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Higher alkanes are with a high number of carbon atoms. It is common jargon. One definition says higher alkanes are alkanes having nine or more carbon atoms. Thus, according to this definition, is the lightest higher alkane. As pure substances, higher alkanes are rarely significant, but they are major components of useful lubricants and fuels.


Synthesis
The preparation of specific long-chain hydrocarbons typically involves manipulations of long chain precursors or the coupling of two medium-chain components. For the first case, fatty acids can be a source of higher alkanes via reaction. Such processes have been investigated as a route to .

Fatty acid esters and fatty acid nitriles react with long chain to give, after suitable workup, long-chain ketones. The Wolff-Kishner Reaction provides a way to remove the functionality, giving long-chain hydrocarbons.

Even-numbered, long-chain hydrocarbons can also be synthesized through electrolysis and the of alkyl bromides.


Occurrence
Higher alkanes can also be isolated and purified from natural or synthetic mixtures. is a traditional source of mixtures of long-chain hydrocarbons.
(2025). 9783527306732
Careful fractionation, first using urea clathrates to remove branched hydrocarbons, and then distillation, produces pure n-hydrocarbons from petroleum.

Regarding synthetic sources, the Fischer-Tropsch process (or FT process) produces a mixture of hydrocarbons by the of . 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.


Bioactivity
Some branched higher alkanes are . 9- and 7-methyltricosanes are active for beetles (Adalia bipunctata). The emerald ash borer ( Agrilus planipennis Fairmaire) responds to 9-methylpentacosane. Female Asian long-horned beetles Anoplophora glabripennis, which are very damaging, secrete 2-methyl.


Reactions
Higher alkanes in general are relatively inert, just like low molecular weight alkanes they can react with oxygen and start a reaction. They can undergo cracking in the presence of alumina or silica , forming lower alkanes and alkenes.


Uses
Alkanes from to (those alkanes with nine to sixteen carbon atoms) are liquids of higher , which are less suitable for use in . They form instead the major part of , , and . Diesel fuels are characterised by their , 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 to flow correctly. Mixtures of the normal alkanes are used as standards for simulated by gas chromatography.

Alkanes from hexadecane upwards form the most important components of and . In latter function they work at the same time as anti-corrosive agents, as their nature means that water cannot reach the metal surface. Many solid alkanes find use as , used for , electrical insulation, and . Paraffin wax should not be confused with , which consists primarily of .

Alkanes with a chain length of approximately 30 or more carbon atoms are found in (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
  • cerane, for hexacosaneDonald Mackay, Handbook of Physical-Chemical Properties and Environmental Fate for Organic Chemicals, , p. 206


Properties
is the lightest alkane to have a above 25 °C, and is classified as under the US National Library of Medicine.

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.

C9H20C10H22C11H24C12H26C13H28C14H30C15H32C16H34
111-84-2124-18-51120-21-4112-40-3629-50-5629-59-4629-62-9544-76-3
(g/mol)128.26142.29156.31170.34184.37198.39212.42226.45
(°C)−53.5−29.7−25.6−9.6−5.45.99.918.2
(°C)150.8174.1195.9216.3235.4253.5270.6286.8
(g/ml at )0.717630.730050.740240.748690.756220.762750.768300.77344
(cP at )0.71390.92561.1851.5031.8802.3352.8633.474
(°C)314660717999132135
Autoignition temperature (°C)205210 205 235 201
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.

C17H36C18H38C19H40C20H42C21H44C22H46C23H48C24H50
629-78-7593-45-3629-92-5112-95-8629-94-7629-97-0638-67-5646-31-1
(g/mol)240.47254.50268.53282.55296.58310.61324.63338.66
(°C)2128–3032–3436.740.54248–5052
(°C)302317330342.7356.5224 at 2 kPaa380391.3
(g/ml)0.7770.7770.7860.78860.7920.7780.7970.797
(°C)148166168176
a


Pentacosane to triacontane
C25H52C26H54C27H56C28H58C29H60C30H62
629-99-2630-01-3593-49-7630-02-4630-03-5638-68-6
(g/mol)352.69366.71380.74394.77408.80422.82
(°C)5456.459.564.563.765.8
(°C)401412.2422431.6440.8449.7
(g/ml)0.8010.7780.7800.8070.8080.810


Hentriacontane to hexatriacontane
C31H64C32H66C33H68C34H70C35H72C36H74
630-04-6544-85-4630-05-714167-59-0630-07-9630-06-8
(g/mol)436.85450.88464.90478.93492.96506.98
(°C)67.96970–7272.67574–76
(°C)458467474285.4 at 0.4 kPa490265 at 130 Pa
(g/ml)0.781 at 68 °C0.8120.8110.8120.8130.814


Heptatriacontane to dotetracontane
C37H76C38H78C39H80C40H82C41H84C42H86
7194-84-57194-85-67194-86-74181-95-77194-87-87098-20-6
(g/mol)520.99535.03549.05563.08577.11591.13
(°C)777978848386
(°C)504.14510.93517.51523.88530.75536.07
(g/ml)0.8150.8160.8170.8170.8180.819


Tritetracontane to octatetracontane
C43H88C44H90C45H92C46H94C47H96C48H98
7098-21-77098-22-87098-23-97098-24-07098-25-17098-26-2
(g/mol)605.15619.18633.21647.23661.26675.29
(°C)541.91547.57553.1558.42563.6568.68
(g/ml)0.820.820.8210.8220.8220.823


Nonatetracontane to tetrapentacontane
C49H100C50H102C51H104C52H106C53H108C54H110
7098-27-36596-40-37667-76-77719-79-17719-80-45856-66-6
(g/mol)689.32703.34717.37731.39745.42759.45
(°C)573.6578.4583587.6592596.38
(g/ml)0.8230.8240.8240.8250.8250.826


Pentapentacontane to hexacontane
C55H112C56H114C57H116C58H118C59H120C60H122
5846-40-27719-82-65856-67-77667-78-97667-79-07667-80-3
(g/mol)773.48787.50801.53815.58829.59843.6
(°C)600.6604.7?612.6?620.2
(g/ml)0.8260.826?0.827?0.827


See also


External links

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