Benzene
Space-filling model
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Benzene at room temperature
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Names | |||
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Preferred IUPAC name
Benzene[1] | |||
Other names
Benzol (historic/German)
Phenane Phenylene hydride Cyclohexa-1,3,5-triene; 1,3,5-Cyclohexatriene (theoretical resonance isomers) [6]Annulene (not recommended[1]) Phene (historic) | |||
Identifiers | |||
3D model (
JSmol ) |
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ChEBI | |||
ChEMBL | |||
ChemSpider | |||
ECHA InfoCard
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100.000.685 | ||
EC Number |
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KEGG | |||
PubChem CID
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RTECS number
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UNII | |||
CompTox Dashboard (EPA)
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Properties | |||
C6H6 | |||
Molar mass | 78.114 g·mol−1 | ||
Appearance | Colorless liquid | ||
Odor | sweet aromatic | ||
Density | 0.8765(20) g/cm3[2] | ||
Melting point | 5.53 °C (41.95 °F; 278.68 K) | ||
Boiling point | 80.1 °C (176.2 °F; 353.2 K) | ||
1.53 g/L (0 °C) 1.81 g/L (9 °C) 1.79 g/L (15 °C)[3][4][5] 1.84 g/L (30 °C) 2.26 g/L (61 °C) 3.94 g/L (100 °C) 21.7 g/kg (200 °C, 6.5 MPa) 17.8 g/kg (200 °C, 40 MPa)[6] | |||
Solubility | Soluble in alcohol, CHCl3, CCl4, diethyl ether, acetone, acetic acid[6] | ||
ethanediol
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5.83 g/100 g (20 °C) 6.61 g/100 g (40 °C) 7.61 g/100 g (60 °C)[6] | ||
Solubility in ethanol | 20 °C, solution in ethanol: 1.2 mL/L (20% v/v)[7] | ||
Solubility in acetone | 20 °C, solution in acetone: 7.69 mL/L (38.46% v/v) 49.4 mL/L (62.5% v/v)[7] | ||
Solubility in diethylene glycol | 52 g/100 g (20 °C)[6] | ||
log P | 2.13 | ||
Vapor pressure | 12.7 kPa (25 °C) 24.4 kPa (40 °C) 181 kPa (100 °C)[8] | ||
Conjugate acid
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Benzenium[9]
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Conjugate base
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Benzenide[10] | ||
UV-vis (λmax) | 255 nm | ||
−54.8·10−6 cm3/mol | |||
Refractive index (nD)
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1.5011 (20 °C) 1.4948 (30 °C)[6] | ||
Viscosity | 0.7528 cP (10 °C) 0.6076 cP (25 °C) 0.4965 cP (40 °C) 0.3075 cP (80 °C) | ||
Structure | |||
Trigonal planar | |||
0 D | |||
Thermochemistry | |||
Heat capacity (C)
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134.8 J/mol·K | ||
Std molar
entropy (S⦵298) |
173.26 J/mol·K[8] | ||
Std enthalpy of (ΔfH⦵298)formation |
48.7 kJ/mol | ||
Std enthalpy of (ΔcH⦵298)combustion |
-3267.6 kJ/mol[8] | ||
Hazards | |||
Occupational safety and health (OHS/OSH): | |||
Main hazards
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potential occupational carcinogen, flammable | ||
GHS labelling: | |||
[11] | |||
Danger | |||
H225, H302, H304, H305, H315, H319, H340, H350, H372, H410[11] | |||
P201, P210, P301+P310, P305+P351+P338, P308+P313, P331[11] | |||
NFPA 704 (fire diamond) | |||
Flash point | −11.63 °C (11.07 °F; 261.52 K) | ||
497.78 °C (928.00 °F; 770.93 K) | |||
Explosive limits
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1.2–7.8% | ||
Lethal dose or concentration (LD, LC): | |||
LD50 (median dose)
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930 mg/kg (rat, oral)[13] | ||
LCLo (lowest published)
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44,000 ppm (rabbit, 30 min) 44,923 ppm (dog) 52,308 ppm (cat) 20,000 ppm (human, 5 min)[14] | ||
NIOSH (US health exposure limits): | |||
PEL (Permissible)
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TWA 1 ppm, ST 5 ppm[12] | ||
REL (Recommended)
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Ca TWA 0.1 ppm ST 1 ppm[12] | ||
IDLH (Immediate danger) |
500 ppm[12] | ||
Safety data sheet (SDS) | HMDB | ||
Related compounds | |||
Related compounds
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Toluene Borazine Divinylacetylene(isomer) Dewar benzene(isomer) | ||
Supplementary data page | |||
Benzene (data page) | |||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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.[15]
Benzene is a natural constituent of petroleum and is one of the elementary petrochemicals. Due to the cyclic continuous pi bonds between the carbon atoms, benzene is classed as an aromatic hydrocarbon. Benzene is a colorless and highly flammable liquid with a sweet smell, and is partially responsible for the aroma of gasoline. It is used primarily as a precursor to the manufacture of chemicals with more complex structures, such as ethylbenzene and cumene, of which billions of kilograms are produced annually. Although benzene is a major industrial chemical, it finds limited use in consumer items because of its toxicity. Benzene is a volatile organic compound.[16]
Benzene is classified as a carcinogen.[1]
History
Discovery
The word "benzene" derives from "gum benzoin" (benzoin resin), an aromatic resin known since ancient times in Southeast Asia, and later to European pharmacists and perfumers in the 16th century via trade routes.[17] An acidic material was derived from benzoin by sublimation, and named "flowers of benzoin", or benzoic acid. The hydrocarbon derived from benzoic acid thus acquired the name benzin, benzol, or benzene.[18] Michael Faraday first isolated and identified benzene in 1825 from the oily residue derived from the production of illuminating gas, giving it the name bicarburet of hydrogen.[19][20] In 1833, Eilhard Mitscherlich produced it by distilling benzoic acid (from gum benzoin) and lime. He gave the compound the name benzin.[21] In 1836, the French chemist Auguste Laurent named the substance "phène";[22] this word has become the root of the English word "phenol", which is hydroxylated benzene, and "phenyl", the radical formed by abstraction of a hydrogen atom from benzene.
In 1845, Charles Blachford Mansfield, working under August Wilhelm von Hofmann, isolated benzene from coal tar.[23] Four years later, Mansfield began the first industrial-scale production of benzene, based on the coal-tar method.[24][25] Gradually, the sense developed among chemists that a number of substances were chemically related to benzene, comprising a diverse chemical family. In 1855, Hofmann was the first to apply the word "aromatic" to designate this family relationship, after a characteristic property of many of its members.[26] In 1997, benzene was detected in deep space.[27]
Ring formula
Historic proposals of benzene structures | |||||
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By Adolf Karl Ludwig Claus (1867)[28] | By James Dewar (1869)[29] | By Albert Ladenburg (1869)[30] | |||
By August Kekulé (1865/1872)[31][32] | |||||
By Henry Edward Armstrong (1887)[33][34] | By Adolf von Baeyer (1888)[35] | By Friedrich Karl Johannes Thiele (1899)[36] |
The empirical formula for benzene was long known, but its highly polyunsaturated structure, with just one hydrogen atom for each carbon atom, was challenging to determine. Archibald Scott Couper in 1858 and Johann Josef Loschmidt in 1861[37] suggested possible structures that contained multiple double bonds or multiple rings, but in these years very little was known about aromatic chemistry, and so chemists were unable to adduce appropriate evidence to favor any particular formula.
But many chemists had begun to work on aromatic substances, especially in Germany, and relevant data was coming fast. In 1865, the German chemist
-
Kekulé's 1872 modification of his 1865 theory, illustrating rapid alternation of double bonds[note 1]
The new understanding of benzene, and hence of all aromatic compounds, proved to be so important for both pure and applied chemistry that in 1890 the German Chemical Society organized an elaborate appreciation in Kekulé's honor, celebrating the twenty-fifth anniversary of his first benzene paper. Here Kekulé spoke of the creation of the theory. He said that he had discovered the ring shape of the benzene molecule after having a reverie or day-dream of a snake biting its own tail (a symbol in ancient cultures known as the ouroboros).[40] This vision, he said, came to him after years of studying the nature of carbon-carbon bonds. This was seven years after he had solved the problem of how carbon atoms could bond to up to four other atoms at the same time. Curiously, a similar, humorous depiction of benzene had appeared in 1886 in a pamphlet entitled Berichte der Durstigen Chemischen Gesellschaft (Journal of the Thirsty Chemical Society), a parody of the Berichte der Deutschen Chemischen Gesellschaft, only the parody had monkeys seizing each other in a circle, rather than snakes as in Kekulé's anecdote.[41] Some historians have suggested that the parody was a lampoon of the snake anecdote, possibly already well known through oral transmission even if it had not yet appeared in print.[18] Kekulé's 1890 speech[42] in which this anecdote appeared has been translated into English.[43] If the anecdote is the memory of a real event, circumstances mentioned in the story suggest that it must have happened early in 1862.[44]
In 1929, the cyclic nature of benzene was finally confirmed by the
Nomenclature
The German chemist
Early applications
In 1903, Ludwig Roselius popularized the use of benzene to decaffeinate coffee. This discovery led to the production of Sanka. This process was later discontinued. Benzene was historically used as a significant component in many consumer products such as liquid wrench, several paint strippers, rubber cements, spot removers, and other products. Manufacture of some of these benzene-containing formulations ceased in about 1950, although Liquid Wrench continued to contain significant amounts of benzene until the late 1970s.[52]
Occurrence
Trace amounts of benzene are found in petroleum and coal. It is a byproduct of the incomplete combustion of many materials. For commercial use, until World War II, much of benzene was obtained as a by-product of coke production (or "coke-oven light oil") for the steel industry. However, in the 1950s, increased demand for benzene, especially from the growing polymers industry, necessitated the production of benzene from petroleum. Today, most benzene comes from the petrochemical industry, with only a small fraction being produced from coal.[53] Benzene has been detected on Mars.[54][55][56]
Structure
Derivatives of benzene occur sufficiently often as a component of organic molecules, so much so that the
Benzene derivatives
Many important chemical compounds are derived from benzene by replacing one or more of its hydrogen atoms with another functional group. Examples of simple benzene derivatives are phenol, toluene, and aniline, abbreviated PhOH, PhMe, and PhNH2, respectively. Linking benzene rings gives biphenyl, C6H5–C6H5. Further loss of hydrogen gives "fused" aromatic hydrocarbons, such as naphthalene, anthracene, phenanthrene, and pyrene. The limit of the fusion process is the hydrogen-free allotrope of carbon, graphite.
In
Production
Four chemical processes contribute to industrial benzene production:
Catalytic reforming
In catalytic reforming, a mixture of
In similar fashion to this catalytic reforming,
Toluene hydrodealkylation
Toluene hydrodealkylation converts toluene to benzene. In this hydrogen-intensive process, toluene is mixed with hydrogen, then passed over a chromium, molybdenum, or platinum oxide catalyst at 500–650 °C and 20–60 atm pressure. Sometimes, higher temperatures are used instead of a catalyst (at the similar reaction condition). Under these conditions, toluene undergoes dealkylation to benzene and methane:
This irreversible reaction is accompanied by an equilibrium side reaction that produces biphenyl (aka diphenyl) at higher temperature:
- 2 C
6H
6 ⇌ H
2 + C
6H
5–C
6H
5
If the raw material stream contains much non-aromatic components (paraffins or naphthenes), those are likely decomposed to lower hydrocarbons such as methane, which increases the consumption of hydrogen.
A typical reaction yield exceeds 95%. Sometimes, xylenes and heavier aromatics are used in place of toluene, with similar efficiency.
This is often called "on-purpose" methodology to produce benzene, compared to conventional BTX (benzene-toluene-xylene) extraction processes.
Toluene disproportionation
Toluene disproportionation (TDP) is the conversion of toluene to benzene and xylene.
Given that demand for para-xylene (p-xylene) substantially exceeds demand for other xylene isomers, a refinement of the TDP process called Selective TDP (STDP) may be used. In this process, the xylene stream exiting the TDP unit is approximately 90% p-xylene. In some systems, even the benzene-to-xylenes ratio is modified to favor xylenes.
Steam cracking
Steam cracking is the process for producing ethylene and other alkenes from aliphatic hydrocarbons. Depending on the feedstock used to produce the olefins, steam cracking can produce a benzene-rich liquid by-product called pyrolysis gasoline. Pyrolysis gasoline can be blended with other hydrocarbons as a gasoline additive, or routed through an extraction process to recover BTX aromatics (benzene, toluene and xylenes).
Other methods
Although of no commercial significance, many other routes to benzene exist.
Uses
Benzene is used mainly as an intermediate to make other chemicals, above all
Toluene is now often used as a substitute for benzene, for instance as a fuel additive. The solvent-properties of the two are similar, but toluene is less toxic and has a wider liquid range. Toluene is also processed into benzene.[68]
Component of gasoline
As a
In some European languages, the word for petroleum or gasoline is an exact cognate of "benzene". For instance in Catalan the word 'benzina' can be used for gasoline, though now it is relatively rare.
Reactions
The most common reactions of benzene involve substitution of a proton by other groups.
The most widely practiced example of this reaction is the
Approximately 24,700,000 tons were produced in 1999.
Sulfonation, chlorination, nitration
Using electrophilic aromatic substitution, many functional groups are introduced onto the benzene framework. Sulfonation of benzene involves the use of oleum, a mixture of sulfuric acid with sulfur trioxide. Sulfonated benzene derivatives are useful detergents. In nitration, benzene reacts with nitronium ions (NO2+), which is a strong electrophile produced by combining sulfuric and nitric acids. Nitrobenzene is the precursor to aniline. Chlorination is achieved with chlorine to give chlorobenzene in the presence of a Lewis acid catalyst such as aluminium tri-chloride.
Hydrogenation
Via
Metal complexes
Benzene is an excellent
Health effects
Benzene is classified as a carcinogen, which increases the risk of cancer and other illnesses, and is also a notorious cause of bone marrow failure. Substantial quantities of epidemiologic, clinical, and laboratory data link benzene to aplastic anemia, acute leukemia, bone marrow abnormalities and cardiovascular disease.[73][74][75] The specific hematologic malignancies that benzene is associated with include: acute myeloid leukemia (AML), aplastic anemia, myelodysplastic syndrome (MDS), acute lymphoblastic leukemia (ALL), and chronic myeloid leukemia (CML).[76]
The
As benzene is ubiquitous in gasoline and hydrocarbon fuels that are in use everywhere, human exposure to benzene is a global health problem. Benzene targets the liver, kidney, lung, heart and brain and can cause
Exposure to benzene
According to the
Exposure to benzene may lead progressively to aplastic
OSHA regulates levels of benzene in the workplace.[84] The maximum allowable amount of benzene in workroom air during an 8-hour workday, 40-hour workweek is 1 ppm. As benzene can cause cancer, NIOSH recommends that all workers wear special breathing equipment when they are likely to be exposed to benzene at levels exceeding the recommended (8-hour) exposure limit of 0.1 ppm.[85]
Benzene exposure limits
The
The U.S. Occupational Safety and Health Administration (OSHA) has set a permissible exposure limit of 1 part of benzene per million parts of air (1 ppm) in the workplace during an 8-hour workday, 40-hour workweek. The short term exposure limit for airborne benzene is 5 ppm for 15 minutes.[87] These legal limits were based on studies demonstrating compelling evidence of health risk to workers exposed to benzene. The risk from exposure to 1 ppm for a working lifetime has been estimated as 5 excess leukemia deaths per 1,000 employees exposed. (This estimate assumes no threshold for benzene's carcinogenic effects.) OSHA has also established an action level of 0.5 ppm to encourage even lower exposures in the workplace.[88]
The U.S.
American Conference of Governmental Industrial Hygienists (ACGIH) adopted Threshold Limit Values (TLVs) for benzene at 0.5 ppm TWA and 2.5 ppm STEL.[citation needed]
Toxicology
Biomarkers of exposure
Several tests can determine exposure to benzene. Benzene itself can be measured in breath, blood or urine, but such testing is usually limited to the first 24 hours post-exposure due to the relatively rapid removal of the chemical by exhalation or biotransformation. Most people in developed countries have measureable baseline levels of benzene and other aromatic petroleum hydrocarbons in their blood. In the body, benzene is enzymatically converted to a series of oxidation products including muconic acid, phenylmercapturic acid, phenol, catechol, hydroquinone and 1,2,4-trihydroxybenzene. Most of these metabolites have some value as biomarkers of human exposure, since they accumulate in the urine in proportion to the extent and duration of exposure, and they may still be present for some days after exposure has ceased. The current ACGIH biological exposure limits for occupational exposure are 500 μg/g creatinine for muconic acid and 25 μg/g creatinine for phenylmercapturic acid in an end-of-shift urine specimen.[92][93][94][95]
Biotransformations
Even if it is not a common substrate for metabolism, benzene can be oxidized by both
The pathway for the metabolism of benzene is complex and begins in the liver. Several enzymes are involved. These include
Genetic polymorphisms in these enzymes may induce loss of function or gain of function. For example, mutations in CYP2E1 increase activity and result in increased generation of toxic metabolites. NQ01 mutations result in loss of function and may result in decreased detoxification. Myeloperoxidase mutations result in loss of function and may result in decreased generation of toxic metabolites. GSH mutations or deletions result in loss of function and result in decreased detoxification. These genes may be targets for genetic screening for susceptibility to benzene toxicity.[97]
Molecular toxicology
The paradigm of toxicological assessment of benzene is shifting towards the domain of molecular toxicology as it allows understanding of fundamental biological mechanisms in a better way.
Biological oxidation and carcinogenic activity
One way of understanding the carcinogenic effects of benzene is by examining the products of biological oxidation. Pure benzene, for example, oxidizes in the body to produce an epoxide,
Routes of exposure
Inhalation
Outdoor air may contain low levels of benzene from automobile service stations, wood smoke, tobacco smoke, the transfer of gasoline, exhaust from motor vehicles, and industrial emissions.[101] About 50% of the entire nationwide (United States) exposure to benzene results from smoking tobacco or from exposure to tobacco smoke.[102] After smoking 32 cigarettes per day, the smoker would take in about 1.8 milligrams (mg) of benzene. This amount is about 10 times the average daily intake of benzene by nonsmokers.[103]
Inhaled benzene is primarily expelled unchanged through exhalation. In a human study 16.4 to 41.6% of retained benzene was eliminated through the lungs within five to seven hours after a two- to three-hour exposure to 47 to 110 ppm and only 0.07 to 0.2% of the remaining benzene was excreted unchanged in the urine. After exposure to 63 to 405 mg/m3 of benzene for 1 to 5 hours, 51 to 87% was excreted in the urine as phenol over a period of 23 to 50 hours. In another human study, 30% of absorbed dermally applied benzene, which is primarily metabolized in the liver, was excreted as phenol in the urine.[104]
Exposure from soft drinks
Under specific conditions and in the presence of other chemicals
Contamination of water supply
In 2005, the water supply to the city of
When plastic water pipes are subject to high heat, the water may be contaminated with benzene.[107]
Genocide
The Nazi German government used benzene administered via injection as one of their many methods for killing.[108][109]
See also
- BTEX
- 1,2,3-Cyclohexatriene
- Industrial Union Department v. American Petroleum Institute
- Six-membered aromatic rings with one carbon replaced by another element:
Explanatory notes
- ^ Critics pointed out a problem with Kekulé's original (1865) structure for benzene: Whenever benzene underwent substitution at the ortho position, two distinguishable isomers should have resulted, depending on whether a double bond or a single bond existed between the carbon atoms to which the substituents were attached; however, no such isomers were observed. In 1872, Kekulé suggested that benzene had two complementary structures and that these forms rapidly interconverted, so that if there were a double bond between any pair of carbon atoms at one instant, that double bond would become a single bond at the next instant (and vice versa). To provide a mechanism for the conversion process, Kekulé proposed that the valency of an atom is determined by the frequency with which it collided with its neighbors in a molecule. As the carbon atoms in the benzene ring collided with each other, each carbon atom would collide twice with one neighbor during a given interval and then twice with its other neighbor during the next interval. Thus, a double bond would exist with one neighbor during the first interval and with the other neighbor during the next interval. Therefore, between the carbon atoms of benzene there were no fixed (i.e., constant) and distinct single or double bonds; instead, the bonds between the carbon atoms were identical. See pages 86–89 Archived 2020-03-20 at the Wayback Machine of Auguste Kekulé (1872) "Ueber einige Condensationsprodukte des Aldehyds" (On some condensation products of aldehydes), Liebig's Annalen der Chemie und Pharmacie, 162(1): 77–124, 309–320. From p. 89: "Das einfachste Mittel aller Stöße eines Kohlenstoffatoms ergiebt sich aus der Summe der Stöße der beiden ersten Zeiteinheiten, die sich dann periodisch wiederholen. … man sieht daher, daß jedes Kohlenstoffatom mit den beiden anderen, … daß diese Verschiedenheit nur eine scheinbare, aber keine wirkliche ist." (The simplest average of all the collisions of a carbon atom [in benzene] comes from the sum of the collisions during the first two units of time, which then periodically repeat. … thus one sees that each carbon atom collides equally often with the two others against which it bumps, [and] thus stands in exactly the same relation with its two neighbors. The usual structural formula for benzene expresses, of course, only the collisions that occur during one unit of time, thus during one phase, and so one is led to the view [that] doubly substituted derivatives [of benzene] must be different at positions 1,2 and 1,6 [of the benzene ring]. If the idea [that was] just presented—or a similar one—can be regarded as correct, then [it] follows therefrom that this difference [between the bonds at positions 1,2 and 1,6] is only an apparent [one], not a real [one].)
References
- ^ ISBN 978-0-85404-182-4.
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- ISBN 978-0-7506-7766-0. Archivedfrom the original on 2016-03-12. Retrieved 2012-05-31.
- ^ a b c d e "Benzol". Archived from the original on 2014-05-29. Retrieved 2014-05-29.
- ^ a b Atherton Seidell; William F. Linke (1952). Solubilities of Inorganic and Organic Compounds: A Compilation of Solubility Data from the Periodical Literature. Supplement. Van Nostrand. Archived from the original on 2020-03-11. Retrieved 2015-06-27.
- ^ a b c Benzene in Linstrom, Peter J.; Mallard, William G. (eds.); NIST Chemistry WebBook, NIST Standard Reference Database Number 69, National Institute of Standards and Technology, Gaithersburg (MD) (retrieved 2014-05-29)
- ^ "Benzenium (CID 12533897". PubChem. February 8, 2007. Retrieved September 18, 2022.
- ^ "Benzenide (CID 5150480)". PubChem. June 24, 2005. Retrieved September 18, 2022.
- ^ a b c Sigma-Aldrich Co., Benzene Archived 2016-12-01 at the Wayback Machine. Retrieved on 2014-05-29.
- ^ a b c NIOSH Pocket Guide to Chemical Hazards. "#0049". National Institute for Occupational Safety and Health (NIOSH).
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- ^ "Benzene". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
- ISBN 9780080523781. Archivedfrom the original on 2021-02-08. Retrieved 2020-11-25 – via www.sciencedirect.com.
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- ^ .
- from the original on 2020-11-21. Retrieved 2012-01-15. On pages 443–450, Faraday discusses "bicarburet of hydrogen" (benzene). On pages 449–450, he shows that benzene's empirical formula is C6H6, although he doesn't realize it because he (like most chemists at that time) used the wrong atomic mass for carbon (6 instead of 12).
- .
- from the original on 2015-11-23. Retrieved 2015-06-27. In a footnote on page 43, Liebig, the journal's editor, suggested changing Mitscherlich's original name for benzene (namely, "benzin") to "benzol", because the suffix "-in" suggested that it was an alkaloid (e.g., Chinin (quinine)), which benzene isn't, whereas the suffix "-ol" suggested that it was oily, which benzene is. Thus on page 44, Mitscherlich states: "Da diese Flüssigkeit aus der Benzoësäure gewonnen wird, und wahrscheinlich mit den Benzoylverbindungen im Zusammenhang steht, so gibt man ihr am besten den Namen Benzol, da der Name Benzoïn schon für die mit dem Bittermandelöl isomerische Verbindung von Liebig und Wöhler gewählt worden ist." (Since this liquid [benzene] is obtained from benzoic acid and probably is related to benzoyl compounds, the best name for it is "benzol", since the name "benzoïn" has already been chosen, by Liebig and Wöhler, for the compound that's isomeric with the oil of bitter almonds [benzaldehyde].)
- ^ Laurent, (1836) "Sur la chlorophénise et les acides chlorophénisique et chlorophénèsique," Annales de Chemie et de Physique, vol. 63, pp. 27–45, see p. 44 Archived 2015-03-20 at the Wayback Machine: "Je donne le nom de phène au radical fondamental des acides précédens (φαινω, j'éclaire), puisque la benzine se trouve dans le gaz de l'éclairage." (I give the name of "phène" (φαινω, I illuminate) to the fundamental radical of the preceding acids, because benzene is found in illuminating gas.)
- from the original on 2015-11-22.
- from the original on 2015-10-27. Retrieved 2015-06-27.
- ^ Charles Mansfield filed for (November 11, 1847) and received (May 1848) a patent (no. 11,960) for the fractional distillation of coal tar.
- S2CID 97105342.
The existence and mode of formation of insolinic acid prove that to the series of monobasic aromatic acids, Cn2Hn2-8O4, the lowest known term of which is benzoic acid, … .
[Note: The empirical formulas of organic compounds that appear in Hofmann's article (p. 3) are based upon an atomic mass of carbon of 6 (instead of 12) and an atomic mass of oxygen of 8 (instead of 16).] - doi:10.1086/318871
- ^ Claus, Adolph K.L. (1867) "Theoretische Betrachtungen und deren Anwendungen zur Systematik der organischen Chemie" (Theoretical considerations and their applications to the classification scheme of organic chemistry), Berichte über die Verhandlungen der Naturforschenden Gesellschaft zu Freiburg im Breisgau (Reports of the Proceedings of the Scientific Society of Freiburg in Breisgau), 4 : 116–381. In the section Aromatischen Verbindungen (aromatic compounds), pp. 315–347, Claus presents Kekulé's hypothetical structure for benzene (p. 317), presents objections to it, presents an alternative geometry (p. 320), and concludes that his alternative is correct (p. 326). See also figures on p. 354 or p. 379.
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- ^ Kekulé, F. A. (1865). "Sur la constitution des substances aromatiques". Bulletin de la Société Chimique de Paris. 3: 98–110. Archivedfrom the original on 2015-11-14. Retrieved 2015-06-27. On p. 100, Kekulé suggests that the carbon atoms of benzene could form a "chaîne fermée" (closed chain).
- from the original on 2015-10-22. Retrieved 2015-06-27.
- ^ In his 1890 paper, Armstrong represented benzene nuclei within polycyclic benzenoids by placing inside the benzene nuclei a letter "C", an abbreviation of the word "centric". Centric affinities (i.e., bonds) acted within a designated cycle of carbon atoms. From p. 102: " … benzene, according to this view, may be represented by a double ring, in fact." See:
- Armstrong, H.E. (1890). "The structure of cycloid hydrocarbons". Proceedings of the Chemical Society. 6: 101–105. Archived from the original on 2021-11-16. Retrieved 2018-02-17.
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External links
- Benzene at The Periodic Table of Videos(University of Nottingham)
- International Chemical Safety Card 0015
- USEPA Summary of Benzene Toxicity
- NIOSH Pocket Guide to Chemical Hazards
- Benzene from PubChem
- Dept. of Health and Human Services: TR-289: Toxicology and Carcinogenesis Studies of Benzene
- Video Podcast of Sir John Cadogan giving a lecture on Benzene since Faraday, in 1991
- Substance profile
- NLM Hazardous Substances Databank – Benzene