexane
2-Methylhexane
2-Methylhexane is an isomer of heptane. It is structurally a hexane molecule with a methyl group attached to its second carbon atom...

 C7H16, which is also called "isoheptane".

Hexanes are significant constituents of gasoline
Gasoline
Gasoline , or petrol , is a toxic, translucent, petroleum-derived liquid that is primarily used as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Some gasolines also contain...

. They are all colorless liquids at room temperature, with boiling points between 50 and 70 °C, with gasoline-like odor. They are widely used as cheap, relatively safe, largely unreactive, and easily evaporated non-polar
Chemical polarity
In chemistry, polarity refers to a separation of electric charge leading to a molecule or its chemical groups having an electric dipole or multipole moment. Polar molecules interact through dipole–dipole intermolecular forces and hydrogen bonds. Molecular polarity is dependent on the difference in...

 solvent
Solvent
A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...

s.

Isomers

Common name IUPAC name Text formula Skeletal formula
normal hexane
n-hexane
hexane CH3(CH2)4CH3
isohexane 2-methylpentane
2-Methylpentane
2-Methylpentane is a branched-chain alkane with the molecular formula C6H14. It is a structural isomer of hexane composed of a methyl group bonded to the second carbon atom in a pentane chain. It is of similar structure to one of its isomers, 3-methylpentane, which has the methyl group located on...

(CH3)2CH(CH2)2CH3
3-methylpentane
3-Methylpentane
3-Methylpentane is a branched-chain alkane with the molecular formula C6H14. It is a structural isomer of hexane composed of a methyl group bonded to the third carbon atom in a pentane chain. It is of similar structure to the isomeric 2-methylpentane, which has the methyl group located on the...

CH3CH2CH(CH3)CH2CH3
2,3-dimethylbutane
2,3-Dimethylbutane
2,3-Dimethylbutane, also known as diisopropyl, is an isomer of hexane. It has the chemical formula 2CHCH2 It is a colorless liquid which boils at 57.9 °C....

CH3CH(CH3)CH(CH3)CH3
neohexane 2,2-dimethylbutane
2,2-Dimethylbutane
2,2-Dimethylbutane, trivially known as neohexane, is an organic compound with formula C6H14 or 3-C-CH2-CH3. It is therefore an alkane, indeed the most compact and branched of the hexane isomers — the only one with a quaternary carbon and a butane backbone.-See also:*methylbutane...

CH3C(CH3)2CH2CH3

Uses

In industry, hexanes are used in the formulation of glue
Adhesive
An adhesive, or glue, is a mixture in a liquid or semi-liquid state that adheres or bonds items together. Adhesives may come from either natural or synthetic sources. The types of materials that can be bonded are vast but they are especially useful for bonding thin materials...

s for shoes, leather products, and roofing. They are also used to extract cooking oil
Cooking oil
Cooking oil is purified fat of plant origin, which is usually liquid at room temperature ....

s from seeds, for cleansing and degreasing all sorts of items, and in textile manufacturing.

A typical laboratory use of hexanes is to extract oil
Petroleum
Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...

 and grease
Grease (lubricant)
The term grease is used to describe semisolid lubricants. Although the word grease is also used to describe rendered fat of animals, in the context of lubrication, grease typically applies to a material consisting of a soap emulsified with mineral or vegetable oil...

 contaminants from water and soil for analysis. Since hexane cannot be easily deprotonated
Deprotonation
Deprotonation is the removal of a proton from a molecule, forming the conjugate base.The relative ability of a molecule to give up a proton is measured by its pKa value. A low pKa value indicates that the compound is acidic and will easily give up its proton to a base...

, it is used in the laboratory for reactions that involve very strong bases, such as the preparation of organolithium
Organolithium reagent
An organolithium reagent is an organometallic compound with a direct bond between a carbon and a lithium atom. As the electropositive nature of lithium puts most of the charge density of the bond on the carbon atom, effectively creating a carbanion, organolithium compounds are extremely powerful...

s, e.g. Butyllithiums are typically supplied as a hexane solution.

In many applications (especially pharmaceutical), the use of n-hexane is being phased out due to its long term toxicity, and often replaced by n-heptane, which will not form the toxic (hexane-2,5-dione) metabolite.

Production

Hexanes are chiefly obtained by the refining
Oil refinery
An oil refinery or petroleum refinery is an industrial process plant where crude oil is processed and refined into more useful petroleum products, such as gasoline, diesel fuel, asphalt base, heating oil, kerosene, and liquefied petroleum gas...

 of crude oil
Petroleum
Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...

. The exact composition of the fraction depends largely on the source of the oil (crude or reformed) and the constraints of the refining. The industrial product (usually around 50% by weight of the straight-chain isomer) is the fraction boiling at 65–70 °C.

Physical properties

The boiling points of the various hexanes are somewhat similar and, as for other alkanes, are generally lower for the more branched forms. The melting points are quite different and the trend is not apparent.
Isomer M.P.
Melting point
The melting point of a solid is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard atmospheric pressure...

 (°C)
B.P.
Boiling point
The boiling point of an element or a substance is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid....

 (°C)
n-hexane −95.3 68.7
3-methylpentane −118.0 63.3
2-methylpentane (isohexane) −153.7 60.3
2,3-dimethylbutane −128.6 58.0
2,2-dimethylbutane (neohexane) −99.8 49.7


Normal hexane has considerable vapor pressure at room temperature:
temperature (°C) vapor pressure (mmHg)
−40 3.36
−30 7.12
−20 14.01
−10 25.91
0 45.37
10 75.74
20 121.26
25 151.28
30 187.11
40 279.42
50 405.31
60 572.76

Toxicity

The acute toxicity
Toxicity
Toxicity is the degree to which a substance can damage a living or non-living organisms. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell or an organ , such as the liver...

 of hexane is relatively low, although it is a mild anesthetic. Inhalation of high concentrations produces first a state of mild euphoria
Euphoria (emotion)
Euphoria is medically recognized as a mental and emotional condition in which a person experiences intense feelings of well-being, elation, happiness, ecstasy, excitement and joy...

, followed by somnolence
Somnolence
Somnolence is a state of near-sleep, a strong desire for sleep, or sleeping for unusually long periods . It has two distinct meanings, referring both to the usual state preceding falling asleep, and the chronic condition referring to being in that state independent of a circadian rhythm...

 with headache
Headache
A headache or cephalalgia is pain anywhere in the region of the head or neck. It can be a symptom of a number of different conditions of the head and neck. The brain tissue itself is not sensitive to pain because it lacks pain receptors. Rather, the pain is caused by disturbance of the...

s and nausea
Nausea
Nausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...

.

The long-term toxicity
Toxicity
Toxicity is the degree to which a substance can damage a living or non-living organisms. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell or an organ , such as the liver...

 of n-hexane in humans is well known. Extensive peripheral nervous system failure
Polyneuropathy
Polyneuropathy is a neurological disorder that occurs when many peripheral nerves throughout the body malfunction simultaneously. It may be acute and appear without warning, or chronic and develop gradually over a longer period of time. Many polyneuropathies have both motor and sensory...

 is known to occur in humans chronically exposed to levels of n-hexane ranging from 400 to 600 ppm
Parts-per notation
In science and engineering, the parts-per notation is a set of pseudo units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they are pure numbers with no associated units of measurement...

, with occasional exposures up to 2,500 ppm. The initial symptoms are tingling and cramps in the arms and legs, followed by general muscular weakness. In severe cases, atrophy
Atrophy
Atrophy is the partial or complete wasting away of a part of the body. Causes of atrophy include mutations , poor nourishment, poor circulation, loss of hormonal support, loss of nerve supply to the target organ, disuse or lack of exercise or disease intrinsic to the tissue itself...

 of the skeletal muscle
Skeletal muscle
Skeletal muscle is a form of striated muscle tissue existing under control of the somatic nervous system- i.e. it is voluntarily controlled. It is one of three major muscle types, the others being cardiac and smooth muscle...

s is observed, along with a loss of coordination and problems of vision. Similar symptoms are observed in animal models. They are associated with a degeneration of the peripheral nervous system
Peripheral nervous system
The peripheral nervous system consists of the nerves and ganglia outside of the brain and spinal cord. The main function of the PNS is to connect the central nervous system to the limbs and organs. Unlike the CNS, the PNS is not protected by the bone of spine and skull, or by the blood–brain...

 (and eventually the central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...

), starting with the distal portions of the longer and wider nerve axon
Axon
An axon is a long, slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neuron's cell body or soma....

s. The toxicity is not due to hexane itself but to one of its metabolite
Metabolite
Metabolites are the intermediates and products of metabolism. The term metabolite is usually restricted to small molecules. A primary metabolite is directly involved in normal growth, development, and reproduction. Alcohol is an example of a primary metabolite produced in large-scale by industrial...

s, hexane-2,5-dione
Hexane-2,5-dione
Hexane-2,5-dione, C6H10O2, is a diketone and a toxic metabolite of hexane.-Symptoms:The initial symptoms of chronic hexane toxicity, attributable to hexane-2,5-dione, are tingling and cramps in the arms and legs, followed by general muscular weakness...

. It is believed that this reacts with the amino group of the side chain
Side chain
In organic chemistry and biochemistry, a side chain is a chemical group that is attached to a core part of the molecule called "main chain" or backbone. The placeholder R is often used as a generic placeholder for alkyl group side chains in chemical structure diagrams. To indicate other non-carbon...

 of lysine
Lysine
Lysine is an α-amino acid with the chemical formula HO2CCH4NH2. It is an essential amino acid, which means that the human body cannot synthesize it. Its codons are AAA and AAG....

 residues in protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

s, causing cross-link
Cross-link
Cross-links are bonds that link one polymer chain to another. They can be covalent bonds or ionic bonds. "Polymer chains" can refer to synthetic polymers or natural polymers . When the term "cross-linking" is used in the synthetic polymer science field, it usually refers to the use of...

ing and a loss of protein function.

Chronic intoxication from hexane has been observed in recreational solvent abusers
Inhalant
Inhalants are a broad range of drugs whose volatile vapors are taken in via the nose and trachea. They are taken by volatilization, and do not include drugs that are inhaled after burning or heating...

 and in workers in the shoe
Shoe
A shoe is an item of footwear intended to protect and comfort the human foot while doing various activities. Shoes are also used as an item of decoration. The design of shoes has varied enormously through time and from culture to culture, with appearance originally being tied to function...

 manufacturing, furniture restoration
Antiques restoration
Antiques restoration refers to either the practice of "restoration"- restoring an antique or work of art to a like-new condition , or "conservation"- the practice of preserving an antique or work of art against further deterioration.-Restoration:Restoration can be as simple as light cleaning to...

 and automobile
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...

 construction industries, and recently, plastic recyclers and assemblers and cleaners of capacitive touch-screen devices.

In 1994, n-hexane was included in the list of chemicals on the US Toxic Release Inventory (TRI). In 2001, the U.S. Environmental Protection Agency issued regulations on the control of emissions of hexane gas due to its potential carcinogenic properties and environmental concerns.

Use in food processing

According to a report by the Cornucopia Institute
Cornucopia Institute
The Cornucopia Institute is a non-profit organization headquartered in Cornucopia, Wisconsin, with the mission of "Seeking economic justice for the family-scale farming community."...

, hexane is used to extract oil from grains as well as protein from soy, to such an extent that in 2007, grain processors were responsible for more than two-thirds of hexane emissions in the United States. The report also pointed out that the hexane can persist in the final food product created; in a sample of processed soy, the oil contained 10 ppm, the meal 21 ppm and the grits 14 ppm hexane. The adverse health effects seem specific to n-hexane; they are much reduced or absent for other isomers. Therefore, the food oil extraction industry, which relied heavily on hexane, has been considering switching to other solvents, including isohexane.

Poisoning from touchscreen cleaner

In February 2010, reports surfaced saying that an employee of Wintek Corporation
Wintek
Wintek is a maker of electronic components, mainly touch screens for devices such as Apple's iPhone.-History:Wintek was established in 1990 and produces components in China, Taiwan and India.-Worker illness controversy:...

 in China, a company that manufactures touchscreen components, died in August 2009 due to hexane poisoning. Hexane was used as a replacement for alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....

 for cleaning the screens. Reports suggest up to 137 Chinese employees required treatment for hexane poisoning around the same time. An ABC
Australian Broadcasting Corporation
The Australian Broadcasting Corporation, commonly referred to as "the ABC" , is Australia's national public broadcaster...

 Foreign Correspondent
Foreign Correspondent (TV series)
Foreign Correspondent is a weekly Australian documentary series and current affairs program screened on ABC1, Tuesday at . Premiering at on Saturday 14 March 1992, the aim is to give informed information about the happenings in other countries either on the light side of life or during crisis.-...

 episode covertly interviewed several women who had been in the hospital for over six months. The women claimed that they were exposed to hexane while manufacturing iPhone
IPhone
The iPhone is a line of Internet and multimedia-enabled smartphones marketed by Apple Inc. The first iPhone was unveiled by Steve Jobs, then CEO of Apple, on January 9, 2007, and released on June 29, 2007...

hardware.

External links



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