Names | |
---|---|
Preferred IUPAC name Hexane [1] | |
Other names Sextane, [2] hexacarbane | |
Identifiers | |
3D model (JSmol) | |
1730733 | |
ChEBI | |
ChEMBL | |
ChemSpider | |
DrugBank | |
ECHA InfoCard | 100.003.435 |
EC Number |
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1985 | |
KEGG | |
MeSH | n-hexane |
PubChem CID | |
RTECS number |
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UNII | |
UN number | 1208 |
CompTox Dashboard (EPA) | |
| |
| |
Properties | |
C6H14 | |
Molar mass | 86.178 g·mol−1 |
Appearance | Colorless liquid |
Odor | Petrolic |
Density | 0.6606 g mL−1 [3] |
Melting point | −96 to −94 °C; −141 to −137 °F; 177 to 179 K |
Boiling point | 68.5 to 69.1 °C; 155.2 to 156.3 °F; 341.6 to 342.2 K |
9.5 mg L−1 | |
log P | 3.764 |
Vapor pressure | 17.60 kPa (at 20.0 °C) |
Henry's law constant (kH) | 7.6 nmol Pa−1 kg−1 |
UV-vis (λmax) | 200 nm |
−74.6·10−6 cm3/mol | |
Refractive index (nD) | 1.375 |
Viscosity | 0.3 mPa·s |
0.08 D | |
Thermochemistry | |
Heat capacity (C) | 265.2 J K−1 mol−1 |
Std molar entropy (S⦵298) | 296.06 J K−1 mol−1 |
Std enthalpy of formation (ΔfH⦵298) | −199.4–−198.0 kJ mol−1 |
Std enthalpy of combustion (ΔcH⦵298) | −4180–−4140 kJ mol−1 |
Hazards | |
Occupational safety and health (OHS/OSH): | |
Main hazards | Reproductive toxicity – After aspiration, pulmonary oedema, pneumonitis [4] |
GHS labelling: | |
Danger | |
H225, H302, H305, H315, H336, H361fd, H373, H411 | |
P201, P202, P210, P233, P235, P240, P241, P242, P243, P260, P264, P271, P273, P280, P281, P301+P330+P331, P302+P352, P303+P361+P353, P304+P340, P308+P313, P310, P312, P314, P332+P313, P363, P370+P378, P391, P403+P233, P405, P501 | |
NFPA 704 (fire diamond) | |
Flash point | −26.0 °C (−14.8 °F; 247.2 K) |
234.0 °C (453.2 °F; 507.1 K) | |
Explosive limits | 1.2–7.7% |
Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | 25 g kg−1(oral, rat) 28710 mg/kg (rat, oral) [5] |
LDLo (lowest published) | 56137 mg/kg (rat, oral) [5] |
NIOSH (US health exposure limits): | |
PEL (Permissible) | TWA 500 ppm (1800 mg/m3) [6] |
REL (Recommended) | TWA 50 ppm (180 mg/m3) [6] |
IDLH (Immediate danger) | 1100 ppm [6] |
Related compounds | |
Related alkanes | |
Supplementary data page | |
Hexane (data page) | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Hexane ( /ˈhɛkseɪn/ ) or n-hexane is an organic compound, a straight-chain alkane with six carbon atoms and the molecular formula C6H14. [7]
Hexane is a colorless liquid, odorless when pure, and with a boiling point of approximately 69 °C (156 °F). It is widely used as a cheap, relatively safe, largely unreactive, and easily evaporated non-polar solvent, and modern gasoline blends contain about 3% hexane. [8]
The term hexanes refers to a mixture, composed largely (>60%) of n-hexane, with varying amounts of the isomeric compounds 2-methylpentane and 3-methylpentane, and possibly, smaller amounts of nonisomeric C5, C6, and C7 (cyclo)alkanes. These "hexanes" mixtures are cheaper than pure hexane and are often used in large-scale operations not requiring a single isomer (e.g., as cleaning solvent or for chromatography).
Common name | IUPAC name | Text formula | Skeletal formula |
---|---|---|---|
Normal hexane, n-Hexane | Hexane | CH3(CH2)4CH3 | |
Isohexane | 2-Methylpentane | (CH3)2CH(CH2)2CH3 | |
3-Methylpentane | CH3CH2CH(CH3)CH2CH3 | ||
2,3-Dimethylbutane | (CH3)2CHCH(CH3)2 | ||
Neohexane | 2,2-Dimethylbutane | (CH3)3CCH2CH3 |
In industry, hexanes are used in the formulation of glues for shoes, leather products, and roofing. They are also used to extract cooking oils (such as canola oil or soybean oil) from seeds, for cleansing and degreasing a variety of items, and in textile manufacturing.
A typical laboratory use of hexanes is to extract oil and grease contaminants from water and soil for analysis. [9] Since hexane cannot be easily deprotonated, it is used in the laboratory for reactions that involve very strong bases, such as the preparation of organolithiums. For example, butyllithiums are typically supplied as a hexane solution. [10]
Hexanes are commonly used in chromatography as a non-polar solvent. Higher alkanes present as impurities in hexanes have similar retention times as the solvent, meaning that fractions containing hexane will also contain these impurities. In preparative chromatography, concentration of a large volume of hexanes can result in a sample that is appreciably contaminated by alkanes. This may result in a solid compound being obtained as an oil and the alkanes may interfere with analysis.
As an internal combustion engine fuel, n-hexane has low research and motor octane numbers of 25 and 26 respectively. [11] In 1983 its share in Japanese gasoline varied around 6%, [12] in 1992 it was present in American gas between 1 and 3%, [13] and in Swedish automobile fuel in the same year the share was consistently under 2%, often below 1%. [14] By 2011 its share in US gas stood between 1 and 7%. [15]
Hexane is chiefly obtained by refining crude oil. The exact composition of the fraction depends largely on the source of the oil (crude or reformed) and the constraints of the refining. [16] The industrial product (usually around 50% by weight of the straight-chain isomer) is the fraction boiling at 65–70 °C (149–158 °F).
All alkanes are colorless. [17] [18] The boiling points of the various hexanes are somewhat similar and, as for other alkanes, are generally lower for the more branched forms. The melting points are quite different and the trend is not apparent. [19]
Isomer | M.P. (°C) | M.P. (°F) | B.P. (°C) | B.P. (°F) |
---|---|---|---|---|
n-hexane | −95.3 | −139.5 | 68.7 | 155.7 |
3-methylpentane | −118.0 | −180.4 | 63.3 | 145.9 |
2-methylpentane (isohexane) | −153.7 | −244.7 | 60.3 | 140.5 |
2,3-dimethylbutane | −128.6 | −199.5 | 58.0 | 136.4 |
2,2-dimethylbutane (neohexane) | −99.8 | −147.6 | 49.7 | 121.5 |
Hexane has considerable vapor pressure at room temperature:
Temperature (°C) | Temperature (°F) | Vapor pressure (mmHg) | Vapor pressure (kPa) |
---|---|---|---|
−40 | −40 | 3.36 | 0.448 |
−30 | −22 | 7.12 | 0.949 |
−20 | −4 | 14.01 | 1.868 |
−10 | 14 | 25.91 | 3.454 |
0 | 32 | 45.37 | 6.049 |
10 | 50 | 75.74 | 10.098 |
20 | 68 | 121.26 | 16.167 |
25 | 77 | 151.28 | 20.169 |
30 | 86 | 187.11 | 24.946 |
40 | 104 | 279.42 | 37.253 |
50 | 122 | 405.31 | 54.037 |
60 | 140 | 572.76 | 76.362 |
Like most alkanes, hexanes characteristically exhibit low reactivity and are suitable solvents for reactive compounds. Commercial samples of n-hexane however often contains methylcyclopentane, which features tertiary C-H bonds, which are incompatible with some radical reactions. [20]
Inhalation of n-hexane at 5000 ppm for 10 minutes produces marked vertigo; 2500-1000 ppm for 12 hours produces drowsiness, fatigue, loss of appetite, and paresthesia in the distal extremities; 2500–5000 ppm produces muscle weakness, cold pulsation in the extremities, blurred vision, headache, and anorexia. [21] Chronic occupational exposure to elevated levels of n-hexane has been demonstrated to be associated with peripheral neuropathy in auto mechanics in the US, and neurotoxicity in workers in printing presses, and shoe and furniture factories in Asia, Europe, and North America. [22]
The US National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) for hexane isomers (not n-hexane) of 100 ppm (350 mg/m3 (0.15 gr/cu ft)) over an 8-hour workday. [23] However, for n-hexane, the current NIOSH REL is 50 ppm (180 mg/m3 (0.079 gr/cu ft)) over an 8-hour workday. [24] This limit was proposed as a permissible exposure limit (PEL) by the Occupational Safety and Health Administration in 1989; however, this PEL was overruled in US courts in 1992. [25] The current n-hexane PEL in the US is 500 ppm (1,800 mg/m3 (0.79 gr/cu ft)). [24]
Hexane and other volatile hydrocarbons (petroleum ether) present an aspiration risk. [26] n-Hexane is sometimes used as a denaturant for alcohol, and as a cleaning agent in the textile, furniture, and leather industries. It is slowly being replaced with other solvents. [27]
Like gasoline, hexane is highly volatile and is an explosion risk. The 1981 Louisville sewer explosions, which destroyed over 13 mi (21 km) of sewer lines and streets in Kentucky, were caused by ignition of hexane vapors which had been illegally discharged from a soybean processing plant owned by Ralston-Purina. Hexane was attributed as the cause of an explosion that occurred in the National University of Río Cuarto, Argentina on 5 December 2007, due to a hexane spill near a heat-producing machine that exploded, producing a fire that killed one student and injured 24 more.
Occupational hexane poisoning has occurred with Japanese sandal workers, Italian shoe workers, [28] Taiwan press proofing workers, and others. [29] Analysis of Taiwanese workers has shown occupational exposure to substances including n-hexane. [30] In 2010–2011, Chinese workers manufacturing iPhones were reported to have suffered hexane poisoning. [31] [32]
n-Hexane is biotransformed to 2-hexanol and further to 2,5-hexanediol in the body. The conversion is catalyzed by the enzyme cytochrome P450 utilizing oxygen from air. 2,5-Hexanediol may be further oxidized to 2,5-hexanedione, which is neurotoxic and produces a polyneuropathy. [27] In view of this behavior, replacement of n-hexane as a solvent has been discussed. n-Heptane is a possible alternative. [33]
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.
Naphthalene is an organic compound with formula C
10H
8. It is the simplest polycyclic aromatic hydrocarbon, and is a white crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 ppm by mass. As an aromatic hydrocarbon, naphthalene's structure consists of a fused pair of benzene rings. It is the main ingredient of traditional mothballs.
In organic chemistry, xylene or xylol are any of three organic compounds with the formula (CH3)2C6H4. They are derived from the substitution of two hydrogen atoms with methyl groups in a benzene ring; which hydrogens are substituted determines which of three structural isomers results. It is a colorless, flammable, slightly greasy liquid of great industrial value.
Octane is a hydrocarbon and an alkane with the chemical formula C8H18, and the condensed structural formula CH3(CH2)6CH3. Octane has many structural isomers that differ by the location of branching in the carbon chain. One of these isomers, 2,2,4-trimethylpentane (commonly called iso-octane), is used as one of the standard values in the octane rating scale.
Heptane or n-heptane is the straight-chain alkane with the chemical formula H3C(CH2)5CH3 or C7H16. When used as a test fuel component in anti-knock test engines, a 100% heptane fuel is the zero point of the octane rating scale (the 100 point is 100% iso-octane). Octane number equates to the anti-knock qualities of a comparison mixture of heptane and iso-octane which is expressed as the percentage of iso-octane in heptane, and is listed on pumps for gasoline (petrol) dispensed globally.
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.
An oil refinery or petroleum refinery is an industrial process plant where petroleum is transformed and refined into products such as gasoline (petrol), diesel fuel, asphalt base, fuel oils, heating oil, kerosene, liquefied petroleum gas and petroleum naphtha. Petrochemical feedstock like ethylene and propylene can also be produced directly by cracking crude oil without the need of using refined products of crude oil such as naphtha. The crude oil feedstock has typically been processed by an oil production plant. There is usually an oil depot at or near an oil refinery for the storage of incoming crude oil feedstock as well as bulk liquid products. In 2020, the total capacity of global refineries for crude oil was about 101.2 million barrels per day.
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 diesel fuel.
White spirit (AU, UK and Ireland) or mineral spirits (US, Canada), also known as mineral turpentine (AU/NZ/ZA), turpentine substitute, and petroleum spirits, is a petroleum-derived clear liquid used as a common organic solvent in painting. There are also terms for specific kinds of white spirit, including Stoddard solvent and solvent naphtha (petroleum). White spirit is often used as a paint thinner, or as a component thereof, though paint thinner is a broader category of solvent. Odorless mineral spirits (OMS) have been refined to remove the more toxic aromatic compounds, and are recommended for applications such as oil painting.
Ethylbenzene is an organic compound with the formula C6H5CH2CH3. It is a highly flammable, colorless liquid with an odor similar to that of gasoline. This monocyclic aromatic hydrocarbon is important in the petrochemical industry as a reaction intermediate in the production of styrene, the precursor to polystyrene, a common plastic material. In 2012, more than 99% of ethylbenzene produced was consumed in the production of styrene.
2,2-Dimethylbutane, trivially known as neohexane at William Odling's 1876 suggestion, is an organic compound with formula C6H14 or (H3C-)3-C-CH2-CH3. It is therefore an alkane, indeed the most compact and branched of the hexane isomers — the only one with a quaternary carbon and a butane (C4) backbone.
1-Butanol, also known as butan-1-ol or n-butanol, is a primary alcohol with the chemical formula C4H9OH and a linear structure. Isomers of 1-butanol are isobutanol, butan-2-ol and tert-butanol. The unmodified term butanol usually refers to the straight chain isomer.
1,2-Dichlorobenzene, or orthodichlorobenzene (ODCB), is an aryl chloride and isomer of dichlorobenzene with the formula C6H4Cl2. This colourless liquid is poorly soluble in water but miscible with most organic solvents. It is a derivative of benzene, consisting of two adjacent chlorine atoms.
1,2,4-Trichlorobenzene is an organochlorine compound, one of three isomers of trichlorobenzene. It is a derivative of benzene with three chloride substituents. It is a colorless liquid used as a solvent for a variety of compounds and materials.
3-Methylpentane is a branched alkane with the molecular formula C6H14. It is a structural isomer of hexane composed of a methyl group bonded to the third carbon atom in a pentane chain. It is of similar structure to the isomeric 2-methylpentane, which has the methyl group located on the second carbon of the pentane chain.
2-Methylpentane, trivially known as isohexane, is a branched-chain alkane with the molecular formula C6H14. It is a structural isomer of hexane composed of a methyl group bonded to the second carbon atom in a pentane chain.
Butane is an alkane with the formula C4H10. Butane exists as two isomers, n-butane with connectivity CH3CH2CH2CH3 and iso-butane with the formula (CH3)3CH. Both isomers are highly flammable, colorless, easily liquefied gases that quickly vaporize at room temperature and pressure. Butanes are a trace components of natural gases (NG gases). The other hydrocarbons in NG include propane, ethane, and especially methane, which are more abundant. Liquefied petroleum gas is a mixture of propane and some butanes.
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.
Petroleum benzine is a hydrocarbon-based solvent mixture that is classified by its physical properties rather than a specific chemical composition. This complicates distinction within the long list of petroleum distillate solvent mixtures: mineral spirits, naphtha, petroleum naptha, white gas, white spirits, turps substitute, mineral turpentine, petroleum ether, ligroin, and Stoddard solvent.