Hexane

Not to be confused with hexene or hexyne.

Hexane

Skeletal formula of hexane
Skeletal formula of hexane with all implicit carbons shown, and all explicit hydrogens added
Ball and stick model of hexane
Spacefill model of hexane
Names
IUPAC name Hexane
Identifiers
CAS Number	110-54-3 Y
Beilstein Reference	1730733
ChEBI	CHEBI:29021 Y
ChEMBL	ChEMBL15939 Y
ChemSpider	7767 Y
DrugBank	DB02764 Y
EC Number	203-777-6
Gmelin Reference	1985
Jmol 3D model	Interactive image
KEGG	C11271 Y
MeSH	n-hexane
PubChem	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	86.18 g·mol−1
Appearance	Colorless liquid
Odor	Petrolic
Density	0.6548 g mL−1
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
Refractive index (nD)	1.375
Viscosity	0.3 mPa · s
Thermochemistry
Specific 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
Vapor pressure	{{{value}}}
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
Y verify (what is YN ?)
Infobox references

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. In IUPAC nomenclature, however, hexane is the unbranched isomer (n-hexane); the other four structures 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 (C₇H₁₆), which is also called "isoheptane".

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

Isomers

Common name	IUPAC name	Text formula	Skeletal formula
normal hexane n-hexane	hexane	CH3(CH2)4CH3	150px
isohexane	2-methylpentane	(CH3)2CH(CH2)2CH3	110px
	3-methylpentane	CH3CH2CH(CH3)CH2CH3	110px
	2,3-dimethylbutane	CH3CH(CH3)CH(CH3)CH3	90px
neohexane	2,2-dimethylbutane	CH3C(CH3)2CH2CH3	90px

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. It is commonly used in food based soybean oil extraction in the United States, and it is a contaminant potentially present in all soy food products using the technique, which is controversially not regulated by the FDA.

A typical laboratory use of hexanes is to extract oil and grease contaminants from water and soil for analysis. 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.

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.

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

Production

Hexanes are chiefly obtained by the refining of 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.

Physical properties

All alkanes are colorless. 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. (°C)	B.P. (°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

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

Safety

Acute exposure to n-hexane usually occurs by inhalation, but it may be absorbed orally and transdermally. Minor exposures may occur when people fill their automobile fuel tanks with gasoline. Recent research suggests that certain fungi may be able to produce n-hexane.

The acute toxicity of n-hexane is rather low. However, it has been reported to be the most highly toxic member of the alkanes. When n-hexane is ingested, it causes nausea, vertigo, bronchial irritation, intestinal irritation and CNS effects. It has been reported that ~50 g of n-hexane may be fatal to humans. Furthermore, n-hexane is biotransformed to 2-hexanol and further to 2,5-hexanediol by cytochrome P450 mixed function oxidases by omega oxidation. 2,5-Hexanediol may be further oxidized to 2,5-hexanedione, which is neurotoxic and produces a polyneuropathy.

Products with low viscosity such as hexane and other volatile hydrocarbons (petroleum ether) present an extreme aspiration risk. Even small amounts of a low-viscosity material, once aspirated, can involve a significant portion of the lung and produce a chemical pneumonitis. Hydrocarbon pneumonia is an acute hemorrhagic necrotizing disease that can develop within 24 h after the ingestion. Pneumonia may require several weeks for complete resolution. Therefore, gastric lavage is not indicated for hydrocarbon ingestion because of the risk of aspiration if the patient vomits around the lavage tube.

n-Hexane is also used as a solvent in the extraction of oil from seeds (soybean, cottonseed, flaxseed, safflower seed, and others). It 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 less toxic solvents.

A peer reviewed study found that 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. 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) over an 8-hour workday.

Occupational hexane poisoning has occurred with Japanese sandal workers, Italian shoe workers, Taiwan press proofing workers, and others. Analysis of Taiwanese workers has shown occupational exposure to substances including n-hexane. In 2010-2011, Chinese workers manufacturing iPhones were reported as having suffered hexane poisoning.

External links

• International Chemical Safety Card 1262 (2-methylpentane)
• Material Safety Data Sheet for Hexane
• National Pollutant Inventory – n-hexane fact sheet
• NIOSH Pocket Guide to Chemical Hazards (hexane isomers)
• 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