hexane

Hexane
Other names	n-Hexane
Identifiers
CAS number	110-54-3 Y
PubChem	8058
RTECS number	MN9275000
SMILES	CCCCCC
InChI	1/C6H14/c1-3-5-6-4-2/h3-6H2,1-2H3
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
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
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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].

Isomers

Hexane has five isomers:^[3]

• 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.

Physical Properties

The vapor pressure of hexane rises rapidly with temperature, reaching atmospheric pressure at its boiling point.

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.

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]

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]

See also

• Cyclohexane
• Hexene

"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

References

1. ^ http://www.inchem.org/documents/icsc/icsc/eics0279.htm
2. ^ Use of ozone depleting substances in laboratories. TemaNord 2003:516. http://www.norden.org/pub/ebook/2003-516.pdf
3. ^ "C5 and C6 alkanes". A and B Scott Organic Chemistry. http://members.optushome.com.au/scottsoftb/skeletons2.htm. Retrieved 2007-10-30. 
4. ^ 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. 
5. ^ "N-Hexane Chemical Backgrounder". National Safety Council. http://www.nsc.org/ehc/chemical/N-Hexane.htm. Retrieved 25 May 2007. 
6. ^ 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. 
7. ^ 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]
8. ^ Isohexane—New Solvent for Cottonseed Oil Processing

• Institut national de recherche et de sécurité. (2005). "Hexane". Fiche toxicologique n° 113, 8pp. (in French)

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