Hexane

n-Hexane
Identifiers
CAS number 110-54-3 YesY
PubChem 8058
ChemSpider 7767 YesY
UNII 2DDG612ED8 YesY
DrugBank DB02764
KEGG C11271 YesY
ChEBI CHEBI:29021 YesY
ChEMBL CHEMBL15939 YesY
RTECS number MN9275000
Jmol-3D images Image 1
Properties
Molecular formula C6H14
Molar mass 86.18 g mol−1
Appearance Colorless liquid
Density 0.6548 g/mL
Melting point

−95 °C, 178 K, -139 °F

Boiling point

69 °C, 342 K, 156 °F

Solubility in water 13 mg/L at 20°C[1]
Viscosity 0.294 cP
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
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Hexane is a 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".

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

Isomers

Common name IUPAC name Text formula Skeletal formula
normal hexane
n-hexane
hexane CH3(CH2)4CH3 Hexane-2D-Skeletal.svg
isohexane 2-methylpentane (CH3)2CH(CH2)2CH3 2-metilpentāns.svg
3-methylpentane CH3CH2CH(CH3)CH2CH3 3-metilpentāns.svg
2,3-dimethylbutane CH3CH(CH3)CH(CH3)CH3 2,3-dimetilbutāns.svg
neohexane 2,2-dimethylbutane CH3C(CH3)2CH2CH3 2,2-dimetilbutāns.svg

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 from seeds, for cleansing and degreasing all sorts of items, and in textile manufacturing.

A typical laboratory use of hexanes is to extract oil and grease contaminants from water and soil for analysis.[3] 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, e.g. 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, and often replaced by n-heptane, which will not form the toxic (hexane-2,5-dione) metabolite.

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 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.[4]

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 temperature:[5]

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, and recently, plastic recyclers and assemblers and cleaners of capacitive touch-screen devices.[7]

In 1994, n-hexane was included in the list of chemicals on the US Toxic Release Inventory (TRI).[8] 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.[9]

Use in food processing

According to a report by the Cornucopia Institute, hexane is used to extract oil from grains as well as protein from soy, to such an extent that in 2007, grain processors were responsible for more than two-thirds of hexane emissions in the United States.[10] The report also pointed out that the hexane can persist in the final food product created; in a sample of processed soy, the oil contained 10 ppm, the meal 21 ppm and the grits 14 ppm hexane.[10] The adverse health effects seem specific to n-hexane; they are much reduced or absent for other isomers. Therefore, the food oil extraction industry, which relied heavily on hexane, has been considering switching to other solvents, including isohexane.[11][12][13]

Poisoning from touchscreen cleaner

In February 2010, reports surfaced saying that an employee of Wintek Corporation in China, a company that manufactures touchscreen components, died in August 2009 due to hexane poisoning. Hexane was used as a replacement for alcohol for cleaning the screens. Reports suggest up to 137 Chinese employees required treatment for hexane poisoning around the same time.[14][15][16] An ABC Foreign Correspondent episode covertly interviewed several women who had been in the hospital for over six months. The women claimed that they were exposed to hexane while manufacturing iPhone hardware.[17][18]

See also

References

  1. ^ n-Hexane, Date of Peer Review: April 2000
  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.
  4. ^ William D. McCain (1990), The properties of petroleum fluids. PennWell. ISBN 0-87814-335-1
  5. ^ vapor pressure
  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. ^ Dirty Secrets ABC News Broadcast: 26/10/2010
  8. ^ "N-Hexane Chemical Backgrounder". National Safety Council. Archived from the original on 19 May 2007. http://web.archive.org/web/20070519002303/http://www.nsc.org/ehc/chemical/N-Hexane.htm. Retrieved 25 May 2007. 
  9. ^ Anuradee Witthayapanyanon and Linh Do. "Nanostructured Microemulsions as Alternative Solvents to VOCs in Cleaning Technologies and Vegetable Oil Extraction". National Center For Environmental Research. Archived from the original on 13 October 2007. http://web.archive.org/web/20071013110614/http://es.epa.gov/ncer/publications/meetings/10_26_05/abstracts/do.html. Retrieved 25 May 2007. 
  10. ^ a b Cornucopia Institute (2009-05-18) Behind the Bean - The Heroes and Charlatans of the Natural and Organic Soy Foods Industry
  11. ^ Peter J. Wan, Phillip J. Wakelyn (1997), Technology and solvents for extracting oilseeds and nonpetroleum oils The American Oil Chemists Society. ISBN 0-935315-81-0, p. 189
  12. ^ USDA (1996), Isohexane—New Solvent for Cottonseed Oil Processing
  13. ^ Ono, Yuichiro; Takeuchi, Yasuhiro; Hisanaga, Naomi (1981). "A comparative study on the toxicity of n-hexane and its isomers on the peripheral nerve". International Archives of Occupational and Environmental Health 48 (3): 289–294. doi:10.1007/BF00405616. PMID 7251182. 
  14. ^ Worker Dies From N-hexane Poisoning At Touchscreen Factory Gizmodo, February 23, 2010
  15. ^ Silicon Sweatshops: Another black eye for Apple supplier Global Post, February 25, 2010
  16. ^ iPhone workers still sick after chemical poisoning IDG News Service February, 22 2011
  17. ^ Workers poisoned while making iPhones ABC News, October 25, 2010
  18. ^ Dirty Secrets ABC Foreign Correspondent, 2010-Oct-26

External links


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Look at other dictionaries:

  • Hexane — Formule brute et représentation 3D de l hexane …   Wikipédia en Français

  • hexane — ● hexane nom masculin Hydrocarbure saturé C6H14. hexane [ɛgzan] n. m. ÉTYM. 1903, in Rev. gén. des sc., no 1, p. 55; de hex , et ane. ❖ ♦ Chim. Hydrocarbure saturé (C6H14) combustible, faisant des mélanges explosifs avec l air …   Encyclopédie Universelle

  • Hexane — Hexane,   Singular Hexan das, s, zu den Alkanen zählende aliphatische Kohlenwasserstoffe mit der Summenformel C6H14, die in fünf Strukturisomeren vorkommen. Die Hexane sind farblose, leicht entzündliche Flüssigkeiten; sie sind (neben den… …   Universal-Lexikon

  • Hexane — Hex ane, n. [Gr. e x six.] (Chem.) Any one of five hydrocarbons, {C6H14}, of the paraffin series. They are colorless, volatile liquids, and are so called because the molecule has six carbon atoms. [1913 Webster] …   The Collaborative International Dictionary of English

  • Hexāne — Hexāne, Kohlenwasserstoffe von der Formel C6H14. Normales Hexan CH3.(CH2)4.CH3 ist der Hauptbestandteil des Petroleumäthers, findet sich auch im Teeröl der Boghead und der Kännelkohle, ist eine farblose Flüssigkeit vom spez. Gew. 0,663 und siedet …   Meyers Großes Konversations-Lexikon

  • hexane — paraffin hydrocarbon, 1872, from Gk. hex six (see SIX (Cf. six)) + chemical suffix ANE (Cf. ane). So called for its six carbon atoms …   Etymology dictionary

  • hexane — [hek′sān΄] n. [ HEX(A) + ANE] any of the five colorless, volatile, liquid isomeric alkanes, C6H14 …   English World dictionary

  • Hexane — Isomere Die Hexane sind in der Chemie eine Gruppe von aliphatischen, gesättigten Kohlenwasserstoffen bzw. Alkanen, die alle sechs Kohlenstoffatome im Molekül enthalten. Die Summenformel der Verbindungen ist C6H14. Es existieren fünf Isomere: n… …   Deutsch Wikipedia

  • hexane — A saturated hydrocarbon, C6H14, of the paraffin series (typically n h., CH3 (CH2)4 CH3). * * * hex·ane hek .sān n any of several isomeric volatile liquid alkanes C6H14 found in petroleum * * * hex·ane (hekґsān) n hexane; an aliphatic… …   Medical dictionary

  • hexane — heksanas statusas T sritis chemija formulė H(CH₂)₆H atitikmenys: angl. hexane rus. гексан …   Chemijos terminų aiškinamasis žodynas


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