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n-Hexane
Hexane-2D-Skeletal.svg
Hexane-2D-flat-B.png
Hexane-from-xtal-1999-at-an-angle-3D-balls.png
Hexane-3D-vdW.png
Other names n-Hexane
Identifiers
CAS number 110-54-3 Yes check.svgY
PubChem 8058
RTECS number MN9275000
SMILES
InChI
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
NFPA 704.svg
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
 Yes check.svgY (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 hydrocarbon with the chemical formula C6H14; that is, an alkane with six carbon atoms.

The term may refer to any of four other structural isomers with that formula, or to a mixture of them:[2]. In the 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".

Common name IUPAC name Molecular
diagram
Skeletal
diagram
normal hexane
n-hexane
hexane Hexane-2D-flat-B.png Hexane-2D-Skeletal.svg
isohexane 2-methylpentane 2-metilpentāns.svg
  3-methylpentane 3-metilpentāns.svg
  2,3-dimethylbutane 2,3-dimetilbutāns.svg
neohexane 2,2-dimethylbutane 2,2-dimetilbutāns.svg

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

Contents

Uses

In the industry, hexanes are used in the formulation of glues for shoes, leather products, and roofing. They are also used to extract cooking oils from seeds, for cleansing and degreasing all sorts of items, and in textile manufacturing.

A typical laboratory use of hexanes to extract oil and grease contaminants from water and soil for analysis.[3]. Since hexane cannot be deprotonated, it is used in the laboratory for reactions that involve very strong bases, such as the preparation of Grignard reagents.[4]

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

The boiling points of the various hexanes are somewat 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.[5]

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

Normal hexane has considerable vapor pressure at room temperatures:

Hexane Vapor Pressure
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

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.

The long-term toxicity of n-hexane in humans is well known[6] Extensive peripheral nervous system failure is known to occur in humans chronically exposed to levels of n-hexane ranging from 400 to 600 ppm, with occasional exposures up to 2,500 ppm. 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 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.

Chronic intoxication from hexane has been observed in recreational solvent abusers and in workers in the shoe manufacturing, furniture restoration and automobile construction industries.

In 1994, n-hexane was included in the list of chemicals on the US Toxic Release Inventory (TRI).[7] 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.[8]

The adverse health effects above seem specific to n-hexane; they are much reduced or absent for other isomers.[9] Therefore, the food oil extraction industry, which relied heavily on hexane, has been considering switching to other solvents, including isohexane. [10][9]:p.189[11]

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.

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

References

  1. ^ http://www.inchem.org/documents/icsc/icsc/eics0279.htm
  2. ^ "C5 and C6 alkanes". A and B Scott Organic Chemistry. http://members.optushome.com.au/scottsoftb/skeletons2.htm. Retrieved 2007-10-30.  
  3. ^ Use of ozone depleting substances in laboratories. TemaNord 2003:516. http://www.norden.org/pub/ebook/2003-516.pdf
  4. ^ [http:it.wikipedia.org/wiki/esano esano] ("hexane") in the Italian wikipedia.
  5. ^ William D. McCain (1990), The properties of petroleum fluids. PennWell. ISBN 0878143351, 548 pages
  6. ^ 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.  
  7. ^ "N-Hexane Chemical Backgrounder". National Safety Council. http://www.nsc.org/ehc/chemical/N-Hexane.htm. Retrieved 25 May 2007.  
  8. ^ 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.  
  9. ^ a b Peter J. Wan, Phillip J. Wakelyn (1997), Technology and solvents for extracting oilseeds and nonpetroleum oils The American Oil Chemists Society. ISBN 0935315810, 353 pages.
  10. ^ USDA (1996), Isohexane—New Solvent for Cottonseed Oil Processing
  11. ^ Yuichiro Ono, Yasuhiro Takeuchi, and Naomi Hisanaga (1981), A comparative study on the toxicity of n-hexane and its isomers on the peripheral nerve. International Archives of Occupational and Environmental Health, volume 48, issue 3, pp. 289–294 doi:10.1007/BF00405616
  • Institut national de recherche et de sécurité. (2005). "Hexane". Fiche toxicologique n° 113, 8pp. (in French)

External links

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