Higher alkane
Higher alkanes refer to alkanes with a high number of carbon atoms. There does not exist a formal definition for when an alkane is classified as a 'higher alkane', but one definition says higher alkanes are alkanes having nine or more carbon atoms. Thus, according to this definition, nonane is the lightest higher alkane.[1]
Synthesis
Higher alkanes can be produced in several ways, they are naturally present in crude oil and can be obtained via fractional distillation. Similar to low molecular weight alkanes, there are several ways to synthesize higher alkanes:
Decarboxylation of fatty acids
Synthesis from saturated fatty acids decarboxylation leads to the formation of higher alkanes, as fatty acids chain length is usually between C10 and C22.[2]
Fischer-Tropsch process
Fischer-Tropsch process (or FT process) consist of the reaction of syngas: a mixture of hydrogen and carbon monoxide. The reaction is carried out at temperatures of 200°C-350°C at pressures of 20 Bar-50 Bar in the presence of a metal catalyst (iron or cobalt). The products obtained are liquid hydrocarbons and waxy solids, mostly n-paraffins. The liquid fraction ranges from C6 to C20, while the solid fraction consists of hydrocarbons above C21.[3][4]
Hydrogenation of long chain olefins
Long alkenes (olefins) possess at least one double bond. Being quite reactive, it can easily break under the right conditions. Using hydrogen in the presence of a metal catalyst, such as platinum, palladium or nickel, the long alkene can undergo an addition reaction, forming long alkanes as products.[5]
Urea extraction crystallization
n-alkanes can be isolated via the formation of urea clathrates.
Kolbe electrolysis
They can also be synthesized through Kolbe electrolysis
Wurtz reaction
They can be synthesized via Wurtz reaction.
Reactions
Higher alkanes in general are relatively inert, just like low molecular weight alkanes they can react with oxygen and start a combustion reaction. They can undergo pyrolisis in the presence of alumina or silica catalysts, forming lower alkanes and alkenes.[6] They undergo halogenation with chlorine when irradiated with ultraviolet light.[7]
Uses
Alkanes from nonane to hexadecane (those alkanes with nine to sixteen carbon atoms) are liquids of higher viscosity, which are less suitable for use in gasoline. They form instead the major part of diesel, kerosene, and aviation fuel. Diesel fuels are characterised by their cetane number, cetane being an older name for hexadecane. However the higher melting points of these alkanes can cause problems at low temperatures and in polar regions, where the fuel becomes too thick to flow correctly. Mixtures of the normal alkanes are used as boiling point standards for simulated distillation by gas chromatography.[8]
Alkanes from hexadecane upwards form the most important components of fuel oil and lubricating oil. In latter function they work at the same time as anti-corrosive agents, as their hydrophobic nature means that water cannot reach the metal surface. Many solid alkanes find use as paraffin wax, used for lubrication, electrical insulation, and candles. Paraffin wax should not be confused with beeswax, which consists primarily of esters.
Alkanes with a chain length of approximately 35 or more carbon atoms are found in bitumen (asphalt), used (for example) in road surfacing. However, the higher alkanes have little value and are usually split into lower alkanes by cracking.
Names
Some alkanes have non-IUPAC trivial names:
- cetane, for hexadecane
- cerane, for hexacosane[9]
Properties
Nonane is the lightest alkane to have a flash point above 25 °C, and is classified as flammable under the US National Library of Medicine. [10]
The properties listed here refer to the straight-chain alkanes (or: n-alkanes).
Nonane to hexadecane
This group of n-alkanes is generally liquid under standard conditions.[11]
Nonane | Decane | Undecane | Dodecane | Tridecane | Tetradecane | Pentadecane | Hexadecane | |
---|---|---|---|---|---|---|---|---|
Formula | C9H20 | C10H22 | C11H24 | C12H26 | C13H28 | C14H30 | C15H32 | C16H34 |
CAS number | [111-84-2] | [124-18-5] | [1120-21-4] | [112-40-3] | [629-50-5] | [629-59-4] | [629-62-9] | [544-76-3] |
Molar mass (g/mol) | 128.26 | 142.29 | 156.31 | 170.34 | 184.37 | 198.39 | 212.42 | 226.45 |
Melting point (°C) | −53.5 | −29.7 | −25.6 | −9.6 | −5.4 | 5.9 | 9.9 | 18.2 |
Boiling point (°C) | 150.8 | 174.1 | 195.9 | 216.3 | 235.4 | 253.5 | 270.6 | 286.8 |
Density (g/ml at 20 °C) | 0.71763 | 0.73005 | 0.74024 | 0.74869 | 0.75622 | 0.76275 | 0.76830 | 0.77344 |
Viscosity (cP at 20 °C) | 0.7139 | 0.9256 | 1.185 | 1.503 | 1.880 | 2.335 | 2.863 | 3.474 |
Flash point (°C) | 31 | 46 | 60 | 71 | 79 | 99 | 132 | 135 |
Autoignition temperature (°C) |
205 | 210 | 205 | 235 | 201 | |||
Explosive limits | 0.9–2.9% | 0.8–2.6% | 0.45–6.5% |
Heptadecane to tetracosane
From this group on, the n-alkanes are generally solid at standard conditions.
Heptadecane | Octadecane | Nonadecane | Icosane | Heneicosane | Docosane | Tricosane | Tetracosane | |
---|---|---|---|---|---|---|---|---|
Formula | C17H36 | C18H38 | C19H40 | C20H42 | C21H44 | C22H46 | C23H48 | C24H50 |
CAS number | [629-78-7] | [593-45-3] | [629-92-5] | [112-95-8] | [629-94-7] | [629-97-0] | [638-67-5] | [646-31-1] |
Molar mass (g/mol) | 240.47 | 254.50 | 268.53 | 282.55 | 296.58 | 310.61 | 324.63 | 338.66 |
Melting point (°C) | 21 | 28–30 | 32–34 | 36.7 | 40.5 | 42 | 48–50 | 52 |
Boiling point (°C) | 302 | 317 | 330 | 342.7 | 356.5 | 224 at 2 kPa | 380 | 391.3 |
Density (g/ml) | 0.777 | 0.777 | 0.786 | 0.7886 | 0.792 | 0.778 | 0.797 | 0.797 |
Flash point (°C) | 148 | 166 | 168 | 176 |
Pentacosane to triacontane
Pentacosane | Hexacosane | Heptacosane | Octacosane | Nonacosane | Triacontane | |
---|---|---|---|---|---|---|
Formula | C25H52 | C26H54 | C27H56 | C28H58 | C29H60 | C30H62 |
CAS number | [629-99-2] | [630-01-3] | [593-49-7] | [630-02-4] | [630-03-5] | [638-68-6] |
Molar mass (g/mol) | 352.69 | 366.71 | 380.74 | 394.77 | 408.80 | 422.82 |
Melting point (°C) | 54 | 56.4 | 59.5 | 64.5 | 63.7 | 65.8 |
Boiling point (°C) | 401 | 412.2 | 422 | 431.6 | 440.8 | 449.7 |
Density (g/ml) | 0.801 | 0.778 | 0.780 | 0.807 | 0.808 | 0.810 |
Hentriacontane to hexatriacontane
Hentriacontane | Dotriacontane | Tritriacontane | Tetratriacontane | Pentatriacontane | Hexatriacontane | |
---|---|---|---|---|---|---|
Formula | C31H64 | C32H66 | C33H68 | C34H70 | C35H72 | C36H74 |
CAS number | [630-04-6] | [544-85-4] | [630-05-7] | [14167-59-0] | [630-07-9] | [630-06-8] |
Molar mass (g/mol) | 436.85 | 450.88 | 464.90 | 478.93 | 492.96 | 506.98 |
Melting point (°C) | 67.9 | 69 | 70–72 | 72.6 | 75 | 74–76 |
Boiling point (°C) | 458 | 467 | 474 | 285.4 at 0.4 kPa | 490 | 265 at 130 Pa |
Density (g/ml) | 0.781 at 68 °C[12] | 0.812 | 0.811 | 0.812 | 0.813 | 0.814 |
Heptatriacontane to dotetracontane
Heptatriacontane | Octatriacontane | Nonatriacontane | Tetracontane | Hentetracontane | Dotetracontane | |
---|---|---|---|---|---|---|
Formula | C37H76 | C38H78 | C39H80 | C40H82 | C41H84 | C42H86 |
CAS number | [7194-84-5] | [7194-85-6] | [7194-86-7] | [4181-95-7] | [7194-87-8] | [7098-20-6] |
Molar mass (g/mol) | 520.99 | 535.03 | 549.05 | 563.08 | 577.11 | 591.13 |
Melting point (°C) | 77 | 79 | 78 | 84 | 83 | 86 |
Boiling point (°C) | 504.14 | 510.93 | 517.51 | 523.88 | 530.75 | 536.07 |
Density (g/ml) | 0.815 | 0.816 | 0.817 | 0.817 | 0.818 | 0.819 |
Tritetracontane to octatetracontane
Triatetracontane | Tetratetracontane | Pentatetracontane | Hexatetracontane | Heptatetracontane | Octatetracontane | |
---|---|---|---|---|---|---|
Formula | C43H88 | C44H90 | C45H92 | C46H94 | C47H96 | C48H98 |
CAS Number | [7098-21-7] | [7098-22-8] | [7098-23-9] | [7098-24-0] | [7098-25-1] | [7098-26-2] |
Molar mass (g/mol) | 605.15 | 619.18 | 633.21 | 647.23 | 661.26 | 675.29 |
Boiling point (°C) | 541.91 | 547.57 | 553.1 | 558.42 | 563.6 | 568.68 |
Density (g/ml) | 0.82 | 0.82 | 0.821 | 0.822 | 0.822 | 0.823 |
Nonatetracontane to tetrapentacontane
Nonatetracontane | Pentacontane | Henpentacontane | Dopentacontane | Tripentacontane | Tetrapentacontane | |
---|---|---|---|---|---|---|
Formula | C49H100 | C50H102 | C51H104 | C52H106 | C53H108 | C54H110 |
CAS number | [7098-27-3] | [6596-40-3] | [7667-76-7] | [7719-79-1] | [7719-80-4] | [5856-66-6] |
Molar mass (g/mol) | 689.32 | 703.34 | 717.37 | 731.39 | 745.42 | 759.45 |
Boiling point (°C) | 573.6 | 578.4 | 583 | 587.6 | 592 | 596.38 |
Density (g/ml) | 0.823 | 0.824 | 0.824 | 0.825 | 0.825 | 0.826 |
Pentapentacontane to hexacontane
Pentapentacontane | Hexapentacontane | Heptapentacontane | Octapentacontane | Nonapentacontane | Hexacontane | |
---|---|---|---|---|---|---|
Formula | C55H112 | C56H114 | C57H116 | C58H118 | C59H120 | C60H122 |
CAS number | [5846-40-2] | [7719-82-6] | [5856-67-7] | [7667-78-9] | [7667-79-0] | [7667-80-3] |
Molar mass (g/mol) | 773.48 | 787.50 | 801.53 | 815.58 | 829.59 | 843.6 |
Boiling point (°C) | 600.6 | 604.7 | ? | 612.6 | ? | 620.2 |
Density (g/ml) | 0.826 | 0.826 | ? | 0.827 | ? | 0.827 |
See also
- Alkene
- Alkyne
- Cycloalkane
- Hydrocarbon
- Paraffin wax, composed mostly of higher linear alkanes
- Polyethylene, a linear alkane of polymeric length
References
- ^ "Higher alkanes". Wartsila.com. Retrieved 2025-05-06.
- ^ "Fatty Acids - an overview". www.sciencedirect.com. Retrieved 2025-05-06.
- ^ "Fischer-Tropsch Process". www.sciencedirect.com. Retrieved 2025-05-06.
- ^ "Fischer-Tropsch products from biomass-derived syngas and renewable hydrogen". Retrieved 2025-05-06.
- ^ "Catalytic Hydrogenation of Alkenes". Chemistry LibreTexts. 2013-10-02. Retrieved 2025-05-06.
- ^ "ALKANES AND THEIR PREPARATION" (PDF). Retrieved 2025-05-06.
- ^ "Properties of Alkanes". Retrieved 2025-05-06.
- ^ ASTM D5399-09, Standard Test Method for Boiling Point Distribution of Hydrocarbon Solvents by Gas Chromatography
- ^ Donald Mackay, Handbook of Physical-Chemical Properties and Environmental Fate for Organic Chemicals, ISBN 1420044397, p. 206
- ^ "Nonane". PubChem. 26 October 2024.
- ^ Karl Griesbaum, Arno Behr, Dieter Biedenkapp, Heinz-Werner Voges, Dorothea Garbe, Christian Paetz, Gerd Collin, Dieter Mayer Hartmut Höke "Hydrocarbons" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. doi:10.1002/14356007.a13_227
- ^ Weast, Robert C., ed. (1982). CRC Handbook of Chemistry and Physics (63rd ed.). Boca Raton, Fl: CRC Press. p. C-561.
External links
- International Chemical Safety Card 1245 (nonane)
- NIOSH Pocket Guide to Chemical Hazards (nonane)
- International Chemical Safety Card 0428 (decane)