Hexane

from Wikipedia, the free encyclopedia
Structural formula
Structure of hexane
General
Surname Hexane
other names

n -hexane

Molecular formula C 6 H 14
Brief description

colorless liquid with a weak gasoline smell

External identifiers / databases
CAS number 110-54-3
EC number 203-777-6
ECHA InfoCard 100.003.435
PubChem 8058
Wikidata Q150440
properties
Molar mass 86.18 g mol −1
Physical state

liquid

density

0.66 g cm −3

Melting point

−95 ° C

boiling point

69 ° C

Vapor pressure

162 h Pa (20 ° C)

solubility
Refractive index

1.3727 (20 ° C)

safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary
02 - Highly / extremely flammable 08 - Dangerous to health 07 - Warning 09 - Dangerous for the environment

danger

H and P phrases H: 225-304-361f-373-315-336-411
P: 210-240-273-301 + 310-331-302 + 352-403 + 235
MAK

DFG / Switzerland: 50 ml m −3 or 180 mg m −3

Toxicological data

25,000 mg kg −1 ( LD 50 ,  rat ,  oral )

As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C

Hexane is a chemical compound belonging to alkanes (saturated hydrocarbons ) . It is a colorless liquid with the empirical formula C 6 H 14 . It is the unbranched isomer of the five hexane isomers .

properties

Hexane is a colorless, volatile liquid that smells slightly like gasoline . The boiling point under normal pressure is 68.8 ° C. The compound melts at −95.4 ° C. The relative dielectric constant is 1.8 at 20 ° C. It is practically insoluble in water. It is readily soluble in organic solvents such as alcohols (with the exception of methanol ), ethers and benzene .

The compound forms azeotropically boiling mixtures with a number of other solvents . The azeotropic compositions and boiling points can be found in the following table. No azeotropes are formed with cyclohexane , n- pentane , heptane , octane , toluene , ethylbenzene , xylene , cyclohexanol and diethyl ether .

Azeotropes with various solvents (according to Smallwood)
solvent water Methanol Ethanol 1-propanol 2-propanol
Content of hexane in% 94 72 79 96 77
boiling point in ° C 62 50 59 66 63
solvent 1-butanol i-butanol 2-butanol Ethylene glycol ethyl ether Acetonitrile
Content of hexane in% 97 98 92 95 72
boiling point in ° C 68 68 67 66 52
solvent chloroform acetic acid acetone Methyl ethyl ketone Diisopropyl ether
Content of hexane in% 16 95 41 71 47
boiling point in ° C 60 68 50 64 67
solvent Dioxane THF Methyl acetate Ethyl acetate Isopropyl acetate
Content of hexane in% 98 50 39 62 91
boiling point in ° C 60 63 52 65 69

Thermodynamic properties

According to Antoine, the vapor pressure function results from log 10 (P) = A− (B / (T + C)) (P in bar, T in K) with A = 3.45604, B = 1044.038 and C = −53.893 in the temperature range from 177.70 to 264.93 K or with A = 4.00266, B = 1171.530 and C = −48.784 in the temperature range from 286.18 to 342.69 K.

Compilation of the most important thermodynamic properties
property Type Value [unit] Remarks
Standard enthalpy of formation Δ f H 0 liquid
Δ f H 0 gas 		−198.7 kJ mol −1
−167.1 kJ mol −1 		as a liquid
as a gas
Standard entropy S 0 liquid
S 0 gas 		296.06 J mol −1 K −1
388.82 J mol −1 K −1 		as a liquid
as a gas
Enthalpy of combustion Δ c H 0 liquid −4163.2 kJ mol −1
Heat capacity c p 194.97 J mol −1 K −1 (25 ° C)
2.30 J g −1 K −1 (25 ° C)
142.6 J mol −1 K −1 (25 ° C )
1.65 J g −1 K −1 (25 ° C) 		as a liquid

as a gas
Critical temperature T c 507.5 K
Critical pressure p c 29.9 bar
Critical volume V c 0.368 l mol −1
Critical density ρ c 2.72 mol·l −1
Acentric factor ω c 0.30126
Enthalpy of fusion Δ f H 0 13.08 kJ mol −1 at the melting point
Enthalpy of evaporation Δ V H 0
Δ V H 		31.73 kJ mol −1
28.85 kJ mol −1
at normal pressure boiling point

The temperature dependence of the enthalpy of evaporation can be calculated according to the equation Δ V H 0 = Aexp (−αT r ) (1 − T r ) β (Δ V H 0 in kJ / mol, T r = (T / T c ) reduced temperature) with Describe A = 43.85 kJ / mol, α = −0.039, β = 0.397 and T c = 507.4 K in the temperature range between 298 K and 444 K.

Safety-related parameters

n- hexane forms highly flammable vapor-air mixtures. The compound has a flash point of −20 ° C. The explosion range is between 1% by volume (35 g / m 3 ) as the lower explosion limit (LEL) and 8.9% by volume (319 g / m 3 ) as the upper explosion limit (UEL). A correlation of the explosion limits with the vapor pressure function results in a lower explosion point of −28 ° C and an upper explosion point of 7 ° C. The explosion limits are pressure dependent. A decrease in pressure leads to a reduction in the explosion area. The lower explosion limit changes only slightly up to a pressure of 100 mbar and only increases at pressures below 100 mbar. The upper explosion limit decreases analogously with falling pressure.

Explosion limits under reduced pressure (measured at 100 ° C)
pressure in mbar 1013 800 600 400 300 250 200 150 100 50 25th
Lower explosion limit (LEL) in% by volume 0.9 0.9 0.9 0.9 1.0 1.0 1.0 1.1 1.2 1.6 3.5
in g m −3 30th 31 32 33 34 35 37 39 43 58 125
Upper explosion limit (UEL) in% by volume 8.9 8.7 8.3 7.8 7.6 7.5 7.4 7.3 7.2 6.0 4.7
in g m −3 319 312 297 279 272 269 265 262 258 215 168

The lower explosion limit decreases with increasing temperature. The linear function LEL (T) = LEL (T 0 ) · [1 + k u (TT 0 )] (with T 0 = 20 ° C) results in a temperature coefficient k u of −0.0027 K −1 .

Lower explosion limits with increasing temperature
temperature in ° C 20th 100 150 200 250
Lower explosion limit (LEL) in% by volume 1.0 0.9 0.6 0.5 0.4

The limit oxygen concentration at 20 ° C is 9.1% by volume, at 100 ° C it is 8.3% by volume. The value tends to increase with decreasing pressure and decrease with increasing temperature. The maximum explosion pressure is 9.5 bar. The maximum explosion pressure decreases as the outlet pressure decreases.

Maximum explosion pressure and limit oxygen concentration under reduced pressure
pressure in mbar 1013 800 600 400 300 200 150 100
Maximum explosion pressure in cash at 20 ° C 9.6 7.4 5.6 3.7 2.8 1.8 1.4 1.1
Limit oxygen concentration in vol% at 20 ° C 9.1 9.5 10.1 10.8
at 100 ° C 8.3 8.3 8.8

With a minimum ignition energy of 0.24 mJ, vapor-air mixtures are extremely ignitable. The limit gap width was determined to be 0.93 mm. This results in an assignment to explosion group IIA. The ignition temperature is 230 ° C. The substance therefore falls into temperature class T3.

use

Hexane in an Erlenmeyer flask

Hexane is used in organic chemistry as a solvent and reaction medium in polymerizations , as a diluent for fast-drying paints, printing inks and adhesives and as an elution and solvent in thin-layer chromatography . It is still used to manufacture plastics and synthetic rubber, as well as for oil and fat extraction . Since it does not attack polystyrene , unlike many organic solvents, and is highly volatile, it is used as a solvent for styrofoam glue .

Safety instructions / toxicology

Hexane is addictive and harmful to health. Hexane is hazardous to water ( WGK 2). Hexane is metabolized in the body to 2,5-hexanedione , this leads to nerve damage and is excreted in the urine. Because of this harmful effect, n-hexane is increasingly being replaced by n-heptane

In 2012, hexane was included in the EU's ongoing action plan ( CoRAP ) in accordance with Regulation (EC) No. 1907/2006 (REACH) as part of substance evaluation . The effects of the substance on human health and the environment are re-evaluated and, if necessary, follow-up measures are initiated. Hexane uptake was caused by concerns about its classification as a CMR substance, high (aggregated) tonnage, other hazard-related concerns and widespread use. The reassessment took place from 2012 and was carried out by Germany . A final report was then published.

Web links

Commons : Hexane  - collection of pictures, videos and audio files
Wiktionary: Hexane  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ↑ a b Data sheet n-hexane (PDF) from Merck , accessed on February 15, 2010.
  2. ↑ a b c d e f g h i Entry on hexane in the GESTIS substance database of the IFA , accessed on February 1, 2016(JavaScript required) .
  3. ↑ a b Entry on hexane. In: Römpp Online . Georg Thieme Verlag, accessed on December 9, 2014.
  4. ↑ Entry on N-hexane in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
  5. ↑ Swiss Accident Insurance Fund (Suva): Limit values ​​- current MAK and BAT values (search for 110-54-3 or n-hexane ), accessed on November 2, 2015.
  6. ↑ L.-C. Feng, C.-H. Chou, M. Tang, YP Chen: Vapor-Liquid Equilibria of Binary Mixtures 2-Butanol + Butyl Acetate, Hexane + Butyl Acetate, and Cyclohexane + 2-Butanol at 101.3 kPa. In: J. Chem. Eng. Data . 43, 1998, pp. 658-661, doi: 10.1021 / je9800205 .
  7. ^ A b G. F. Carruth, R. Kobayashi: Vapor Pressure of Normal Paraffins Ethane Through n-Decane from Their Triple Points to About 10 Mm mercury. In: J. Chem. Eng. Data. 18, 1973, pp. 115-126, doi: 10.1021 / je60057a009 .
  8. ^ IM Smallwood: Handbook of Organic Solvent Properties. Arnold, London 1996, ISBN 0-340-64578-4 , pp. 12-13.
  9. ↑ CB Williamham, WJ Taylor, JM Pignocco, FD Rossini: Vapor Pressures and Boiling Points of Some Paraffin, Alkylcyclopentane, Alkylcyclohexane, and Alkylbenzene Hydrocarbons. In: J. Res. Natl. Bur. Stand. (US). 35, 1945, pp. 219-244.
  10. ↑ a b c W. D. Good, NK Smith: Enthalpies of combustion of toluene, benzene, cyclohexane, cyclohexene, methylcyclopentane, 1-methylcyclopentene, and n-hexane. In: J. Chem. Eng. Data . 14, 1969, pp. 102-106, doi: 10.1021 / je60040a036 .
  11. ↑ a b c D. R. Douslin, HM Huffman: Low-temperature thermal data on the five isometric hexanes. In: J. Am. Chem. Soc. 68, 1946, pp. 1704-1708, doi: 10.1021 / ja01213a006 .
  12. ^ DW Scott: Correlation of the chemical thermodynamic properties of alkane hydrocarbons. In: J. Chem. Phys. 60, 1974, pp. 3144-3165, doi: 10.1063 / 1.1681500 .
  13. ^ A b D. W. Scott: Chemical Thermodynamic Properties of Hydrocarbons and Related Substances. Properties of the Alkane Hydrocarbons, C1 through C10 in the Ideal Gas State from 0 to 1500 K. In: US Bureau of Mines, Bulletin. 666, 1974.
  14. ↑ a b S. K. Quadri, KC Khilar, AP Kudchadker, MJ Patni: Measurement of the critical temperatures and critical pressures of some thermally stable or mildly unstable alkanols. In: J. Chem. Thermodyn. 23, 1991, pp. 67-76, doi: 10.1016 / S0021-9614 (05) 80060-6 .
  15. ^ A b D. Ambrose, C. Tsonopoulos: Vapor-Liquid Critical Properties of Elements and Compounds. 2. Normal Alkenes. In: J. Chem. Eng. Data. 40, 1995, pp. 531-546, doi: 10.1021 / je00019a001 .
  16. ↑ J. Schmidt: Design of safety valves for multi-purpose systems according to ISO 4126-10. In: Chem. Ing. Techn. 83, 2011, pp. 796-812, doi: 10.1002 / cite.201000202 .
  17. ↑ ES Domalski, ED Hearing: Heat Capacities and Entropies of Organic Compounds in the Condensed phase. Volume III. In: J. Phys. Chem. Ref. Data . 25, 1996, pp. 1-525, doi: 10.1063 / 1.555985 .
  18. ^ A b c V. Majer, V. Svoboda: Enthalpies of Vaporization of Organic Compounds: A Critical Review and Data Compilation. Blackwell Scientific Publications, Oxford 1985, p. 300.
  19. ↑ a b c d e f E. Brandes, W. Möller: Safety-related parameters. Volume 1: Flammable Liquids and Gases. Wirtschaftsverlag NW - Verlag für neue Wissenschaft, Bremerhaven 2003.
  20. ↑ a b c d e f D. Pawel, E. Brandes: Final report on the research project, the dependence of safety parameters on the pressure below atmospheric pressure. ( Memento of December 2, 2013 in the Internet Archive ), Physikalisch-Technische Bundesanstalt (PTB), Braunschweig 1998.
  21. ↑ a b W. Hirsch, E. Brandes: Final report of the research project parameters under non-atmospheric conditions. Physikalisch-Technische Bundesanstalt (PTB), Braunschweig 2014. (PDF file)
  22. ↑ Hexane (n ‐ Hexane) MAK Value Documentation in German language, 1997 , accessed on October 15, 2019.
  23. ↑ European Chemicals Agency (ECHA): Substance Evaluation Conclusion and Evaluation Report .
  24. ↑ Community rolling action plan ( CoRAP ) of the European Chemicals Agency (ECHA): n-hexane , accessed on March 26, 2019.