Higher alkane

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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 distinguishes the higher alkanes as the n-alkanes that are solid under room temperature.[ according to whom? ]

Contents

Synthesis

Higher alkanes are naturally present in crude oil and can be obtained via fractional distillation. Saturated fatty acids decarboxylate to higher alkanes. Long olefins can be hydrogenated to yield higher alkanes. n-alkanes can be isolated via the formation of urea clathrates.They can also be synthesized through Kolbe electrolysis or other coupling reactions like the Wurtz reaction.

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. [1]

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:

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. [3]

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. [4]

Nonane Decane Undecane Dodecane Tridecane Tetradecane Pentadecane Hexadecane
Formula C9H20C10H22C11H24C12H26C13H28C14H30C15H32C16H34
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)128.26142.29156.31170.34184.37198.39212.42226.45
Melting point (°C)53.529.725.69.65.45.99.918.2
Boiling point (°C)150.8174.1195.9216.3235.4253.5270.6286.8
Density (g/ml at 20 °C)0.717630.730050.740240.748690.756220.762750.768300.77344
Viscosity (cP at 20 °C)0.71390.92561.1851.5031.8802.3352.8633.474
Flash point (°C)314660717999132135
Autoignition
temperature
(°C)
205210205235201
Explosive limits 0.92.9%0.82.6%0.456.5%

Heptadecane to tetracosane

From this group on, the n-alkanes are generally solid at standard conditions.

Heptadecane Octadecane Nonadecane Icosane Heneicosane DocosaneTricosane Tetracosane
Formula C17H36C18H38C19H40C20H42C21H44C22H46C23H48C24H50
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)240.47254.50268.53282.55296.58310.61324.63338.66
Melting point (°C)212830323436.740.542485052
Boiling point (°C)302317330342.7356.5224 at 2 kPa380391.3
Density (g/ml)0.7770.7770.7860.78860.7920.7780.7970.797
Flash point (°C)148166168176

Pentacosane to triacontane

PentacosaneHexacosaneHeptacosaneOctacosane Nonacosane Triacontane
Formula C25H52C26H54C27H56C28H58C29H60C30H62
CAS number [629-99-2][630-01-3][593-49-7][630-02-4][630-03-5][638-68-6]
Molar mass (g/mol)352.69366.71380.74394.77408.80422.82
Melting point (°C)5456.459.564.563.765.8
Boiling point (°C)401412.2422431.6440.8449.7
Density (g/ml)0.8010.7780.7800.8070.8080.810

Hentriacontane to hexatriacontane

Hentriacontane DotriacontaneTritriacontaneTetratriacontanePentatriacontaneHexatriacontane
Formula C31H64C32H66C33H68C34H70C35H72C36H74
CAS number [630-04-6][544-85-4][630-05-7][14167-59-0][630-07-9][630-06-8]
Molar mass (g/mol)436.85450.88464.90478.93492.96506.98
Melting point (°C)67.969707272.6757476
Boiling point (°C)458467474285.4 at 0.4 kPa490265 at 130 Pa
Density (g/ml)0.781 at 68 °C [5] 0.8120.8110.8120.8130.814

Heptatriacontane to dotetracontane

HeptatriacontaneOctatriacontaneNonatriacontaneTetracontaneHentetracontaneDotetracontane
Formula C37H76C38H78C39H80C40H82C41H84C42H86
CAS number [7194-84-5][7194-85-6][7194-86-7][4181-95-7][7194-87-8][7098-20-6]
Molar mass (g/mol)520.99535.03549.05563.08577.11591.13
Melting point (°C)777978848386
Boiling point (°C)504.14510.93517.51523.88530.75536.07
Density (g/ml)0.8150.8160.8170.8170.8180.819

Tritetracontane to octatetracontane

TriatetracontaneTetratetracontanePentatetracontaneHexatetracontaneHeptatetracontaneOctatetracontane
Formula C43H88C44H90C45H92C46H94C47H96C48H98
CAS Number [7098-21-7][7098-22-8][7098-23-9][7098-24-0][7098-25-1][7098-26-2]
Molar mass (g/mol)605.15619.18633.21647.23661.26675.29
Boiling point (°C)541.91547.57553.1558.42563.6568.68
Density (g/ml)0.820.820.8210.8220.8220.823

Nonatetracontane to tetrapentacontane

NonatetracontanePentacontaneHenpentacontaneDopentacontaneTripentacontaneTetrapentacontane
Formula C49H100C50H102C51H104C52H106C53H108C54H110
CAS number [7098-27-3][6596-40-3][7667-76-7][7719-79-1][7719-80-4][5856-66-6]
Molar mass (g/mol)689.32703.34717.37731.39745.42759.45
Boiling point (°C)573.6578.4583587.6592596.38
Density (g/ml)0.8230.8240.8240.8250.8250.826

Pentapentacontane to hexacontane

PentapentacontaneHexapentacontaneHeptapentacontaneOctapentacontaneNonapentacontaneHexacontane
Formula C55H112C56H114C57H116C58H118C59H120C60H122
CAS number [5846-40-2][7719-82-6][5856-67-7][7667-78-9][7667-79-0][7667-80-3]
Molar mass (g/mol)773.48787.50801.53815.58829.59843.6
Boiling point (°C)600.6604.7 ?612.6 ?620.2
Density (g/ml)0.8260.826 ?0.827 ?0.827

See also

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References

  1. ASTM D5399-09, Standard Test Method for Boiling Point Distribution of Hydrocarbon Solvents by Gas Chromatography
  2. Donald Mackay, Handbook of Physical-Chemical Properties and Environmental Fate for Organic Chemicals, ISBN   1420044397, p. 206
  3. "Nonane". PubChem. 26 October 2024.
  4. 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
  5. Weast, Robert C., ed. (1982). CRC Handbook of Chemistry and Physics (63rd ed.). Boca Raton, Fl: CRC Press. p. C-561.