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Names | |||
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Preferred IUPAC name Buta-1,3-diene [1] | |||
Other names
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Identifiers | |||
3D model (JSmol) | |||
605258 | |||
ChEBI | |||
ChEMBL | |||
ChemSpider | |||
ECHA InfoCard | 100.003.138 | ||
EC Number |
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25198 | |||
KEGG | |||
PubChem CID | |||
RTECS number |
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UNII | |||
UN number | 1010 | ||
CompTox Dashboard (EPA) | |||
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Properties [2] | |||
C4H6 CH2=CH-CH=CH2 | |||
Molar mass | 54.0916 g/mol | ||
Appearance | Colourless gas or refrigerated liquid | ||
Odor | Mildly aromatic or gasoline-like | ||
Density |
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Melting point | −108.91 °C (−164.04 °F; 164.24 K) | ||
Boiling point | −4.41 °C (24.06 °F; 268.74 K) | ||
1.3 g/L at 5 °C, 735 mg/L at 20 °C | |||
Solubility | |||
Vapor pressure | 2.4 atm (20 °C) [4] | ||
Refractive index (nD) | 1.4292 | ||
Viscosity | 0.25 cP at 0 °C | ||
Hazards | |||
Occupational safety and health (OHS/OSH): | |||
Main hazards | Flammable, irritative, carcinogen | ||
GHS labelling: [5] | |||
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Danger | |||
H220, H280, H340, H350 | |||
P202, P210, P280, P308+P313, P377, P381, P403 | |||
NFPA 704 (fire diamond) | |||
Flash point | −85 °C (−121 °F; 188 K) liquid flash point [4] | ||
414 °C (777 °F; 687 K) [6] | |||
Explosive limits | 2–12% | ||
Lethal dose or concentration (LD, LC): | |||
LD50 (median dose) | 548 mg/kg (rat, oral) | ||
LC50 (median concentration) | |||
LCLo (lowest published) | 250,000 ppm (rabbit, 30 min) [7] | ||
NIOSH (US health exposure limits): | |||
PEL (Permissible) | TWA 1 ppm ST 5 ppm [4] | ||
REL (Recommended) | Potential occupational carcinogen [4] | ||
IDLH (Immediate danger) | 2000 ppm [4] | ||
Safety data sheet (SDS) | ECSC 0017 | ||
Related compounds | |||
Isoprene Chloroprene | |||
Related compounds | Butane | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
1,3-Butadiene ( /ˌbjuːtəˈdaɪiːn/ ) [8] is the organic compound with the formula CH2=CH-CH=CH2. It is a colorless gas that is easily condensed to a liquid. It is important industrially as a precursor to synthetic rubber. [9] The molecule can be viewed as the union of two vinyl groups. It is the simplest conjugated diene.
Although butadiene breaks down quickly in the atmosphere, it is nevertheless found in ambient air in urban and suburban areas as a consequence of its constant emission from motor vehicles. [10]
The name butadiene can also refer to the isomer, 1,2-butadiene, which is a cumulated diene with structure H2C=C=CH−CH3. This allene has no industrial significance.
In 1863, French chemist E. Caventou isolated butadiene from the pyrolysis of amyl alcohol. [11] This hydrocarbon was identified as butadiene in 1886, after Henry Edward Armstrong isolated it from among the pyrolysis products of petroleum. [12] In 1910, the Russian chemist Sergei Lebedev polymerized butadiene and obtained a material with rubber-like properties. This polymer was, however, found to be too soft to replace natural rubber in many applications, notably automobile tires.
The butadiene industry originated in the years before World War II. Many of the belligerent nations realized that in the event of war, they could be cut off from rubber plantations controlled by the British Empire, and sought to reduce their dependence on natural rubber. [13] In 1929, Eduard Tschunker and Walter Bock, working for IG Farben in Germany, made a copolymer of styrene and butadiene that could be used in automobile tires. Worldwide production quickly ensued, with butadiene being produced from grain alcohol in the Soviet Union and the United States, and from coal-derived acetylene in Germany.
In 2020, 14.2 million tons were estimated to have been produced. [14]
In the United States, western Europe, and Japan, butadiene is produced as a byproduct of the steam cracking process used to produce ethylene and other alkenes. When mixed with steam and briefly heated to very high temperatures (often over 900 °C), aliphatic hydrocarbons give up hydrogen to produce a complex mixture of unsaturated hydrocarbons, including butadiene. The quantity of butadiene produced depends on the hydrocarbons used as feed. Light feeds, such as ethane, give primarily ethylene when cracked, but heavier feeds favor the formation of heavier olefins, butadiene, and aromatic hydrocarbons.
Butadiene is typically isolated from the other four-carbon hydrocarbons produced in steam cracking by extractive distillation using a polar aprotic solvent such as acetonitrile, N-methyl-2-pyrrolidone, furfural, or dimethylformamide, from which it is then stripped by distillation. [15]
Butadiene can also be produced by the catalytic dehydrogenation of normal butane (n-butane). The first such post-war commercial plant, producing 65,000 tons per year of butadiene, began operations in 1957 in Houston, Texas. [16] Prior to that, in the 1940s the Rubber Reserve Company, a part of the United States government, constructed several plants in Borger, Texas, Toledo, Ohio, and El Segundo, California, to produce synthetic rubber for the war effort as part of the United States Synthetic Rubber Program. [17] Total capacity was 68 KMTA (Kilo Metric Tons per Annum).
Today, butadiene from n-butane is commercially produced using the Houdry Catadiene process, which was developed during World War II. This entails treating butane over alumina and chromia at high temperatures. [18]
In other parts of the world, including South America, Eastern Europe, China, and India, butadiene is also produced from ethanol. While not competitive with steam cracking for producing large volumes of butadiene, lower capital costs make production from ethanol a viable option for smaller-capacity plants. Two processes were in use.
In the single-step process developed by Sergei Lebedev, ethanol is converted to butadiene, hydrogen, and water at 400–450 °C over any of a variety of metal oxide catalysts: [19]
This process was the basis for the Soviet Union's synthetic rubber industry during and after World War II, and it remained in limited use in Russia and other parts of eastern Europe until the end of the 1970s. At the same time this type of manufacture was canceled in Brazil. As of 2017, no butadiene was produced industrially from ethanol.
In the other, two-step process, developed by the Russian emigre chemist Ivan Ostromislensky, ethanol is oxidized to acetaldehyde, which reacts with additional ethanol over a tantalum-promoted porous silica catalyst at 325–350 °C to yield butadiene: [19]
This process was one of the three used in the United States to produce "government rubber" during World War II, although it is less economical than the butane or butene routes for the large volumes. Still, three plants with a total capacity of 200,000 tons per year were constructed in the U.S. (Institute, West Virginia, Louisville, Kentucky, and Kobuta, Pennsylvania) with start-ups completed in 1943, the Louisville plant initially created butadiene from acetylene generated by an associated calcium carbide plant. The process remains in use today in China and India.
1,3-Butadiene can also be produced by catalytic dehydrogenation of normal butenes. This method was also used by the U.S. Synthetic Rubber Program (USSRP) during World War II. The process was much more economical than the alcohol or n-butane route but competed with aviation gasoline for available butene molecules (butenes were plentiful thanks to catalytic cracking). The USSRP constructed several plants in Baton Rouge and Lake Charles, Louisiana; Houston, Baytown, and Port Neches, Texas; and Torrance, California. [17] Total annual production was 275 KMTA.
In the 1960s, a Houston company known as "Petro-Tex" patented a process to produce butadiene from normal butenes by oxidative dehydrogenation using a proprietary catalyst. It is unclear if this technology is practiced commercially. [20]
After World War II, the production from butenes became the major type of production in USSR.
1,3-Butadiene is inconvenient for laboratory use because it is gas. Laboratory procedures have been optimized for its generation from nongaseous precursors. It can be produced by the retro-Diels-Alder reaction of cyclohexene. [21] Sulfolene is a convenient solid storable source for 1,3-butadiene in the laboratory. It releases the diene and sulfur dioxide upon heating.
Most butadiene(75% of the manufactured 1,3-butadiene [9] ) is used to make synthetic rubbers for the manufacture of tyres and components of many consumer items.
The conversion of butadiene to synthetic rubbers is called polymerization, a process by which small molecules (monomers) are linked to make large ones (polymers). The mere polymerization of butadiene gives polybutadiene, which is a very soft, almost liquid material. The polymerization of butadiene and other monomers gives copolymers, which are more valued. The polymerization of butadiene and styrene and/or acrylonitrile, such as acrylonitrile butadiene styrene (ABS), nitrile-butadiene (NBR), and styrene-butadiene (SBR). These copolymers are tough and/or elastic depending on the ratio of the monomers used in their preparation. SBR is the material most commonly used for the production of automobile tyres. Precursors to still other synthetic rubbers are prepared from butadiene. One is chloroprene. [18]
Smaller amounts of butadiene are used to make adiponitrile, a precursor to some nylons. The conversion of butadiene to adiponitrile entails the addition of hydrogen cyanide to each of the double bonds in butadiene. The process is called hydrocyanation.
Butadiene is used to make the solvent sulfolane.
Butadiene is also useful in the synthesis of cycloalkanes and cycloalkenes, as it reacts with double and triple carbon-carbon bonds through Diels-Alder reactions. The most widely used such reactions involve reactions of butadiene with one or two other molecules of butadiene, i.e., dimerization and trimerization respectively. Via dimerization butadiene is converted to 4-vinylcyclohexene and cyclooctadiene. In fact, vinylcyclohexene is a common impurity that accumulates when butadiene is stored. Via trimerization, butadiene is converted to cyclododecatriene. Some of these processes employ nickel- or titanium-containing catalysts. [22]
Butadiene is also a precursor to 1-octene via palladium catalyzed telomerization with methanol. This reaction produces 1-methoxy- 2,7-octadiene as an intermediate. [14]
The most stable conformer of 1,3-butadiene is the s-trans conformation, in which the molecule is planar, with the two pairs of double bonds facing opposite directions. This conformation is most stable because orbital overlap between double bonds is maximized, allowing for maximum conjugation, while steric effects are minimized. Conventionally, the s-trans conformation is considered to have a C2-C3 dihedral angle of 180°. In contrast, the s-cis conformation, in which the dihedral angle is 0°, with the pair of double bonds facing the same direction is approximately 16.5 kJ/mol (3.9 kcal/mol) higher in energy, due to steric hindrance. This geometry is a local energy maximum, so in contrast to the s-trans geometry, it is not a conformer. The gauche geometry, in which the double bonds of the s-cis geometry are twisted to give a dihedral angle of around 38°, is a second conformer that is around 12.0 kJ/mol (2.9 kcal/mol) higher in energy than the s-trans conformer. Overall, there is a barrier of 24.8 kJ/mol (5.9 kcal/mol) for isomerization between the two conformers. [23] This increased rotational barrier and strong overall preference for a near-planar geometry is evidence for a delocalized π system and a small degree of partial double bond character in the C–C single bond, in accord with resonance theory.
Despite the high energy of the s-cis conformation, 1,3-butadiene needs to assume this conformation (or one very similar) before it can participate as the four-electron component in concerted cycloaddition reactions like the Diels-Alder reaction.
Similarly, a combined experimental and computational study has found that the double bond of s-trans-butadiene has a length of 133.8 pm, while that for ethylene has a length of 133.0 pm. This was taken as evidence of a π-bond weakened and lengthened by delocalization, as depicted by the resonance structures shown below. [24]
A qualitative picture of the molecular orbitals of 1,3-butadiene is readily obtained by applying Hückel theory. (The article on Hückel theory gives a derivation for the butadiene orbitals.)
1,3-Butadiene is also thermodynamically stabilized. While a monosubstituted double bond releases about 30.3 kcal/mol of heat upon hydrogenation, 1,3-butadiene releases slightly less (57.1 kcal/mol) than twice this energy (60.6 kcal/mol), expected for two isolated double bonds. That implies a stabilization energy of 3.5 kcal/mol. [25] Similarly, the hydrogenation of the terminal double bond of 1,4-pentadiene releases 30.1 kcal/mol of heat, while hydrogenation of the terminal double bond of conjugated (E)-1,3-pentadiene releases only 26.5 kcal/mol, implying a very similar value of 3.6 kcal/mol for the stabilization energy. [26] The ~3.5 kcal/mol difference in these heats of hydrogenation can be taken to be the resonance energy of a conjugated diene.
The industrial uses illustrate the tendency of butadiene to polymerize. Its susceptibility to 1,4-addition reactions is illustrated by its hydrocyanation. Like many dienes, it undergoes Pd-catalyzed reactions that proceed via allyl complexes. [28] It is a partner in Diels–Alder reactions, e.g. with maleic anhydride to give tetrahydrophthalic anhydride. [29]
Like other dienes, butadiene is a ligand for low-valent metal complexes, e.g. the derivatives Fe(butadiene)(CO)3 and Mo(butadiene)3.
Butadiene is of low acute toxicity. LC50 is 12.5–11.5 vol% for inhalation by rats and mice. [18]
Long-term exposure has been associated with cardiovascular disease. There is a consistent association with leukemia, as well as a significant association with other cancers. [30]
IARC has designated 1,3-butadiene as a Group 1 carcinogen ('carcinogenic to humans'), [31] and the Agency for Toxic Substances Disease Registry and the US EPA also list the chemical as a carcinogen. [32] [33] The American Conference of Governmental Industrial Hygienists (ACGIH) lists the chemical as a suspected carcinogen. [33] The Natural Resource Defense Council (NRDC) lists some disease clusters that are suspected to be associated with this chemical. [34] Some researchers have concluded it is the most potent carcinogen in cigarette smoke, twice as potent as the runner up acrylonitrile [35]
1,3-Butadiene is also a suspected human teratogen. [36] [37] [38] Prolonged and excessive exposure can affect many areas in the human body; blood, brain, eye, heart, kidney, lung, nose and throat have all been shown to react to the presence of excessive 1,3-butadiene. [39] Animal data suggest that women have a higher sensitivity to possible carcinogenic effects of butadiene over men when exposed to the chemical. This may be due to estrogen receptor impacts. While these data reveal important implications to the risks of human exposure to butadiene, more data are necessary to draw conclusive risk assessments. There is also a lack of human data for the effects of butadiene on reproductive and development shown to occur in mice, but animal studies have shown breathing butadiene during pregnancy can increase the number of birth defects, and humans have the same hormone systems as animals. [40]
1,3-Butadiene is recognized as a highly reactive volatile organic compound (HRVOC) for its potential to readily form ozone, and as such, emissions of the chemical are highly regulated by TCEQ in parts of the Houston-Brazoria-Galveston Ozone Non-Attainment Area. [41]
Properties | |
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Phase behavior | |
Triple point | 164.2 K (-109.0 °C) ? bar |
Critical point | 425 K (152 °C) 43.2 bar |
Structure | |
Symmetry group | C2h |
Gas properties | |
ΔfH0 | 110.2 kJ/mol |
Cp | 79.5 J/mol·K |
Liquid properties | |
ΔfH0 | 90.5 kJ/mol |
S0 | 199.0 J/mol·K |
Cp | 123.6 J/mol·K |
Liquid density | 0.64 ×103 kg/m3 |
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, an alkene, or olefin, is a hydrocarbon containing a carbon–carbon double bond. The double bond may be internal or in the terminal position. Terminal alkenes are also known as α-olefins.
In organic chemistry, a diene ; also diolefin, dy-OH-lə-fin) or alkadiene) is a covalent compound that contains two double bonds, usually among carbon atoms. They thus contain two alkene units, with the standard prefix di of systematic nomenclature. As a subunit of more complex molecules, dienes occur in naturally occurring and synthetic chemicals and are used in organic synthesis. Conjugated dienes are widely used as monomers in the polymer industry. Polyunsaturated fats are of interest to nutrition.
Petrochemicals are the chemical products obtained from petroleum by refining. Some chemical compounds made from petroleum are also obtained from other fossil fuels, such as coal or natural gas, or renewable sources such as maize, palm fruit or sugar cane.
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In chemistry, isomerization or isomerisation is the process in which a molecule, polyatomic ion or molecular fragment is transformed into an isomer with a different chemical structure. Enolization is an example of isomerization, as is tautomerization. When the isomerization occurs intramolecularly it may be called a rearrangement reaction.
Butene, also known as butylene, is an alkene with the formula C4H8. The word butene may refer to any of the individual compounds. They are colourless gases that are present in crude oil as a minor constituent in quantities that are too small for viable extraction. Butene is therefore obtained by catalytic cracking of long-chain hydrocarbons left during refining of crude oil. Cracking produces a mixture of products, and the butene is extracted from this by fractional distillation.
In chemistry, conformational isomerism is a form of stereoisomerism in which the isomers can be interconverted just by rotations about formally single bonds. While any two arrangements of atoms in a molecule that differ by rotation about single bonds can be referred to as different conformations, conformations that correspond to local minima on the potential energy surface are specifically called conformational isomers or conformers. Conformations that correspond to local maxima on the energy surface are the transition states between the local-minimum conformational isomers. Rotations about single bonds involve overcoming a rotational energy barrier to interconvert one conformer to another. If the energy barrier is low, there is free rotation and a sample of the compound exists as a rapidly equilibrating mixture of multiple conformers; if the energy barrier is high enough then there is restricted rotation, a molecule may exist for a relatively long time period as a stable rotational isomer or rotamer. When the time scale for interconversion is long enough for isolation of individual rotamers, the isomers are termed atropisomers. The ring-flip of substituted cyclohexanes constitutes another common form of conformational isomerism.
Isobutylene is a hydrocarbon with the chemical formula (CH3)2C=CH2. It is a four-carbon branched alkene (olefin), one of the four isomers of butylene. It is a colorless flammable gas, and is of considerable industrial value.
Chloroprene (IUPAC name 2-chlorobuta-1,3-diene) is a chemical compound with the molecular formula CH2=CCl−CH=CH2. Chloroprene is a colorless volatile liquid, almost exclusively used as a monomer for the production of the polymer polychloroprene, better known as neoprene, a type of synthetic rubber.
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Polybutadiene [butadiene rubber, BR] is a synthetic rubber. It offers high elasticity, high resistance to wear, good strength even without fillers, and excellent abrasion resistance when filled and vulcanized. "Polybutadiene" is a collective name for homopolymers formed from the polymerization of the monomer 1,3-butadiene. The IUPAC refers to polybutadiene as "poly(buta-1,3-diene)". Historically, an early generation of synthetic polybutadiene rubber produced in Germany by Bayer using sodium as a catalyst was known as "Buna rubber". Polybutadiene is typically crosslinked with sulphur, however, it has also been shown that it can be UV cured when bis-benzophenone additives are incorporated into the formulation.
A polyolefin is a type of polymer with the general formula (CH2CHR)n where R is an alkyl group. They are usually derived from a small set of simple olefins (alkenes). Dominant in a commercial sense are polyethylene and polypropylene. More specialized polyolefins include polyisobutylene and polymethylpentene. They are all colorless or white oils or solids. Many copolymers are known, such as polybutene, which derives from a mixture of different butene isomers. The name of each polyolefin indicates the olefin from which it is prepared; for example, polyethylene is derived from ethylene, and polymethylpentene is derived from 4-methyl-1-pentene. Polyolefins are not olefins themselves because the double bond of each olefin monomer is opened in order to form the polymer. Monomers having more than one double bond such as butadiene and isoprene yield polymers that contain double bonds (polybutadiene and polyisoprene) and are usually not considered polyolefins. Polyolefins are the foundations of many chemical industries.
In organic chemistry, hyperconjugation refers to the delocalization of electrons with the participation of bonds of primarily σ-character. Usually, hyperconjugation involves the interaction of the electrons in a sigma (σ) orbital with an adjacent unpopulated non-bonding p or antibonding σ* or π* orbitals to give a pair of extended molecular orbitals. However, sometimes, low-lying antibonding σ* orbitals may also interact with filled orbitals of lone pair character (n) in what is termed negative hyperconjugation. Increased electron delocalization associated with hyperconjugation increases the stability of the system. In particular, the new orbital with bonding character is stabilized, resulting in an overall stabilization of the molecule. Only electrons in bonds that are in the β position can have this sort of direct stabilizing effect — donating from a sigma bond on an atom to an orbital in another atom directly attached to it. However, extended versions of hyperconjugation can be important as well. The Baker–Nathan effect, sometimes used synonymously for hyperconjugation, is a specific application of it to certain chemical reactions or types of structures.
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trans-Cyclooctene is a cyclic hydrocarbon with the formula [–(CH2)6CH=CH–], where the two C–C single bonds adjacent to the double bond are on opposite sides of the latter's plane. It is a colorless liquid with a disagreeable odor.
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Ivan Ivanovich Ostromislensky was a Russian organic chemist. He is credited as the pioneer in studying polymerization of synthetic rubber as well as inventor of various industrial technologies for production of synthetic rubber, polymers and pharmaceuticals.
Olga Konstantinovna Bogdanova was a Soviet chemist who specialized in organic catalysis.