Hexane
From Wikipedia, the free encyclopedia
| Hexane | |
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| Other names | n-Hexane |
| Identifiers | |
| CAS number | 110-54-3  |
| PubChem | 8058 |
| RTECS number | MN9275000 |
| SMILES |
CCCCCC
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| InChI |
1/C6H14/c1-3-5-6-4-2/h3-6H2,1-2H3
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| ChemSpider ID | 7767 |
| Properties | |
| Molecular formula | C6H14 |
| Molar mass | 86.18 g/mol |
| Appearance | Colorless liquid |
| Density | 0.6548 g/ml, liquid |
| Melting point |
−95 °C (178 K) |
| Boiling point |
69 °C (342 K) |
| Solubility in water | 13 mg/l at 20°C[1] |
| Viscosity | 0.294 cP at 25 °C |
| Hazards | |
| MSDS | External MSDS |
| EU classification | Flammable (F) Harmful (Xn) Repr. Cat. 3 Dangerous for the environment (N) |
| R-phrases | R11, R38, R48/20, R62, R65, R67, R51/53 |
| S-phrases | (S2), S9, S16, S29, S33, S36/37, S61, S62 |
| NFPA 704 |
 3
1
0
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| Flash point | −23.3 °C |
| Autoignition temperature |
233.9 °C |
| Related compounds | |
| Related alkanes | Pentane Heptane |
| Related compounds | Cyclohexane |
| Supplementary data page | |
| Structure and properties |
n, εr, etc. |
| Thermodynamic data |
Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| (what is this?) (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Hexane is an alkane hydrocarbon with the chemical formula CH3(CH2)4CH3 or C6H14. The "hex" prefix refers to its six carbons, while the "ane" ending indicates that its carbons are connected by single bonds. Hexane isomers are largely unreactive, and are frequently used as an inert solvent in organic reactions because they are very non-polar. They are also common constituents of gasoline and glues used for shoes, leather products, and roofing. Additionally, it is used in solvents to extract oils for cooking and as a cleansing agent for shoe, furniture and textile manufacturing. In laboratories, hexane is used to extract oil and grease from water and soil before determination by gravimetric analysis or gas chromatography[2].
Contents |
[edit] Isomers
- Hexane, CH3CH2CH2CH2CH2CH3, a straight chain of six carbon atoms.
- 2-Methylpentane (Isohexane), CH3CH(CH3)CH2CH2CH3, a five-carbon chain with one methyl branch on the second.
- 3-Methylpentane, CH3CH2CH(CH3)CH2CH3, a five-carbon chain with one methyl branch on the third.
- 2,3-Dimethylbutane, CH3CH(CH3)CH(CH3)CH3, a four-carbon chain with one methyl branch on the second and third.
- 2,2-Dimethylbutane (neohexane) , CH3C(CH3)2CH2CH3, a four-carbon chain with two methyl branches on the second.
[edit] Physical Properties
The vapor pressure of hexane rises rapidly with temperature, reaching atmospheric pressure at its boiling point.
| 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 |
[edit] Production
Hexane is produced 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.
[edit] Toxicity
The acute toxicity of hexane is relatively low, although it is a mild anesthetic. Inhalation of high concentrations produces first a state of mild euphoria, followed by somnolence with headaches and nausea.
Chronic intoxication from hexane has been observed in recreational solvent abusers and in workers in the shoe manufacturing, furniture restoration and automobile construction industries. The initial symptoms are tingling and cramps in the arms and legs, followed by general muscular weakness. In severe cases, atrophy of the skeletal muscles is observed, along with a loss of coordination and problems of vision.
The neuropathic toxicity of n-hexane in humans is well known[4] ; cases of polyneuropathy have typically occurred in humans chronically exposed to levels of n-hexane ranging from 400 to 600 ppm, with occasional exposures up to 2,500 ppm.
Similar symptoms are observed in animal models. They are associated with a degeneration of the peripheral nervous system (and eventually the central nervous system), starting with the distal portions of the longer and wider nerve axons. The toxicity is not due to hexane itself but to one of its metabolites, hexane-2,5-dione. It is believed that this reacts with the amino group of the side chain of lysine residues in proteins, causing cross-linking and a loss of protein function.
The effects of hexane poisoning in humans are uncertain. In 1994, n-hexane was included in the list of chemicals on the Toxic Release Inventory (TRI).[5] In the latter part of the 20th and early part of the 21st centuries, a number of explosions have been attributed to the combustion of hexane gas. 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.[6]
[edit] Extraction of vegetable oils
Concerns about n-hexane's toxicity have lead to efforts to find new solvents for lipid extraction for food oils; a process for which hexane's use was ubiquitous.[7] Isohexane is a favoured replacement.[8]
[edit] See also
"EPA does not consider n-hexane classifiable as a human carcinogen." Federal Register / Vol. 66, No. 71 / Thursday, April 12, 2001 / Rules and Regulations
http://www.epa.gov/ttn/atw/vegoil/fr12ap01.pdf
[edit] References
- ^ http://www.inchem.org/documents/icsc/icsc/eics0279.htm
- ^ Use of ozone depleting substances in laboratories. TemaNord 2003:516. http://www.norden.org/pub/ebook/2003-516.pdf
- ^ "C5 and C6 alkanes". A and B Scott Organic Chemistry. http://members.optushome.com.au/scottsoftb/skeletons2.htm. Retrieved 2007-10-30.
- ^ Hathaway GJ, Proctor NH, Hughes JP, and Fischman M (1991). Proctor and Hughes' chemical hazards of the workplace. 3rd ed. New York, NY: Van Nostrand Reinhold.
- ^ "N-Hexane Chemical Backgrounder". National Safety Council. http://www.nsc.org/ehc/chemical/N-Hexane.htm. Retrieved 25 May 2007.
- ^ Anuradee Witthayapanyanon and Linh Do. "Nanostructured Microemulsions as Alternative Solvents to VOCs in Cleaning Technologies and Vegetable Oil Extraction". National Center For Environmental Research. http://es.epa.gov/ncer/publications/meetings/10_26_05/abstracts/do.html. Retrieved 25 May 2007.
- ^ Technology and solvents for extracting oilseeds and nonpetroleum oils By Peter J. Wan, Phillip J. Wakelyn p189 [Google books : http://books.google.co.uk/books?id=jqUjKBplqPcC&lpg=PP1&pg=PA189#v=onepage&q=&f=false]
- ^ Isohexane—New Solvent for Cottonseed Oil Processing
- Institut national de recherche et de sécurité. (2005). "Hexane". Fiche toxicologique n° 113, 8pp. (in French)
[edit] External links
- International Chemical Safety Card 0279 (n-hexane)
- 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
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