Hexane
Structural formula | ||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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 | ||||||||||||||||
|
||||||||||||||||
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 | ||||||||||||||||
|
||||||||||||||||
MAK |
DFG / Switzerland: 50 ml m −3 or 180 mg m −3 |
|||||||||||||||
Toxicological data | ||||||||||||||||
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.
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.
Vapor pressure function of hexane
Temperature dependence of the heat of vaporization of hexane
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 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
Individual evidence
- ↑ a b Data sheet n-hexane (PDF) from Merck , accessed on February 15, 2010.
- ↑ 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) .
- ↑ a b Entry on hexane. In: Römpp Online . Georg Thieme Verlag, accessed on December 9, 2014.
- ↑ 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 .
- ↑ 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.
- ↑ 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 .
- ^ 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 .
- ^ IM Smallwood: Handbook of Organic Solvent Properties. Arnold, London 1996, ISBN 0-340-64578-4 , pp. 12-13.
- ↑ 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.
- ↑ 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 .
- ↑ 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 .
- ^ 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 .
- ^ 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.
- ↑ 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 .
- ^ 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 .
- ↑ 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 .
- ↑ 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 .
- ^ 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.
- ↑ 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.
- ↑ 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.
- ↑ 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)
- ↑ Hexane (n ‐ Hexane) MAK Value Documentation in German language, 1997 , accessed on October 15, 2019.
- ↑ European Chemicals Agency (ECHA): Substance Evaluation Conclusion and Evaluation Report .
- ↑ Community rolling action plan ( CoRAP ) of the European Chemicals Agency (ECHA): n-hexane , accessed on March 26, 2019.