Hexane
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| Names | |
|---|---|
| IUPAC name
Hexane[1]
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| Identifiers | |
| 1730733 | |
| CAS number | 110-54-3  |
| ChEBI | CHEBI:29021 |
| ChEMBL | ChEMBL15939 |
| ChemSpider | 7767 |
| DrugBank | DB02764 |
| EC number | 203-777-6 |
| 1985 | |
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| Jmol-3D images | Image |
| KEGG | C11271 |
| MeSH | n-hexane |
| PubChem | 8058 |
| RTECS number | MN9275000 |
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| UNII | 2DDG612ED8 |
| UN number | 1208 |
| Properties | |
| C6H14 | |
| Molar mass | 86.18 g·mol−1 |
| Appearance | Colorless liquid |
| Odor | Petrolic |
| Density | 0.6548 g mL−1 |
| Melting point | −96 °C; −141 °F; 177 K |
| Boiling point | 68.5 °C; 155.2 °F; 341.6 K |
| 9.5 mg L−1 | |
| log P | 3.764 |
| Vapor pressure | 17.60 kPa (at 20.0 °C) |
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Henry's law
constant (kH) |
7.6 nmol Pa−1 kg−1 |
| UV-vis (λmax) | 200 nm |
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Refractive index (nD)
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1.375 |
| Viscosity | 294 μPa s |
| Thermochemistry | |
| 265.2 J K−1 mol−1 | |
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Std molar
entropy (S |
296.06 J K−1 mol−1 |
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Std enthalpy of
formation (ΔfH |
−199.4–−198.0 kJ mol−1 |
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Std enthalpy of
combustion (ΔcH |
−4180–−4140 kJ mol−1 |
| Hazards | |
| MSDS | External MSDS |
| GHS pictograms |     |
| GHS signal word | DANGER |
| H225, H304, H315, H336, H373, H411 | |
| P210, P261, P273, P281, P301+310, P331 | |
| EU Index | 601-037-00-0 |
| EU classification |  F  Xn  N |
| R-phrases | R11, R38, R48/20, R51/53, R62, R65, R67 |
| S-phrases | (S2), S16, S29, S33, S36/37 |
| NFPA 704 | |
| Flash point | −26.0 °C (−14.8 °F; 247.2 K) |
| 234.0 °C (453.2 °F; 507.1 K) | |
| Explosive limits | 1.2–7.7% |
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LD50 (Lethal dose)
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25 g kg−1 (oral, rat) |
| US health exposure limits (NIOSH): | |
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PEL (Permissible)
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500 ppm (1800 mg m−3 as an 8 h TWA) |
| Related compounds | |
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Related alkanes
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| Supplementary data page | |
| Refractive index (n), Dielectric constant (εr), etc. |
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Thermodynamic
data |
Phase behaviour solid–liquid–gas |
| UV, IR, NMR, MS | |
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Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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 verify (what is:  / ?) |
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| 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.[2] 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[edit]
| 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 |  |
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| 2,3-dimethylbutane | CH3CH(CH3)CH(CH3)CH3 |  |
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| neohexane | 2,2-dimethylbutane | CH3C(CH3)2CH2CH3 |  |
Uses[edit]
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.[3][4]
A typical laboratory use of hexanes is to extract oil and grease contaminants from water and soil for analysis.[5] 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.
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.[6]
Production[edit]
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[edit]
All alkanes are colorless.[7][8] 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.[9]
| 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:[10]
| 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[edit]
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.[11]
The acute toxicity of n-hexane is rather low. However, it has been reported to be the most highly toxic member of the alkanes.[citation needed] 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.[11]
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.[11]
The National Institute for Occupational Safety and Health recommended exposure limit is 50 ppm (180 mg m−3), expressed as an 8 h time-weighted average (TWA).[11] 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.[12]
Occupational hexane poisoning has occurred with Japanese sandal workers, Italian shoe workers,[13] Taiwan press proofing workers, and others.[14] Analysis of Taiwanese workers has shown occupational exposure to substances including n-hexane.[15] In 2010-2011, Chinese workers manufacturing iPhones were reported as having suffered hexane poisoning.[16][17]
References[edit]
- ^ "n-hexane – Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 16 September 2004. Identification and Related Records. Retrieved 31 December 2011.
- ^ "C5 and C6 alkanes". A and B Scott Organic Chemistry. Retrieved 30 October 2007.
- ^ http://www.tofurky.com/ourstory/ingred_hexane.html
- ^ http://www.slate.com/articles/news_and_politics/explainer/2010/04/is_your_veggie_burger_killing_you.html
- ^ Use of ozone depleting substances in laboratories. TemaNord 2003:516.
- ^ Filser JG, Csanády GA, Dietz W, Kessler W, Kreuzer PE, Richter M, Störmer A (1996). "Comparative estimation of the neurotoxic risks of n-hexane and n-heptane in rats and humans based on the formation of the metabolites 2,5-hexanedione and 2,5-heptanedione". Adv Exp Med Biol 387: 411–427. PMID 8794236.
- ^ "Organic Chemistry-I" (PDF). Retrieved 2014-02-17.
- ^ "13. Hydrocarbons | Textbooks". Textbook.s-anand.net. Retrieved 2014-02-17.
- ^ William D. McCain (1990). The properties of petroleum fluids. PennWell. ISBN 0-87814-335-1.
- ^ vapor pressure
- ^ a b c d Stephen R Clough; Leyna Mulholland (2005), "Hexane", Encyclopedia of Toxicology 2 (2nd ed.), Elsevier, pp. 522–525
- ^ "N-HEXANE". Toxicology data network Hazardous Substances Data Bank. National Library of Medicine.
- ^ Rizzuto, N; De Grandis, D; Di Trapani, G; Pasinato, E (1980). "N-hexane polyneuropathy. An occupational disease of shoemakers". European neurology 19 (5): 308–15. PMID 6249607.
- ^ n-Hexane, Environmental Health Criteria (122), World Health Organization, 1991
- ^ Liu, C. H.; Huang, C. Y.; Huang, C. C. (2012). "Occupational Neurotoxic Diseases in Taiwan". Safety and Health at Work 3 (4): 257–67. doi:10.5491/SHAW.2012.3.4.257. PMC 3521924. PMID 23251841.
- ^ Workers poisoned while making iPhones ABC News, 25 October 2010
- ^ David Barboza (Feb 22, 2011). "Workers Sickened at Apple Supplier in China". New York Times.
External links[edit]
- 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
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