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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? ]
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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.
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.
Some alkanes have non-IUPAC trivial names:
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).
This group of n-alkanes is generally liquid under standard conditions. [4]
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% | |||||
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 | 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 | 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 [5] | 0.812 | 0.811 | 0.812 | 0.813 | 0.814 |
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 |
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 | 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 | 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 |
In organic chemistry, an alkane, or paraffin, is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in which all the carbon–carbon bonds are single. Alkanes have the general chemical formula CnH2n+2. The alkanes range in complexity from the simplest case of methane, where n = 1, to arbitrarily large and complex molecules, like pentacontane or 6-ethyl-2-methyl-5-(1-methylethyl) octane, an isomer of tetradecane.
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic; their odor is usually faint, and may be similar to that of gasoline or lighter fluid. They occur in a diverse range of molecular structures and phases: they can be gases, liquids, low melting solids or polymers.
Kerosene, or paraffin, is a combustible hydrocarbon liquid which is derived from petroleum. It is widely used as a fuel in aviation as well as households. Its name derives from κηρός (kērós) meaning "wax", and was registered as a trademark by Nova Scotia geologist and inventor Abraham Gesner in 1854 before evolving into a generic trademark. It is sometimes spelled kerosine in scientific and industrial usage.
Paraffin wax is a soft colorless solid derived from petroleum, coal, or oil shale that consists of a mixture of hydrocarbon molecules containing between 20 and 40 carbon atoms. It is solid at room temperature and begins to melt above approximately 37 °C (99 °F), and its boiling point is above 370 °C (698 °F). Common applications for paraffin wax include lubrication, electrical insulation, and candles; dyed paraffin wax can be made into crayons.
Waxes are a diverse class of organic compounds that are lipophilic, malleable solids near ambient temperatures. They include higher alkanes and lipids, typically with melting points above about 40 °C (104 °F), melting to give low viscosity liquids. Waxes are insoluble in water but soluble in nonpolar organic solvents such as hexane, benzene and chloroform. Natural waxes of different types are produced by plants and animals and occur in petroleum.
Diesel fuel, also called diesel oil, heavy oil (historically) or simply diesel, is any liquid fuel specifically designed for use in a diesel engine, a type of internal combustion engine in which fuel ignition takes place without a spark as a result of compression of the inlet air and then injection of fuel. Therefore, diesel fuel needs good compression ignition characteristics.
Naphtha is a flammable liquid hydrocarbon mixture. Generally, it is a fraction of crude oil, but it can also be produced from natural-gas condensates, petroleum distillates, and the fractional distillation of coal tar and peat. In some industries and regions, the name naphtha refers to crude oil or refined petroleum products such as kerosene or diesel fuel.
RP-1 (alternatively, Rocket Propellant-1 or Refined Petroleum-1) is a highly refined form of kerosene outwardly similar to jet fuel, used as rocket fuel. RP-1 provides a lower specific impulse than liquid hydrogen (H2), but is cheaper, is stable at room temperature, and presents a lower explosion hazard. RP-1 is far denser than H2, giving it a higher energy density (though its specific energy is lower). RP-1 also has a fraction of the toxicity and carcinogenic hazards of hydrazine, another room-temperature liquid fuel.
Pentane is an organic compound with the formula C5H12—that is, an alkane with five carbon atoms. The term may refer to any of three structural isomers, or to a mixture of them: in the IUPAC nomenclature, however, pentane means exclusively the n-pentane isomer, in which case pentanes refers to a mixture of them; the other two are called isopentane (methylbutane) and neopentane (dimethylpropane). Cyclopentane is not an isomer of pentane because it has only 10 hydrogen atoms where pentane has 12.
Nonane is a linear alkane hydrocarbon with the chemical formula C9H20. It is a colorless, flammable liquid, occurring primarily in the component of the petroleum distillate fraction commonly called kerosene, which is used as a heating, tractor, and jet fuel. Nonane is also used as a solvent, distillation chaser, fuel additive, and a component in biodegradable detergents. It is also a minor component of the diesel fuel.
Liquid fuels are combustible or energy-generating molecules that can be harnessed to create mechanical energy, usually producing kinetic energy; they also must take the shape of their container. It is the fumes of liquid fuels that are flammable instead of the fluid. Most liquid fuels in widespread use are derived from fossil fuels; however, there are several types, such as hydrogen fuel, ethanol, and biodiesel, which are also categorized as a liquid fuel. Many liquid fuels play a primary role in transportation and the economy.
Cetane number (CN) is an indicator of the combustion speed of diesel fuel and compression needed for ignition. It plays a similar role for diesel as octane rating does for gasoline. The CN is an important factor in determining the quality of diesel fuel, but not the only one; other measurements of diesel fuel's quality include energy content, density, lubricity, cold-flow properties and sulfur content.
Hexadecane (also called cetane) is an alkane hydrocarbon with the chemical formula C16H34. Hexadecane consists of a chain of 16 carbon atoms, with three hydrogen atoms bonded to the two end carbon atoms, and two hydrogens bonded to each of the 14 other carbon atoms.
The Fischer–Tropsch process (FT) is a collection of chemical reactions that converts a mixture of carbon monoxide and hydrogen, known as syngas, into liquid hydrocarbons. These reactions occur in the presence of metal catalysts, typically at temperatures of 150–300 °C (302–572 °F) and pressures of one to several tens of atmospheres. The Fischer–Tropsch process is an important reaction in both coal liquefaction and gas to liquids technology for producing liquid hydrocarbons.
Petroleum products are materials derived from crude oil (petroleum) as it is processed in oil refineries. Unlike petrochemicals, which are a collection of well-defined usually pure organic compounds, petroleum products are complex mixtures. Most petroleum is converted into petroleum products, which include several classes of fuels.
Petroleum geochemistry is a branch of geochemistry which deals specifically with petroleum and its origin, generation, and accumulation, as well as its extraction, refinement, and use. Petroleum, also known as crude oil, is a solid, liquid, and/or gaesous mix of hydrocarbons. These hydrocarbons are from the burial and metamorphosis of organic matter from millions of years ago; the organic matter is from marine animals, plants, and algae. Petroleum is extracted from the Earth, refined, and used as an energy source.
Catalytic reforming is a chemical process used to convert naphthas from crude oil into liquid products called reformates, which are premium "blending stocks" for high-octane gasoline. The process converts low-octane linear hydrocarbons (paraffins) into branched alkanes (isoparaffins) and cyclic naphthenes, which are then partially dehydrogenated to produce high-octane aromatic hydrocarbons. The dehydrogenation also produces significant amounts of byproduct hydrogen gas, which is fed into other refinery processes such as hydrocracking. A side reaction is hydrogenolysis, which produces light hydrocarbons of lower value, such as methane, ethane, propane and butanes.
In chemistry, volatility is a material quality which describes how readily a substance vaporizes. At a given temperature and pressure, a substance with high volatility is more likely to exist as a vapour, while a substance with low volatility is more likely to be a liquid or solid. Volatility can also describe the tendency of a vapor to condense into a liquid or solid; less volatile substances will more readily condense from a vapor than highly volatile ones. Differences in volatility can be observed by comparing how fast substances within a group evaporate when exposed to the atmosphere. A highly volatile substance such as rubbing alcohol will quickly evaporate, while a substance with low volatility such as vegetable oil will remain condensed. In general, solids are much less volatile than liquids, but there are some exceptions. Solids that sublimate such as dry ice or iodine can vaporize at a similar rate as some liquids under standard conditions.
Crude oil is extracted from the bedrock before being processed in several stages, removing natural contaminants and undesirable hydrocarbons. This separation process produces mineral oil, which can in turn be denoted as paraffinic, naphthenic or aromatic. The differences between these different types of oils are not clear-cut, but mainly depend on the predominant hydrocarbon types in the oil. Paraffinic oil, for example, contains primarily higher alkanes, whereas naphthenic oils have a high share of cyclic alkanes in the mixture.
Petroleum naphtha is an intermediate hydrocarbon liquid stream derived from the refining of crude oil with CAS-no 64742-48-9. It is most usually desulfurized and then catalytically reformed, which rearranges or restructures the hydrocarbon molecules in the naphtha as well as breaking some of the molecules into smaller molecules to produce a high-octane component of gasoline.