Hexane

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Hexane
Identifiers
CAS number110-54-3 YesY
PubChem8058
ChemSpider7767 YesY
UNII2DDG612ED8 YesY
EC number203-777-6
UN number1208
DrugBankDB02764
KEGGC11271 YesY
MeSHn-hexane
ChEBICHEBI:29021 YesY
ChEMBLCHEMBL15939 YesY
RTECS numberMN9275000
Beilstein Reference1730733
Gmelin Reference1985
Jmol-3D imagesImage 1
Properties
Molecular formulaC6H14
Molar mass86.18 g mol−1
AppearanceColorless liquid
OdorPetrolic
Density.6548 g mL−1
Melting point

-96--94 °C, 177-179 K, -141--137 °F

Boiling point

68-69 °C, 341.6-342.2 K, 155-156 °F

Solubility in water9.5 mg L−1
log P3.764
Vapor pressure17.60 kPa (at 20.0 °C)
kH7.6 nmol Pa−1 kg−1
λmax200 nm
Refractive index (nD)1.375
Viscosity294 μPa s
Thermochemistry
Std enthalpy of
formation
ΔfHo298
−199.4–−198.0 kJ mol−1
Std enthalpy of
combustion
ΔcHo298
−4180–−4140 kJ mol−1
Standard molar
entropy
So298
296.06 J K−1 mol−1
Specific heat capacity, C265.2 J K−1 mol−1
Hazards
MSDSExternal MSDS
GHS pictogramsThe flame pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) The exclamation-mark pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) The health hazard pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) The environment pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal wordDANGER
GHS hazard statementsH225, H304, H315, H336, H373, H411
GHS precautionary statementsP210, P261, P273, P281, P301+310, P331
EU Index601-037-00-0
EU classificationFlammable F Harmful Xn Dangerous for the Environment (Nature) N
R-phrasesR11, R38, R48/20, R51/53, R62, R65, R67
S-phrases(S2), S16, S29, S33, S36/37
NFPA 704
NFPA 704.svg
4
2
0
Flash point−26.0 °C
Autoignition
temperature
234.0 °C
Explosive limits1.2–7.7%
LD5025 g kg−1 (oral, rat)
Related compounds
Related alkanes
Supplementary data page
Structure and
properties
n, εr, etc.
Thermodynamic
data
Phase behaviour
Solid, liquid, gas
Spectral dataUV, 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
 
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Hexane
Identifiers
CAS number110-54-3 YesY
PubChem8058
ChemSpider7767 YesY
UNII2DDG612ED8 YesY
EC number203-777-6
UN number1208
DrugBankDB02764
KEGGC11271 YesY
MeSHn-hexane
ChEBICHEBI:29021 YesY
ChEMBLCHEMBL15939 YesY
RTECS numberMN9275000
Beilstein Reference1730733
Gmelin Reference1985
Jmol-3D imagesImage 1
Properties
Molecular formulaC6H14
Molar mass86.18 g mol−1
AppearanceColorless liquid
OdorPetrolic
Density.6548 g mL−1
Melting point

-96--94 °C, 177-179 K, -141--137 °F

Boiling point

68-69 °C, 341.6-342.2 K, 155-156 °F

Solubility in water9.5 mg L−1
log P3.764
Vapor pressure17.60 kPa (at 20.0 °C)
kH7.6 nmol Pa−1 kg−1
λmax200 nm
Refractive index (nD)1.375
Viscosity294 μPa s
Thermochemistry
Std enthalpy of
formation
ΔfHo298
−199.4–−198.0 kJ mol−1
Std enthalpy of
combustion
ΔcHo298
−4180–−4140 kJ mol−1
Standard molar
entropy
So298
296.06 J K−1 mol−1
Specific heat capacity, C265.2 J K−1 mol−1
Hazards
MSDSExternal MSDS
GHS pictogramsThe flame pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) The exclamation-mark pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) The health hazard pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) The environment pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal wordDANGER
GHS hazard statementsH225, H304, H315, H336, H373, H411
GHS precautionary statementsP210, P261, P273, P281, P301+310, P331
EU Index601-037-00-0
EU classificationFlammable F Harmful Xn Dangerous for the Environment (Nature) N
R-phrasesR11, R38, R48/20, R51/53, R62, R65, R67
S-phrases(S2), S16, S29, S33, S36/37
NFPA 704
NFPA 704.svg
4
2
0
Flash point−26.0 °C
Autoignition
temperature
234.0 °C
Explosive limits1.2–7.7%
LD5025 g kg−1 (oral, rat)
Related compounds
Related alkanes
Supplementary data page
Structure and
properties
n, εr, etc.
Thermodynamic
data
Phase behaviour
Solid, liquid, gas
Spectral dataUV, 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 /ˈhɛksn/ 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 nameIUPAC nameText formulaSkeletal formula
normal hexane
n-hexane
hexaneCH3(CH2)4CH3Hexane-2D-Skeletal.svg
isohexane2-methylpentane(CH3)2CH(CH2)2CH32-metilpentāns.svg
3-methylpentaneCH3CH2CH(CH3)CH2CH33-metilpentāns.svg
2,3-dimethylbutaneCH3CH(CH3)CH(CH3)CH32,3-dimetilbutāns.svg
neohexane2,2-dimethylbutaneCH3C(CH3)2CH2CH32,2-dimetilbutāns.svg

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 from seeds, for cleansing and degreasing a variety 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 metabolite hexane-2,5-dione.

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 colourless and odourless.[4][5] 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.[6]

IsomerM.P. (°C)B.P. (°C)
n-hexane−95.368.7
3-methylpentane−118.063.3
2-methylpentane (isohexane)−153.760.3
2,3-dimethylbutane−128.658.0
2,2-dimethylbutane (neohexane)−99.849.7

Normal hexane has considerable vapor pressure at room temperature:[7]

Temperature (°C)Vapor pressure (mmHg)
−403.36
−307.12
−2014.01
−1025.91
045.37
1075.74
20121.26
25151.28
30187.11
40279.42
50405.31
60572.76

Toxicity[edit]

The acute toxicity of n-hexane is 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 toxicity of n-hexane has been extensively discussed by the Agency for Toxic Substances and Disease Registry.[8]

The long-term toxicity of n-hexane in humans is well known.[9] 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.[10]

In 1994, n-hexane was included in the list of chemicals on the US Toxic Release Inventory (TRI).[11] 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.[12]

Use in food processing[edit]

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.[13] 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.[13] 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 (2-methylpentane).[14][15][16]

Poisoning from touchscreen cleaner[edit]

In February 2010, reports surfaced saying that an employee of Wintek Corporation, an Apple contractor in China, a company that manufactures iPhone 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.[17][18][19] An ABC Foreign Correspondent episode covertly interviewed several women who had been in the hospital for over six months. The women said that they were exposed to hexane while manufacturing iPhone hardware.[20][21] Apple has since required Wintek and other suppliers to cease using hexane.[22]

See also[edit]

References[edit]

  1. ^ "n-hexane – Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 16 September 2004. Identification and Related Records. Retrieved 31 December 2011. 
  2. ^ "C5 and C6 alkanes". A and B Scott Organic Chemistry. Retrieved 30 October 2007. 
  3. ^ Use of ozone depleting substances in laboratories. TemaNord 2003:516.
  4. ^ http://nsdl.niscair.res.in/bitstream/123456789/777/1/Revised+organic+chemistry.pdf
  5. ^ http://textbook.s-anand.net/ncert/class-11/chemistry/13-hydrocarbons
  6. ^ William D. McCain (1990), The properties of petroleum fluids. PennWell. ISBN 0-87814-335-1
  7. ^ vapor pressure
  8. ^ Agency for Toxic Substances and Disease Registry (July 1999). "Toxicological Profile For n-Hexane". Atlanta, GA: U.S. Department Of Health And Human Services. p. 269. Retrieved 2012-06-22. 
  9. ^ Hathaway GJ, Proctor NH, Hughes JP, and Fischman M (2004). Proctor and Hughes' chemical hazards of the workplace. Wiley-Interscience,. ISBN 0-471-26883-6. 
  10. ^ Dirty Secrets ABC News Broadcast: 26/10/2010
  11. ^ "N-Hexane Chemical Backgrounder". National Safety Council. Archived from the original on 19 May 2007. Retrieved 25 May 2007. 
  12. ^ 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. Retrieved 25 May 2007. 
  13. ^ a b Cornucopia Institute (2009-05-18) Behind the Bean – The Heroes and Charlatans of the Natural and Organic Soy Foods Industry
  14. ^ 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
  15. ^ USDA (1996), Isohexane—New Solvent for Cottonseed Oil Processing
  16. ^ 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. 
  17. ^ Worker Dies From N-hexane Poisoning At Touchscreen Factory Gizmodo, 23 February 2010
  18. ^ Silicon Sweatshops: Another black eye for Apple supplier Global Post, 25 February 2010
  19. ^ iPhone workers still sick after chemical poisoning IDG News Service February 22, 2011
  20. ^ Workers poisoned while making iPhones ABC News, 25 October 2010
  21. ^ Dirty Secrets ABC Foreign Correspondent, 2010-Oct-26
  22. ^ [1] Apple Supplier Responsibility

External links[edit]