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Names | |||
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IUPAC name Styrene [1] | |||
Systematic IUPAC name Ethenylbenzene [2] | |||
Other names | |||
Identifiers | |||
3D model (JSmol) | |||
1071236 | |||
ChEBI | |||
ChEMBL | |||
ChemSpider | |||
ECHA InfoCard | 100.002.592 | ||
EC Number |
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2991 | |||
KEGG | |||
PubChem CID | |||
RTECS number |
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UNII | |||
UN number | 2055 | ||
CompTox Dashboard (EPA) | |||
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Properties | |||
C8H8 | |||
Molar mass | 104.15 g/mol | ||
Appearance | colorless oily liquid | ||
Odor | sweet, floral [3] | ||
Density | 0.909 g/cm3 | ||
Melting point | −30 °C (−22 °F; 243 K) | ||
Boiling point | 145 °C (293 °F; 418 K) | ||
0.03% (20 °C) [3] | |||
log P | 2.70 [4] | ||
Vapor pressure | 5 mmHg (20 °C) [3] | ||
−6.82×10−5 cm3/mol | |||
Refractive index (nD) | 1.5469 | ||
Viscosity | 0.762 cP at 20 °C | ||
Structure | |||
0.13 D | |||
Hazards | |||
Occupational safety and health (OHS/OSH): | |||
Main hazards | flammable, toxic, probably carcinogenic | ||
GHS labelling: | |||
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Danger | |||
H226, H315, H319, H332, H361, H372 | |||
P201, P202, P210, P233, P240, P241, P242, P243, P260, P261, P264, P270, P271, P280, P281, P302+P352, P303+P361+P353, P304+P312, P304+P340, P305+P351+P338, P308+P313, P312, P314, P321, P332+P313, P337+P313, P362, P370+P378, P403+P235, P405, P501 | |||
NFPA 704 (fire diamond) | |||
Flash point | 31 °C (88 °F; 304 K) | ||
Explosive limits | 0.9–6.8% [3] | ||
Lethal dose or concentration (LD, LC): | |||
LC50 (median concentration) | 2194 ppm (mouse, 4 h) 5543 ppm (rat, 4 h) [5] | ||
LCLo (lowest published) | 10,000 ppm (human, 30 min) 2771 ppm (rat, 4 h) [5] | ||
NIOSH (US health exposure limits): | |||
PEL (Permissible) | TWA 100 ppm C 200 ppm 600 ppm (5-minute maximum peak in any 3 hours) [3] | ||
REL (Recommended) | TWA 50 ppm (215 mg/m3) ST 100 ppm (425 mg/m3) [3] | ||
IDLH (Immediate danger) | 700 ppm [3] | ||
Safety data sheet (SDS) | MSDS | ||
Related compounds | |||
Related styrenes; related aromatic compounds | polystyrene, stilbene; ethylbenzene | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Styrene is an organic compound with the chemical formula C6H5CH=CH2. Its structure consists of a vinyl group as substituent on benzene. Styrene is a colorless, oily liquid, although aged samples can appear yellowish. The compound evaporates easily and has a sweet smell, although high concentrations have a less pleasant odor.[ vague ] Styrene is the precursor to polystyrene and several copolymers, and is typically made from benzene for this purpose. Approximately 25 million tonnes of styrene were produced in 2010, [6] increasing to around 35 million tonnes by 2018.
Styrene is named after storax balsam (often commercially sold as styrax), the resin of Liquidambar trees of the Altingiaceae plant family. Styrene occurs naturally in small quantities in some plants and foods (cinnamon, coffee beans, balsam trees and peanuts) [7] and is also found in coal tar.
In 1839, the German apothecary Eduard Simon isolated a volatile liquid from the resin (called storax or styrax (Latin)) of the American sweetgum tree ( Liquidambar styraciflua ). He called the liquid "styrol" (now called styrene). [8] [9] He also noticed that when styrol was exposed to air, light, or heat, it gradually transformed into a hard, rubber-like substance, which he called "styrol oxide". [10]
By 1845, the German chemist August Wilhelm von Hofmann and his student John Buddle Blyth had determined styrene's empirical formula: C8H8. [11] They had also determined that Simon's "styrol oxide" – which they renamed "metastyrol" – had the same empirical formula as styrene. [12] Furthermore, they could obtain styrene by dry-distilling "metastyrol". [13]
In 1865, the German chemist Emil Erlenmeyer found that styrene could form a dimer, [14] and in 1866 the French chemist Marcelin Berthelot stated that "metastyrol" was a polymer of styrene (i.e. polystyrene). [15] Meanwhile, other chemists had been investigating another component of storax, namely, cinnamic acid. They had found that cinnamic acid could be decarboxylated to form "cinnamene" (or "cinnamol"), which appeared to be styrene.
In 1845, French chemist Emil Kopp suggested that the two compounds were identical, [16] and in 1866, Erlenmeyer suggested that both "cinnamol" and styrene might be vinylbenzene. [17] However, the styrene that was obtained from cinnamic acid seemed different from the styrene that was obtained by distilling storax resin: the latter was optically active. [18] Eventually, in 1876, the Dutch chemist van 't Hoff resolved the ambiguity: the optical activity of the styrene that was obtained by distilling storax resin was due to a contaminant. [19]
The vast majority of styrene is produced from ethylbenzene, [20] and almost all ethylbenzene produced worldwide is intended for styrene production. As such, the two production processes are often highly integrated. Ethylbenzene is produced via a Friedel–Crafts reaction between benzene and ethene; originally this used aluminum chloride as a catalyst, but in modern production this has been replaced by zeolites.
Around 80% of styrene is produced by the dehydrogenation of ethylbenzene. This is achieved using superheated steam (up to 600 °C) over an iron(III) oxide catalyst. [21] The reaction is highly endothermic and reversible, with a typical yield of 88–94%.
The crude ethylbenzene/styrene product is then purified by distillation. As the difference in boiling points between the two compounds is only 9 °C at ambient pressure this necessitates the use of a series of distillation columns. This is energy intensive and is further complicated by the tendency of styrene to undergo thermally induced polymerisation into polystyrene, [22] requiring the continuous addition of polymerization inhibitor to the system.
Styrene is also co-produced commercially in a process known as POSM (Lyondell Chemical Company) or SM/PO (Shell) for styrene monomer / propylene oxide. In this process, ethylbenzene is treated with oxygen to form the ethylbenzene hydroperoxide. This hydroperoxide is then used to oxidize propylene to propylene oxide, which is also recovered as a co-product. The remaining 1-phenylethanol is dehydrated to give styrene:
Extraction from pyrolysis gasoline is performed on a limited scale. [20]
Styrene can be produced from toluene and methanol, which are cheaper raw materials than those in the conventional process. This process has suffered from low selectivity associated with the competing decomposition of methanol. [23] Exelus Inc. claims to have developed this process with commercially viable selectivities, at 400–425 °C and atmospheric pressure, by forcing these components through a proprietary zeolitic catalyst. It is reported [24] that an approximately 9:1 mixture of styrene and ethylbenzene is obtained, with a total styrene yield of over 60%. [25]
Another route to styrene involves the reaction of benzene and ethane. This process is being developed by Snamprogetti and Dow. Ethane, along with ethylbenzene, is fed to a dehydrogenation reactor with a catalyst capable of simultaneously producing styrene and ethylene. The dehydrogenation effluent is cooled and separated and the ethylene stream is recycled to the alkylation unit. The process attempts to overcome previous shortcomings in earlier attempts to develop production of styrene from ethane and benzene, such as inefficient recovery of aromatics, production of high levels of heavies and tars, and inefficient separation of hydrogen and ethane. Development of the process is ongoing. [26]
A laboratory synthesis of styrene entails the decarboxylation of cinnamic acid: [27]
Styrene was first prepared by this method. [28]
The presence of the vinyl group allows styrene to polymerize. Commercially significant products include polystyrene, acrylonitrile butadiene styrene (ABS), styrene-butadiene rubber (SBR), styrene-butadiene latex, SIS (styrene-isoprene-styrene), S-EB-S (styrene-ethylene/butylene-styrene), styrene-divinylbenzene (S-DVB), styrene-acrylonitrile resin (SAN), and unsaturated polyesters used in resins and thermosetting compounds. These materials are used in rubber, plastic, insulation, fiberglass, pipes, automobile and boat parts, food containers, and carpet backing.
As a liquid or a gas, pure styrene will polymerise spontaneously to polystyrene, without the need of external initiators. [29] This is known as autopolymerisation. At 100 °C it will autopolymerise at a rate of ~2% per hour, and more rapidly than this at higher temperatures. [22] As the autopolymerisation reaction is exothermic it can be self-accelerating, with a real risk of a thermal runaway, potentially leading to an explosion. Examples include the 2019 explosion of the tanker Stolt Groenland, [30] explosions at the Phillips Petroleum Company in 1999 and 2000 and overheating styrene tanks leading to the 2020 Visakhapatnam gas leak, which killed several people. [31] [32] The autopolymerisation reaction can only be kept in check by the continuous addition of polymerisation inhibitors.
Styrene is regarded as a "known carcinogen", especially in case of eye contact, but also in case of skin contact, of ingestion and of inhalation, according to several sources. [20] [33] [34] [35] Styrene is largely metabolized into styrene oxide in humans, resulting from oxidation by cytochrome P450. Styrene oxide is considered toxic, mutagenic, and possibly carcinogenic. Styrene oxide is subsequently hydrolyzed in vivo to styrene glycol by the enzyme epoxide hydrolase. [36] The US Environmental Protection Agency (EPA) has described styrene to be "a suspected toxin to the gastrointestinal tract, kidney, and respiratory system, among others". [37] [38]
On 10 June 2011, the US National Toxicology Program has described styrene as "reasonably anticipated to be a human carcinogen". [39] [40] However, a STATS author describes [41] a review that was done on scientific literature and concluded that "The available epidemiologic evidence does not support a causal relationship between styrene exposure and any type of human cancer". [42] Despite this claim, work has been done by Danish researchers to investigate the relationship between occupational exposure to styrene and cancer. They concluded, "The findings have to be interpreted with caution, due to the company based exposure assessment, but the possible association between exposures in the reinforced plastics industry, mainly styrene, and degenerative disorders of the nervous system and pancreatic cancer, deserves attention". [43] In 2012, the Danish EPA concluded that the styrene data do not support a cancer concern for styrene. [44] The US EPA does not have a cancer classification for styrene, [45] but it has been the subject of their Integrated Risk Information System (IRIS) program. [46]
The National Toxicology Program of the US Department of Health and Human Services has determined that styrene is "reasonably anticipated to be a human carcinogen". [47] Various regulatory bodies refer to styrene, in various contexts, as a possible or potential human carcinogen. The International Agency for Research on Cancer considers styrene to be "probably carcinogenic to humans". [48] [49]
The neurotoxic [50] properties of styrene have also been studied and reported effects include effects on vision [51] (although unable to reproduce in a subsequent study [52] ) and on hearing functions. [53] [54] [55] [56] Studies on rats have yielded contradictory results, [54] [55] but epidemiologic studies have observed a synergistic interaction with noise in causing hearing difficulties. [57] [58] [59] [60]
Toluene, also known as toluol, is a substituted aromatic hydrocarbon with the chemical formula C6H5CH3, often abbreviated as PhCH3, where Ph stands for the phenyl group. It is a colorless, water-insoluble liquid with the odor associated with paint thinners. It is a mono-substituted benzene derivative, consisting of a methyl group (CH3) attached to a phenyl group by a single bond. As such, its systematic IUPAC name is methylbenzene. Toluene is predominantly used as an industrial feedstock and a solvent.
Formaldehyde ( for-MAL-di-hide, fər-) (systematic name methanal) is an organic compound with the chemical formula CH2O and structure H−CHO, more precisely H2C=O. The compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde. It is stored as aqueous solutions (formalin), which consists mainly of the hydrate CH2(OH)2. It is the simplest of the aldehydes (R−CHO). As a precursor to many other materials and chemical compounds, in 2006 the global production of formaldehyde was estimated at 12 million tons per year. It is mainly used in the production of industrial resins, e.g., for particle board and coatings. Small amounts also occur naturally.
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.
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.
Butanone, also known as methyl ethyl ketone (MEK) or ethyl methyl ketone, is an organic compound with the formula CH3C(O)CH2CH3. This colorless liquid ketone has a sharp, sweet odor reminiscent of acetone. It is produced industrially on a large scale, but occurs in nature only in trace amounts. It is partially soluble in water, and is commonly used as an industrial solvent. It is an isomer of another solvent, tetrahydrofuran.
Polystyrene (PS) is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It is a poor barrier to air and water vapor and has a relatively low melting point. Polystyrene is one of the most widely used plastics, with the scale of its production being several million tonnes per year. Polystyrene is naturally transparent, but can be colored with colorants. Uses include protective packaging, containers, lids, bottles, trays, tumblers, disposable cutlery, in the making of models, and as an alternative material for phonograph records.
Acrylonitrile butadiene styrene (ABS) (chemical formula (C8H8)x·(C4H6)y·(C3H3N)z ) is a common thermoplastic polymer. Its glass transition temperature is approximately 105 °C (221 °F). ABS is amorphous and therefore has no true melting point.
1,4-Dichlorobenzene (1,4-DCB, p-DCB, or para-dichlorobenzene, sometimes abbreviated as PDCB or para) is an aryl chloride and isomer of dichlorobenzene with the formula C6H4Cl2. This colorless solid has a strong odor. The molecule consists of a benzene ring with two chlorine atoms (replacing hydrogen atoms) on opposing sites of the ring.
Chloroethane, commonly known as ethyl chloride, is a chemical compound with chemical formula CH3CH2Cl, once widely used in producing tetraethyllead, a gasoline additive. It is a colorless, flammable gas or refrigerated liquid with a faintly sweet odor.
Acrylonitrile is an organic compound with the formula CH2CHCN and the structure H2C=CH−C≡N. It is a colorless, volatile liquid. It has a pungent odor of garlic or onions. Its molecular structure consists of a vinyl group linked to a nitrile. It is an important monomer for the manufacture of useful plastics such as polyacrylonitrile. It is reactive and toxic at low doses.
1,3-Butadiene 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. The molecule can be viewed as the union of two vinyl groups. It is the simplest conjugated diene.
Propylene oxide is an acutely toxic and carcinogenic organic compound with the molecular formula C3H6O. This colourless volatile liquid with an odour similar to ether, is produced on a large scale industrially. Its major application is its use for the production of polyether polyols for use in making polyurethane plastics. It is a chiral epoxide, although it is commonly used as a racemic mixture.
Nitrobenzene is an aromatic nitro compound and the simplest of the nitrobenzenes, with the chemical formula C6H5NO2. It is a water-insoluble pale yellow oil with an almond-like odor. It freezes to give greenish-yellow crystals. It is produced on a large scale from benzene as a precursor to aniline. In the laboratory, it is occasionally used as a solvent, especially for electrophilic reagents. As confirmed by X-ray crystallography, nitrobenzene is a planar molecule.
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.
p-Xylene (para-xylene) is an aromatic hydrocarbon. It is one of the three isomers of dimethylbenzene known collectively as xylenes. The p- stands for para-, indicating that the two methyl groups in p-xylene occupy the diametrically opposite substituent positions 1 and 4. It is in the positions of the two methyl groups, their arene substitution pattern, that it differs from the other isomers, o-xylene and m-xylene. All have the same chemical formula C6H4(CH3)2. All xylene isomers are colorless and highly flammable. The odor threshold of p-xylene is 0.62 parts per million (ppm).
Storax, often commercially sold as styrax, is a natural fragrant resin isolated from the wounded bark of Liquidambar orientalis Mill. and Liquidambar styraciflua L. (Altingiaceae). It is distinct from benzoin, a similar resin obtained from the Styracaceae plant family.
Glycidol is an organic compound with the formula HOCH2CHOCH2. The molecule contains both epoxide and alcohol functional groups. Being simple to make and bifunctional, it has a variety of industrial uses. The compound is a colorless, slightly viscous liquid that is slightly unstable and is not often encountered in pure form.
Ethyl acrylate is an organic compound with the formula CH2CHCO2CH2CH3. It is the ethyl ester of acrylic acid. It is a colourless liquid with a characteristic acrid odor. It is mainly produced for paints, textiles, and non-woven fibers. It is also a reagent in the synthesis of various pharmaceutical intermediates.
Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar hexagonal ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms, benzene is classed as a hydrocarbon.
John Buddle Blyth was a Jamaican-born chemist who was the first professor of chemistry at Queen's College Cork in Ireland. With August Wilhelm von Hofmann, he was the first to report photopolymerisation which they observed when styrene became metastyrol after exposure to sunlight.
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