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Hexane /ˈhɛkseɪn/ is an alkane of six carbon atoms, with the chemical formula C₆H₁₄.

The term may refer to any of the five structural isomers with that formula, or to a mixture of them.^[7] In IUPAC nomenclature, however, hexane is the unbranched isomer (n-hexane); the other four isomers are named as methylated 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.

Hexanes are significant constituents of gasoline. They are all colorless liquids, odorless when pure, with boiling points between 50 and 70 °C (122 and 158 °F). They are widely used as cheap, relatively safe, largely unreactive, and easily evaporated non-polar solvents.

Isomers

Hexane

Names
IUPAC name Hexane[2]
Other names Sextane[1]
Identifiers
CAS Number	110-54-3 Y
3D model (JSmol)	Interactive image
Beilstein Reference	1730733
ChEBI	CHEBI:29021 Y
ChEMBL	ChEMBL15939 Y
ChemSpider	7767 Y
DrugBank	DB02764 Y
ECHA InfoCard	100.003.435
EC Number	203-777-6
Gmelin Reference	1985
KEGG	C11271 Y
MeSH	n-hexane
PubChem CID	8058
RTECS number	MN9275000
UNII	2DDG612ED8 Y
UN number	1208
InChI InChI=1S/C6H14/c1-3-5-6-4-2/h3-6H2,1-2H3 Y Key: VLKZOEOYAKHREP-UHFFFAOYSA-N Y
SMILES CCCCCC
Properties
Chemical formula	C6H14
Molar mass	7001861780000000000♠86.178 g·mol−1
Appearance	Colorless liquid
Odor	Petrolic
Density	0.6606 g mL−1[3]
Melting point	−96 to −94 °C; −141 to −137 °F; 177 to 179 K
Boiling point	68.5 to 69.1 °C; 155.2 to 156.3 °F; 341.6 to 342.2 K
Solubility in water	9.5 mg L−1
log P	3.764
Vapor pressure	17.60 kPa (at 20.0 °C)
Henry's law constant (kH)	7.6 nmol Pa−1 kg−1
UV-vis (λmax)	200 nm
Magnetic susceptibility (χ)	−74.6·10−6 cm3/mol
Refractive index (nD)	1.375
Viscosity	0.3 mPa·s
Thermochemistry
Heat capacity (C)	265.2 J K−1 mol−1
Std molar entropy (So298)	296.06 J K−1 mol−1
Std enthalpy of formation (ΔfHo298)	−199.4–−198.0 kJ mol−1
Std enthalpy of combustion (ΔcHo298)	−4180–−4140 kJ mol−1
Hazards
Main hazards	Reproductive toxicity – After aspiration, pulmonary oedema, pneumonitis, and death [4]
Safety data sheet	See: data page
GHS pictograms
GHS signal word	DANGER
GHS hazard statements	H225, H304, H315, H336, H361fd, H373, H401, H411
GHS precautionary statements	P201, P202, P210, P233, P240, P241, P242, P243, P260, P264, P271, P273, P280, P281, P301+330+331, P310, P302+352, P303+361+353, P304+340, P312, P308+313, P314, P332+313, P363, P370+378
NFPA 704
Flash point	−26.0 °C (−14.8 °F; 247.2 K)
Autoignition temperature	234.0 °C (453.2 °F; 507.1 K)
Explosive limits	1.2–7.7%
Lethal dose or concentration (LD, LC):
LD50 (median dose)	25 g kg−1(oral, rat) 28710 mg/kg (rat, oral)[6]
LDLo (lowest published)	56137 mg/kg (rat, oral)[6]
US health exposure limits (NIOSH):
PEL (Permissible)	TWA 500 ppm (1800 mg/m3)[5]
REL (Recommended)	TWA 50 ppm (180 mg/m3)[5]
IDLH (Immediate danger)	1100 ppm[5]
Related compounds
Related alkanes	Pentane Heptane
Supplementary data page
Structure and properties	Refractive index (n), Dielectric constant (εr), etc.
Thermodynamic data	Phase behaviour solid–liquid–gas
Spectral data	UV, IR, NMR, MS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Common name	IUPAC name	Text formula	Skeletal formula
normal hexane n-hexane	hexane	CH3(CH2)4CH3
isohexane	2-methylpentane	(CH3)2CH(CH2)2CH3
	3-methylpentane	CH3CH2CH(CH3)CH2CH3
	2,3-dimethylbutane	(CH3)2CHCH(CH3)2
neohexane	2,2-dimethylbutane	(CH3)3CCH2CH3

Uses

In industry, hexanes are used in the formulation of glues for shoes, leather products, and roofing. They are also used to extract cooking oils (such as canola oil or soy oil) from seeds, for cleansing and degreasing a variety of items, and in textile manufacturing. They are commonly used in food based soybean oil extraction in the United States, and are potentially present as contaminants in all soy food products in which the technique is used; the lack of regulation by the FDA of this contaminant is a matter of some controversy.^[8][9]

A typical laboratory use of hexanes is to extract oil and grease contaminants from water and soil for analysis.^[10] Since hexane cannot be easily deprotonated, it is used in the laboratory for reactions that involve very strong bases, such as the preparation of organolithiums. For example, butyllithiums are typically supplied as a hexane solution.^{[citation needed]}

Hexanes are commonly used in chromatography as a non-polar solvent. Higher alkanes present as impurities in hexanes have similar retention times as the solvent, meaning that fractions containing hexane will also contain these impurities. In preparative chromatography, concentration of a large volume of hexanes can result in a sample that is appreciably contaminated by alkanes. This may result in a solid compound being obtained as an oil and the alkanes may interfere with analysis.^{[citation needed]}

Production

Hexanes are chiefly obtained by refining crude oil. 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 (149–158 °F).

Physical properties

All alkanes are colorless.^[11][12] 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.^[13]

Hexane has considerable vapor pressure at room temperature:

Reactivity

Like most alkanes, hexane characteristically exhibits low reactivity and are suitable solvents for reactive compounds. Commercial samples of n-hexane however often contains methylcyclopentane, which features tertiary C-H bonds, which are incompatible with some radical reactions.^[14]

Safety

The acute toxicity of n-hexane is rather low, requiring grams per kilogram. Inhalation of n-hexane at 5000 ppm for 10 minutes produces marked vertigo; 2500-1000 ppm for 12 hours produces drowsiness, fatigue, loss of appetite, and paresthesia in the distal extremities; 2500–5000 ppm produces muscle weakness, cold pulsation in the extremities, blurred vision, headache and anorexia.^[15] The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) for hexane isomers (not n-hexane) of 100 ppm (350 mg/m³ (0.15 gr/cu ft)) over an 8-hour workday.^[16]

Hexane and other volatile hydrocarbons (petroleum ether) present an aspiration risk.^[17]n-Hexane is sometimes used as a denaturant for alcohol, and as a cleaning agent in the textile, furniture, and leather industries. It is slowly being replaced with other solvents.^[18]

Like gasoline, hexane is highly volatile and is an explosion risk.

Incidents

Occupational hexane poisoning has occurred with Japanese sandal workers, Italian shoe workers,^[19]Taiwan press proofing workers, and others.^[20] Analysis of Taiwanese workers has shown occupational exposure to substances including n-hexane.^[21] In 2010–2011, Chinese workers manufacturing iPhones were reported to have suffered hexane poisoning.^[22][23]

Hexane was identified as being the cause of the Louisville sewer explosions on February 13, 1981, that destroyed more than 13 miles (21 km) of sewer lines and streets in the center of Louisville in Kentucky, United States

Biotransformation

n-Hexane is biotransformed to 2-hexanol and further to 2,5-hexanediol in the body. The conversion is catalyzed by the enzyme cytochrome P450 utilizing oxygen from air. The pathway is called omega oxidation. 2,5-Hexanediol may be further oxidized to 2,5-hexanedione, which is neurotoxic and produces a polyneuropathy.^[18] In view of this behavior, replacement of n-hexane as a solvent has been discussed. n-Heptane is a possible alternative.^[24]

See also

• Cyclohexane


• Louisville sewer explosions

References

External links

• 
  International Chemical Safety Card 1262 (2-methylpentane)


• Material Safety Data Sheet for Hexane


• National Pollutant Inventory – n-hexane fact sheet


• Phytochemica l database entry


• Center for Disease Control and Prevention


• Warning from National Safety Council "COMMON CHEMICAL AFFECTS AUTO MECHANICS"


• Australian National Pollutant Inventory (NPI) page


• 
  "EPA does not consider n-hexane classifiable as a human carcinogen." Federal Register / Vol. 66, No. 71 / Thursday, 12 April 2001 / Rules and Regulations