Higher alkanes


Higher alkanes are alkanes having nine or more carbon atoms. Nonane is the lightest alkane to have a flash point above 25 °C, and is not classified as dangerously flammable.
The term higher alkanes is sometimes used literally as "alkanes with a higher number of carbon atoms". One definition distinguishes the higher alkanes as the n-alkanes that are solid under natural conditions.

Uses

Alkanes from nonane to hexadecane are liquids of higher viscosity, which are less suitable for use in gasoline. They form instead the major part of diesel 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.
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, used 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:
The properties listed here refer to the straight-chain alkanes.

Nonane to hexadecane

This group of n-alkanes is generally liquid under standard conditions.
NonaneDecaneUndecaneDodecaneTridecaneTetradecanePentadecaneHexadecane
FormulaC9H20C10H22C11H24C12H26C13H28C14H30C15H32C16H34
CAS number
Molar mass 128.26142.29156.31170.34184.37198.39212.42226.45
Melting point −53.5−29.7−25.6−9.6−5.45.99.918.2
Boiling point 150.8174.1195.9216.3235.4253.5270.6286.8
Density 0.717630.730050.740240.748690.756220.762750.768300.77344
Viscosity 0.71390.92561.1851.5031.8802.3352.8633.474
Flash point 314660717999132135
Autoignition
temperature 		205210205235201
Explosive limits0.9-2.9%0.8-2.6%0.45-6.5%

Heptadecane to tetracosane

From this group on, the n-alkanes are generally solid at standard conditions.
HeptadecaneOctadecaneNonadecaneIcosaneHeneicosaneDocosaneTricosaneTetracosane
FormulaC17H36C18H38C19H40C20H42C21H44C22H46C23H48C24H50
CAS number
Molar mass 240.47254.50268.53282.55296.58310.61324.63338.66
Melting point 2128-3032-3436.740.54248-5052
Boiling point 302317330342.7356.5224 at 2 kPa380391.3
Density 0.7770.7770.7860.78860.7920.7780.7970.797
Flash point 148166168176

Pentacosane to triacontane

PentacosaneHexacosaneHeptacosaneOctacosaneNonacosaneTriacontane
FormulaC25H52C26H54C27H56C28H58C29H60C30H62
CAS number
Molar mass 352.69366.71380.74394.77408.80422.82
Melting point 5456.459.564.563.765.8
Boiling point 401412.2422431.6440.8449.7
Density 0.8010.7780.7800.8070.8080.810

Hentriacontane to hexatriacontane

HentriacontaneDotriacontaneTritriacontaneTetratriacontanePentatriacontaneHexatriacontane
FormulaC31H64C32H66C33H68C34H70C35H72C36H74
CAS number
Molar mass 436.85450.88464.90478.93492.96506.98
Melting point 67.96970-7272.67574-76
Boiling point 458467474285.4 at 0.4 kPa490265 at 130 Pa
Density 0.781 at 68 °C0.8120.8110.8120.8130.814

Heptatriacontane to dotetracontane

HeptatriacontaneOctatriacontaneNonatriacontaneTetracontaneHentetracontaneDotetracontane
FormulaC37H76C38H78C39H80C40H82C41H84C42H86
CAS number
Molar mass 520.99535.03549.05563.08577.11591.13
Melting point 777978848386
Boiling point 504.14510.93517.51523.88530.75536.07
Density 0.8150.8160.8170.8170.8180.819

Tritetracontane to octatetracontane

TriatetracontaneTetratetracontanePentatetracontaneHexatetracontaneHeptatetracontaneOctatetracontane
FormulaC43H88C44H90C45H92C46H94C47H96C48H98
CAS Number
Molar mass 605.15619.18633.21647.23661.26675.29
Boiling point 541.91547.57553.1558.42563.6568.68
Density 0.820.820.8210.8220.8220.823

Nonatetracontane to tetrapentacontane

NonatetracontanePentacontaneHenpentacontaneDopentacontaneTripentacontaneTetrapentacontane
FormulaC49H100C50H102C51H104C52H106C53H108C54H110
CAS number
Molar mass 689.32703.34717.37731.39745.42759.45
Boiling point 573.6578.4583587.6592596.38
Density 0.8230.8240.8240.8250.8250.826