Benzene
IUPAC name	Benzene
Other names	Benzol
Identifiers
CAS number	[71-43-2]
PubChem	241
RTECS number	CY1400000
SMILES	c1ccccc1 C1=CC=CC=C1
Properties
Molecular formula	C6H6
Molar mass	78. IUPAC Nomenclature is a system of naming Chemical compounds and of describing the science of Chemistry in general CAS registry numbers are unique numerical identifiers for Chemical compounds Polymers biological sequences mixtures and Alloys They are also referred to PubChem is a Database of chemical Molecules The system is maintained by the National Center for Biotechnology Information (NCBI a component Registry of Toxic Effects of Chemical Substances ( RTECS) is a Database of Toxicity information compiled from the open scientific literature without reference A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes Molar mass, symbol M, is the Mass of one mole of a substance ( Chemical element or Chemical compound) 1121 g/mol
Appearance	Colorless liquid
Density	0. The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different 8786 g/cm³, liquid
Melting point	5. The melting point of a solid is the temperature range at which it changes state from solid to Liquid. 5 °C (278. 6 K)
Boiling point	80. The boiling point of a liquid is the temperature at which the Vapor pressure of the liquid equals the environmental pressure surrounding the liquid 1 °C (353. 2 K)
Solubility in water	0. Solubility is the characteristic Physical property referring to the ability of a given substance the Solute, to dissolve in a Solvent. Water is a common Chemical substance that is essential for the survival of all known forms of Life. 8 g/L (25 °C)
Viscosity	0. Viscosity is a measure of the resistance of a Fluid which is being deformed by either Shear stress or Extensional stress. 652 cP at 20 °C
Dipole moment	0 D
Hazards
MSDS	External MSDS
EU classification	(F) Carc. Cat. 1 Muta. Cat. 2 Toxic (T)
NFPA 704	4 3 0
R-phrases	R45, R46, R11, R36/38,R48/23/24/25, R65
S-phrases	S53, S45
Flash point	−11 °C
Related compounds
Related compounds	toluene borazine
Supplementary data page
Structure and properties	n, εr, etc. The poise (symbol P pwɑːz is the unit of dynamic Viscosity in the Centimetre gram second system of units. In physics there are two kinds of dipoles ( Hellènic: di(s- = two- and pòla = pivot hinge An electric dipole is a The debye (symbol D) is a non- SI, CGS unit of electrical dipole moment. A material safety data sheet ( MSDS) is a form containing data regarding the properties of a particular substance This page provides supplementary chemical data on Benzene Council Directive 67/548/EEC of 27 June 1967 on the approximation of laws regulations and administrative provisions relating to the classification packaging and labelling The term carcinogen refers to any substance Radionuclide or radiation that is an agent directly involved in the promotion of Cancer or in the fatation of its propagation In Biology, a mutagen ( Latin, literally origin of change) is a physical or chemical agent that changes the genetic information (usually DNA) Symbolism The four divisions are typically color-coded with blue indicating level of Health Hazard, red indicating R-phrases (short for Risk Phrases) are defined in Annex III of European Union Directive 67/548/EEC: Nature of special risks attributed to dangerous R-phrases (short for Risk Phrases) are defined in Annex III of European Union Directive 67/548/EEC: Nature of special risks attributed to dangerous R-phrases (short for Risk Phrases) are defined in Annex III of European Union Directive 67/548/EEC: Nature of special risks attributed to dangerous R-phrases (short for Risk Phrases) are defined in Annex III of European Union Directive 67/548/EEC: Nature of special risks attributed to dangerous R-phrases (short for Risk Phrases) are defined in Annex III of European Union Directive 67/548/EEC: Nature of special risks attributed to dangerous R-phrases (short for Risk Phrases) are defined in Annex III of European Union Directive 67/548/EEC: Nature of special risks attributed to dangerous R-phrases (short for Risk Phrases) are defined in Annex III of European Union Directive 67/548/EEC: Nature of special risks attributed to dangerous S-phrases are defined in Annex IV of European Union Directive 67/548/EEC: Safety advice concerning dangerous substances and preparations. S-phrases are defined in Annex IV of European Union Directive 67/548/EEC: Safety advice concerning dangerous substances and preparations. S-phrases are defined in Annex IV of European Union Directive 67/548/EEC: Safety advice concerning dangerous substances and preparations. The flash point of a flammable liquid is the lowest Temperature at which it can form an ignitable mixture in air Toluene, also known as methylbenzene or phenylmethane, is a clear water -insoluble liquid with the typical smell of Paint thinners redolent of Borazine is an Inorganic compound composed of the elements Boron, Nitrogen and Hydrogen. This page provides supplementary chemical data on Benzene This page provides supplementary chemical data on Benzene The refractive index (or index of Refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves is reduced inside the medium Measurement The relative static permittivity εr can be measured for static Electric fields as follows first the Capacitance of a test
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Benzene, or benzol, is an organic chemical compound and a known carcinogen with the molecular formula C₆H₆. This page provides supplementary chemical data on Benzene This page provides supplementary chemical data on Benzene Ultraviolet-visible spectroscopy or ultraviolet-visible spectrophotometry ( UV/ VIS) involves the Spectroscopy of Photons in the UV-visible Infrared spectroscopy (IR spectroscopy is the subset of Spectroscopy that deals with the Infrared region of the Electromagnetic spectrum. Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy, is the name given to a technique which exploits the magnetic properties of certain nuclei Mass spectrometry is an analytical technique that identifies the chemical composition of a compound or sample based on the Mass-to-charge ratio of charged particles In Chemistry, the standard state of a material is its state at 1 bar (100 Kilopascals exactly An organic compound is any member of a large class of Chemical compounds whose Molecules contain Carbon. A chemical compound is a substance consisting of two or more different elements chemically bonded together in a fixed proportion by Mass. The term carcinogen refers to any substance Radionuclide or radiation that is an agent directly involved in the promotion of Cancer or in the fatation of its propagation Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 It is sometimes abbreviated Ph–H. In Organic chemistry, the phenyl group or phenyl ring (often abbreviated as -Ph) is the Functional group with the formula - Benzene is a colorless and highly flammable liquid with a sweet smell and a relatively high melting point. Flammability is the ease with which a substance will ignite causing Fire or Combustion. Because of this, its use as an additive in gasoline is now limited, but it is an important industrial solvent and precursor in the production of drugs, plastics, synthetic rubber, and dyes. A solvent is a liquid or gas that dissolves a solid liquid or gaseous Solute, resulting in a Solution. Medication, also referred to as medicine, can be loosely defined as any substance intended for use in the diagnosis cure mitigation treatment or prevention of disease Plastic is the general common term for a wide range of synthetic or semisynthetic organic solid materials suitable for the manufacture of industrial products A dye can generally be described as a Colored substance that has an affinity to the substrate to which it is being applied Benzene is a natural constituent of crude oil, but it is usually synthesized from other compounds present in petroleum. Petroleum ( L petroleum, from Greek πετρέλαιον, lit Benzene is an aromatic hydrocarbon and the second [n]-annulene ([6]-annulene), a cyclic hydrocarbon with a continuous pi bond. Annulenes are completely conjugated monocyclic Hydrocarbons They have the general formula CnHn (n is an even number or CnHn+1 In Chemistry, pi bonds ( π bonds) are covalent Chemical bonds where two lobes of one involved electron orbital overlap two lobes

Contents 1 History 1.1 Discovery 1.2 Ring formula 2 Structure 3 Substituted benzene derivatives 4 Production 4.1 Catalytic reforming 4.2 Toluene hydrodealkylation 4.3 Toluene disproportionation 4.4 Steam cracking 5 Uses 5.1 Early uses 5.2 Current uses of benzene 6 Reactions of benzene 7 Health effects 7.1 Biological oxidation and carcinogenic activity 8 References 9 External links

History

Discovery

The word "benzene" derives historically from "gum benzoin", sometimes called "benjamin" (i. e. , benzoin resin), an aromatic resin known to European pharmacists and perfumers since the 15th century as a product of southeast Asia. Benzoin resin or styrax resin is a Balsamic Resin obtained from the bark of several species of trees in the genus Styrax. "Benzoin" is itself a corruption of the Arabic expression "luban jawi," or "frankincense of Java. " 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. ^[1]

Benzene has been the subject of many studies by scientists ranging from Michael Faraday to Linus Pauling. Michael Faraday, FRS ( September 22 1791 – August 25 1867) was an English Linus Carl Pauling (February 28 1901 – August 19 1994 was an American Scientist, Peace activist, Author and educator. 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. ^[2][3] In 1833, Eilhard Mitscherlich produced it via the distillation of benzoic acid (from gum benzoin) and lime. Eilhard Mitscherlich (7 January 1794 &ndash 28 August 1863 was a German Chemist, who is perhaps best remembered today for his law of isomorphism (1819 which states Distillation is a method of separating Mixtures based on differences in their volatilities in a boiling liquid mixture Benzoic acid, C7H6O2 (or C6H5COOH is a colorless crystalline solid and the simplest Aromatic Carboxylic acid Benzoin resin or styrax resin is a Balsamic Resin obtained from the bark of several species of trees in the genus Styrax. Calcium oxide ( CaO) commonly known as burnt lime, lime or quicklime, is a widely used Chemical compound. Mitscherlich gave the compound the name benzin. ^[4] In 1836 the French chemist Auguste Laurent named the substance "phène"; this is the root of the word phenol, which is hydroxylated benzene, and phenyl, which is the radical formed by abstraction of a hydrogen atom from benzene. Auguste Laurent ( November 14, 1807 - April 23, 1853) was a French Chemist who discovered Anthracene, Phthalic Phenol, is a toxic colourless Crystalline Solid with a sweet tarry odor commonly referred to as a "hospital smell" In Organic chemistry, the phenyl group or phenyl ring (often abbreviated as -Ph) is the Functional group with the formula -

In 1845, Charles Mansfield, working under August Wilhelm von Hofmann, isolated benzene from coal tar. August Wilhelm von Hofmann ( April 8, 1818 &ndash May 5, 1892) was a German Chemist. Coal tar is a brown or black liquid of high Viscosity, which smells of Naphthalene and Aromatic hydrocarbons Coal tar is among the by-products when coal Four years later, Mansfield began the first industrial-scale production of benzene, based on the coal-tar method.

Gradually the sense developed among chemists that substances related to benzene formed a natural chemical family. In 1855 August Wilhelm Hofmann used the word "aromatic" to designate this family relationship, after a characteristic property of many of its members. August Wilhelm von Hofmann ( April 8, 1818 &ndash May 5, 1892) was a German Chemist.

Ring formula

The empirical formula for benzene was long known, but its highly polyunsaturated structure was challenging to determine. In Chemistry, saturation has five different meanings In Physical chemistry, saturation is the point at which a Solution of a substance Archibald Scott Couper in 1858 and Joseph Loschmidt in 1861 suggested possible structures that contained multiple double bonds or multiple rings, but the study of aromatic compounds was in its very early years, and too little evidence was then available to help chemists decide on any particular structure. Archibald Scott Couper (31 March 1831 &ndash 11 March 1892 was a Scottish chemist who proposed an early theory of chemical structure and bonding Jan or Johann Josef Loschmidt ( March 15 1821 - July 8 1895) who referred to himself mostly as 'Josef' (omitting his first name

In 1865 the German chemist Friedrich August Kekulé published a paper in French (for he was then teaching in Francophone Belgium) suggesting that the structure contained a six-membered ring of carbon atoms with alternating single and double bonds. Friedrich August Kekule von Stradonitz (also August Kekulé) (7 September 1829 &ndash 13 July 1896 was a German organic chemist. The next year he published a much longer paper in German on the same subject. ^[5][6] Kekulé used evidence that had accumulated in the intervening years—namely, that there always appeared to be only one isomer of any monoderivative of benzene, and that there always appeared to be exactly three isomers of every diderivative—to argue in support of his proposed structure. This article is about the chemical concept For "isomerism" of atomic nuclei see Nuclear isomer. In Chemistry, a derivative is a compound that is formed from a similar compound or a compound that can be imagined to arise from another compound if one Kekulé's symmetrical ring could explain these curious facts.

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 seizing its own tail (this is a common symbol in many ancient cultures known as the Ouroboros). The Ouroboros (Greek grc Ουροβόρος from grc ουροβόρος όφις "tail-devouring snake" also spelled Ourorboros, Oroborus, Uroboros This vision, he said, came to him after years of studying the nature of carbon-carbon bonds. This was 20 years after he had solved the problem of how carbon atoms could bond to up to four other atoms at the same time. It is curious that a similar humorous depiction of benzene had appeared in 1886 in the 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. ^[7] 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. ^[1] Others have speculated that Kekulé's story in 1890 was a re-parody of the monkey spoof, and was a mere invention rather than a recollection of an event in his life.

Kekulé's 1890 speech^[8] in which these anecdotes appeared has been translated into English. ^[9] If one takes the anecdote as the memory of a real event, circumstances mentioned in the story suggest that it must have happened early in 1862. ^[10]

The cyclic nature of benzene was finally confirmed by the crystallographer Kathleen Lonsdale. Dame Kathleen Lonsdale (née Yardley ( 28 January 1903 - 1 April 1971) was a crystallographer, who established the structure of ^[11][12]

Structure

Main article: Aromaticity

Benzene represents a special problem in that, to account for all the bonds, there must be alternating double carbon bonds:^[13]

Using X-ray diffraction, researchers discovered that all of the carbon-carbon bonds in benzene are of the same length of 140 picometres (pm). X-ray scattering techniques are a family of non-destructive analytical techniques which reveal information about the crystallographic structure chemical composition A picometre ( American spelling: picometer, symbol pm) is a unit of Length in the Metric system, equal to one trillionth The C–C bond lengths are greater than a double bond (135pm) but shorter than a single bond (147pm). In Molecular geometry, bond length or bond distance is the average distance between nuclei of two bonded Atoms in a Molecule. This intermediate distance is explained by electron delocalization: the electrons for C–C bonding are distributed equally between each of the six carbon atoms. In chemistry delocalized electrons are Electrons in a Molecule that are not associated with a single Atom or to a Covalent bond. One representation is that the structure exists as a superposition of so-called resonance structures, rather than either form individually. Resonance in Chemistry is a theory used to represent and model certain types of non-classical Molecular structures Resonance is a key component This delocalisation of electrons is known as aromaticity, and gives benzene great stability. This enhanced stability is the fundamental property of aromatic molecules that differentiates them from molecules that are non-aromatic. To reflect the delocalised nature of the bonding, benzene is often depicted with a circle inside a hexagonal arrangement of carbon atoms:

As is common in organic chemistry, the carbon atoms in the diagram above have been left unlabeled. Realising each carbon has 2p electrons, each carbon donates 1p electron into the delocalised ring above and below the benzene ring. It is the side-on overlap of p-orbitals that produces the pi clouds.

Benzene occurs sufficiently often as a component of organic molecules that there is a Unicode symbol with the code U+232C (⌬) to represent it with three double bonds, and U+23E3 (⏣) for a delocalized version. In Computing, Unicode is an Industry standard allowing Computers to consistently represent and manipulate text expressed in most of the world's ^[14]

Substituted benzene derivatives

Main article: Aromatic hydrocarbons

Many important chemicals are derived from benzene, wherein with one or more of the hydrogen atoms is replaced with another functional group. In Organic chemistry, functional groups are specific groups of Atoms within Molecules that are responsible for the characteristic Chemical reactions Examples of simple benzene derivatives are phenol, toluene, and aniline, abbreviated PhOH, PhMe, and PhNH₂, respectively. Phenol, is a toxic colourless Crystalline Solid with a sweet tarry odor commonly referred to as a "hospital smell" Toluene, also known as methylbenzene or phenylmethane, is a clear water -insoluble liquid with the typical smell of Paint thinners redolent of Aniline, phenylamine or aminobenzene is an Organic compound with the formula C6H7N Linking benzene rings gives biphenyl, C₆H₅–C₆H₅. Biphenyl (or diphenyl or phenyl benzene or 11'-biphenyl or lemonene) is a solid Organic compound that forms colorless to yellowish crystals Further loss of hydrogen gives "fused" aromatic hydrocarbons, such as naphthalene and anthracene. Naphthalene, also known as naphthalin, naphthaline, tar camphor, white tar, albocarbon, or antimite and not to be Anthracene is a solid Polycyclic aromatic hydrocarbon consisting of three fused Benzene rings derived from Coal-tar. The limit of the fusion process is the hydrogen-free material graphite. The Mineral graphite, as with Diamond and Fullerene, is one of the Allotropes of carbon.

In heterocycles, carbon atoms in the benzene ring are replaced with other elements. The most important derivatives are the rings containing nitrogen. Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Replacing one CH with N gives the compound pyridine, C₅H₅N. Pyridine is a Chemical compound with the formula C5[[Hydrogen H5]] N. Although benzene and pyridine are structurally related, benzene cannot be converted into pyridine. Replacement of a second CH bond with N gives, depending on the location of the second N, pyridazine, pyrimidine, and pyrazine. Pyridazine is a heteroaromatic Organic compound with the molecular formula C4H4N2 sometimes called 12- Diazine. Pyrimidine is a Heterocyclic Aromatic Organic compound similar to Benzene and Pyridine, containing two Nitrogen Atoms Pyrazine is a Heterocyclic Aromatic Organic compound. Pyrazine is a symmetrical molecule with Point group D2h

Production

Trace amounts of benzene may result whenever carbon-rich materials undergo incomplete combustion. Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Combustion or burning is a complex sequence of Exothermic chemical reactions between a Fuel and an Oxidant accompanied by the production of It is produced in volcanoes and forest fires, and is also a component of cigarette smoke. Plate tectonics and hotspots Divergent plate boundaries At the A wildfire, also known as a wildland fire, forest fire, brush fire, vegetation fire, grass fire, Peat fire, A cigarette ( French "small Cigar " from cigar + -ette) is a product consumed through Smoking and manufactured

Up until World War II, most benzene was produced as a byproduct of coke production (or "coke-oven light oil") in the steel industry. World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including Coke is a solid Carbonaceous material derived from Destructive distillation of low-ash low-sulfur Bituminous coal. Steel is an Alloy consisting mostly of Iron, with a Carbon content between 0 However, in the 1950s, increased demand for benzene, especially from the growing plastics industry, necessitated the production of benzene from petroleum. Plastic is the general common term for a wide range of synthetic or semisynthetic organic solid materials suitable for the manufacture of industrial products Today, most benzene comes from the petrochemical industry, with only a small fraction being produced from coal. Petrochemicals are chemical products made from raw materials of Petroleum or other Hydrocarbon origin

Four chemical processes contribute to industrial benzene production: catalytic reforming, toluene hydrodealkylation, toluene disproportionation, and steam cracking. Catalytic reforming is a chemical process used to convert Petroleum refinery Naphthas typically having low octane ratings, into high-octane liquid products Toluene, also known as methylbenzene or phenylmethane, is a clear water -insoluble liquid with the typical smell of Paint thinners redolent of In Petroleum geology and Chemistry, cracking is the process whereby complex organic Molecules such as Kerogens or heavy Hydrocarbons In the US, 50% of benzene comes from catalytic reforming and 25% from steam cracking. Catalytic reforming is a chemical process used to convert Petroleum refinery Naphthas typically having low octane ratings, into high-octane liquid products In Petroleum geology and Chemistry, cracking is the process whereby complex organic Molecules such as Kerogens or heavy Hydrocarbons In Western Europe, 50% of benzene comes from steam cracking and 25% from catalytic reforming. In Petroleum geology and Chemistry, cracking is the process whereby complex organic Molecules such as Kerogens or heavy Hydrocarbons Catalytic reforming is a chemical process used to convert Petroleum refinery Naphthas typically having low octane ratings, into high-octane liquid products

Catalytic reforming

In catalytic reforming, a mixture of hydrocarbons with boiling points between 60–200 °C is blended with hydrogen gas and then exposed to a bifunctional platinum chloride or rhenium chloride catalyst at 500–525 °C and pressures ranging from 8–50 atm. In Organic chemistry, a hydrocarbon is an Organic compound consisting entirely of Hydrogen and Carbon. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Platinum (ˈplætɪnəm is a Chemical element with the Atomic symbol Pt and an Atomic number of 78 Rhenium (ˈriːniəm is a Chemical element with the symbol Re and Atomic number 75 Catalysis is the process in which the rate of a Chemical reaction is increased by means of a Chemical substance known as a catalyst Under these conditions, aliphatic hydrocarbons form rings and lose hydrogen to become aromatic hydrocarbons. In Organic chemistry, compounds composed of Carbon and Hydrogen are divided into two classes Aromatic compounds which contain Benzene rings The aromatic products of the reaction are then separated from the reaction mixture (or reformate) by extraction with any one of a number of solvents, including diethylene glycol or sulfolane, and benzene is then separated from the other aromatics by distillation. Liquid-liquid extraction, also known as solvent extraction and partitioning, is a method to separate compounds based on their relative solubilities in two A solvent is a liquid or gas that dissolves a solid liquid or gaseous Solute, resulting in a Solution. Diethylene glycol (DEG is an Organic compound described by the structural formula HO-CH2-CH2-O-CH2-CH2-OH Sulfolane (also tetramethylene sulfone, systematic name: 2345-tetrahydrothiophene-11-dioxide) is a clear colorless Liquid commonly The extraction step of aromatics from the reformate is designed to produce aromatics with lowest non-aromatic components. So-called "BTX (Benzene-Toluene-Xylenes)" process consists of such extraction and distillation steps.

Similarly to this catalytic reforming, UOP and BP commercialized a method from LPG (mainly propane and butane) to aromatics. BP plc, previously known as British Petroleum, is the third largest global Energy company, a multinational oil company (" Oil major

Toluene hydrodealkylation

Toluene hydrodealkylation converts toluene to benzene. Toluene, also known as methylbenzene or phenylmethane, is a clear water -insoluble liquid with the typical smell of Paint thinners redolent of In this hydrogen-intensive process, toluene is mixed with hydrogen, then passed over a chromium, molybdenum, or platinum oxide catalyst at 500–600 °C and 40–60 atm pressure. Chromium (ˈkroʊmiəm is a Chemical element which has the symbol Cr and Atomic number 24 Molybdenum (məˈlɪbdənəm from the Greek word for the metal " Lead " is a Group 6 Chemical element with the symbol Mo Platinum (ˈplætɪnəm is a Chemical element with the Atomic symbol Pt and an Atomic number of 78 An oxide is a Chemical compound containing at least one Oxygen atom as well as at least one other element Sometimes, higher temperatures are used instead of a catalyst (at the similar reaction condition). Under these conditions, toluene undergoes dealkylation according to the chemical equation:

C₆H₅CH₃ + H₂ → C₆H₆ + CH₄

This irreversible reaction is accompanied by an equilibrium side reaction that produces biphenyl (aka diphenyl) at higher temperature: 2 C₆H₆ ↔ H₂ + C₁₂H₁₀

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 chemical equation is a symbolic representation of a Chemical reaction. Toluene, also known as methylbenzene or phenylmethane, is a clear water -insoluble liquid with the typical smell of Paint thinners redolent of Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. Biphenyl (or diphenyl or phenyl benzene or 11'-biphenyl or lemonene) is a solid Organic compound that forms colorless to yellowish crystals

A typical reaction yield exceeds 95%. Sometimes, xylenes and heavier aromatics are used in place of toluene, with similar efficiency. o-Xylene|m-Xylene|p-XyleneThe term xylene or xylol refers to a mixture of three Benzene derivatives which is used as a Solvent in the Printing

This is often called "on-purpose" methodology to produce benzene, compared to conventional BTX (benzene-toluene-xylene) processes. The hydrodealkylation process is not economically feasible if the price gap between benzene and toluene is small (or the gap is smaller than about 15% of benzene price).

Toluene disproportionation

Where a chemical complex has similar demands for both benzene and xylene, then toluene disproportionation (TDP) may be an attractive alternative to the toluene hydrodealkylation. o-Xylene|m-Xylene|p-XyleneThe term xylene or xylol refers to a mixture of three Benzene derivatives which is used as a Solvent in the Printing Disproportionation or dismutation is used to describe two particular types of chemical reaction A chemical reaction of the type 2A → A' + A" where Broadly speaking 2 toluene molecules are reacted and the methyl groups rearranged from one toluene molecule to the other, yielding one benzene molecule and one xylene molecule.

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. p -Xylene is an Aromatic hydrocarbon, based on Benzene with two Methyl Substituents The “p” stands for para, identifying In this process, the xylene stream exiting the TDP unit is approximately 90% paraxylene. In some current catalytic systems, even the benzene-to-xylenes ratio is decreased (more xylenes) when the demand of xylenes is higher.

Steam cracking

Steam cracking is the process for producing ethylene and other alkenes from aliphatic hydrocarbons. In Petroleum geology and Chemistry, cracking is the process whereby complex organic Molecules such as Kerogens or heavy Hydrocarbons Structure This Hydrocarbon has four Hydrogen Atoms bound to a pair of Carbon atoms that are connected by a Double bond. In Organic chemistry, an alkene, olefin, or olefine is an unsaturated Chemical compound containing at least one Carbon In Organic chemistry, compounds composed of Carbon and Hydrogen are divided into two classes Aromatic compounds which contain Benzene rings Depending on the feedstock used to produce the olefins, steam cracking can produce a benzene-rich liquid byproduct called pyrolysis gasoline. Pyrolysis gasoline can be blended with other hydrocarbons as a gasoline additive, or distilled (in BTX process) to separate it into its components, including benzene.

Uses

Early uses

In the 19th and early-20th centuries, benzene was used as an after-shave lotion because of its pleasant smell. Prior to the 1920s, benzene was frequently used as an industrial solvent, especially for degreasing metal. As its toxicity became obvious, benzene was supplanted by other solvents, especially toluene (methyl benzene), which has similar physical properties but is not as carcinogenic. Toluene, also known as methylbenzene or phenylmethane, is a clear water -insoluble liquid with the typical smell of Paint thinners redolent of

In 1903, Ludwig Roselius popularized the use of benzene to decaffeinate coffee. This discovery led to the production of Sanka (the letters "ka" in the brand name stand for kaffein). Sanka is a brand of decaffeinated Coffee, sold around the world and was one of the earliest decaffeinated varieties This process was later discontinued.

As a petrol additive, benzene increases the octane rating and reduces knocking. The octane rating is a measure of the resistance of Gasoline and other Fuels to Detonation ( Engine knocking) in spark-ignition Knocking (also called knock, detonation or spark knock, pinking in UK English or pinging in US English in spark-ignition Consequently, petrol often contained several percent benzene before the 1950s, when tetraethyl lead replaced it as the most widely-used antiknock additive. Tetra-ethyl lead, abbreviated TEL, is an organometallic compound with the formula ( CH3CH2)4 Pb. With the global phaseout of leaded petrol, benzene has made a comeback as a gasoline additive in some nations. In the United States, concern over its negative health effects and the possibility of benzene entering the groundwater have led to stringent regulation of petrol's benzene content, with limits typically around 1%. The United States of America —commonly referred to as the Groundwater is Water located beneath the Ground surface in Soil pore spaces and in the Fractures of lithologic formations European petrol specifications now contain the same 1% limit on benzene content. The US EPA has new regulations that will lower the benzene content in gasoline to 0. 62% in 2011. ^[15]

Current uses of benzene

Today benzene is mainly used as an intermediate to make other chemicals. Its most widely-produced derivatives include styrene, which is used to make polymers and plastics, phenol for resins and adhesives (via cumene), and cyclohexane, which is used in the manufacture of Nylon. Styrene, also known as vinyl benzene as well as many other names (see table is an Organic compound with the Chemical formula C6H5CH=CH2 Phenol, is a toxic colourless Crystalline Solid with a sweet tarry odor commonly referred to as a "hospital smell" Cumene is the common name for isopropylbenzene, an Organic compound that is an Aromatic Hydrocarbon. Cyclohexane is a Cycloalkane with the Molecular formula C 6 H 12 Smaller amounts of benzene are used to make some types of rubbers, lubricants, dyes, detergents, drugs, explosives, napalm and pesticides. A lubricant (sometimes referred to as a "Lube" is a substance (often a liquid introduced between two moving surfaces to reduce the Friction between them improving A dye can generally be described as a Colored substance that has an affinity to the substrate to which it is being applied A detergent (as a noun is a material intended to assist Cleaning. A drug, broadly speaking is any chemical substance that when absorbed into the body An explosive material is a material that either is chemically or otherwise Energetically unstable or produces a sudden expansion of the material usually accompanied Napalm is the name given to any of a number of Flammable Liquids used in Warfare often jellied Gasoline. A pesticide is a substance or mixture of substances used to kill a pest.

In both US and Europe, 50% of benzene is used in the production of ethylbenzene / styrene, 20% is used in the production of cumene, and about 15% of benzene is used in the production of cyclohexane (eventually to nylon). Ethylbenzene is an Organic compound with the formula C6H5CH2CH3 Cumene is the common name for isopropylbenzene, an Organic compound that is an Aromatic Hydrocarbon. Cyclohexane is a Cycloalkane with the Molecular formula C 6 H 12 Overview Nylon is a Thermoplastic silky material first used commercially in a nylon- Bristled Toothbrush (1938 followed more famously by

In laboratory research, toluene is now often used as a substitute for benzene. Toluene, also known as methylbenzene or phenylmethane, is a clear water -insoluble liquid with the typical smell of Paint thinners redolent of The solvent-properties of the two are similar but toluene is less toxic and has a wider liquid range.

Benzene has been used as a basic research tool in a variety of experiments including analysis of a two-dimensional gas. A two-dimensional gas is a collection of N objects which are constrained to move in a planar or other two- Dimensional space in a Gaseous state It can also be found in tobacco smoke. Tobacco Smoking is the inhalation of smoke from burned dried or cured leaves of the Tobacco plant most often in the form of a Cigarette.

Reactions of benzene

• Electrophilic aromatic substitution is a general method of derivatizing benzene. Electrophilic aromatic substitution or EAS is an Organic reaction in which an atom usually Hydrogen, appended to an aromatic system is replaced Benzene is sufficiently nucleophilic that it undergoes substitution by acylium ions or alkyl carbocations to give substituted derivatives. In Chemistry, a nucleophile (literally nucleus lover as in nucleus and phile) is a Reagent that forms a Chemical bond to acyl group ( IUPAC name alkanoyl) is a Functional group derived by the removal of one or more Hydroxyl group from an Oxoacid. A carbocation (ˌkɑrboʊˈkætaɪɒn is an Ion with a positively-charged Carbon Atom.

• • The Friedel-Crafts acylation is a specific example of electrophilic aromatic substitution. The Friedel-Crafts reactions are a set of reactions developed by Charles Friedel and James Crafts in 1877. Electrophilic aromatic substitution or EAS is an Organic reaction in which an atom usually Hydrogen, appended to an aromatic system is replaced The reaction involves the acylation of benzene (or many other aromatic rings) with an acyl chloride using a strong Lewis acid catalyst such as aluminium chloride or iron chloride which act as a halogen carrier. In Chemistry, acylation (rarely but more formally alkanoylation) is the process of adding an Acyl group to a compound In Organic chemistry, an acyl chloride (or acid chloride) is an Organic compound which is a reactive derivative of a Carboxylic acid. Catalysis is the process in which the rate of a Chemical reaction is increased by means of a Chemical substance known as a catalyst Aluminium chloride (AlCl3 is a compound of Aluminium and Chlorine.

• • Like the Friedel-Crafts acylation, the Friedel-Crafts alkylation involves the alkylation of benzene (and many other aromatic rings) using an alkyl halide in the presence of a strong Lewis acid catalyst. The Friedel-Crafts reactions are a set of reactions developed by Charles Friedel and James Crafts in 1877. Alkylation is the transfer of an Alkyl group from one Molecule to another The haloalkanes (also known as halogenoalkanes or alkyl halides) are a group of Chemical compounds consisting of Alkanes such as Methane
  • sulfonation. Aromatic sulfonation is an Organic reaction in which a hydrogen atom on an arene is replaced by a Sulfonic acid Functional group in an Electrophilic
  • Nitration: Benzene undergoes nitration with nitronium ions (NO₂⁺) as the electrophile. Nitration is a general Chemical process for the introduction of a nitro group into a Chemical compound. Thus, warming benzene at 50-55 degrees Celsius, with a combination of concentrated sulfuric and nitric acid to produce the electrophile, gives nitrobenzene.
• Hydrogenation(Reduction): Benzene and derivatives convert to cyclohexane and derivatives when treated with hydrogen at 450 K and 10 atm of pressure with a finely divided nickel catalyst. Hydrogenation is the Chemical reaction that results in addition of Hydrogen (H2 Nickel (ˈnɪkəl is a metallic Chemical element with the symbol Ni and Atomic number 28 Catalysis is the process in which the rate of a Chemical reaction is increased by means of a Chemical substance known as a catalyst
• Benzene is an excellent ligand in the organometallic chemistry of low-valent metals. The term complex in Chemistry is usually used to describe molecules or ensembles formed by the combination of Ligands and metal Ions. Important examples include the sandwich and half-sandwich complexes respectively Cr(C₆H₆)₂ and [RuCl₂(C₆H₆)]₂. Bis(benzenechromium is the Chemical compound with the formula Cr( η6 -C6H62

Health effects

Benzene exposure has serious health effects. Health effects, health impacts or health risks are changes in Health resulting from exposure to a source Outdoor air may contain low levels of benzene from tobacco smoke, automobile service stations, exhaust from motor vehicles, and industrial emissions. ^[16] Vapors from products that contain benzene, such as glues, paints, furniture wax, and detergents, can also be a source of exposure. Air around hazardous waste sites or gas stations will contain higher levels of benzene.

Breathing high levels of benzene can result in death, while low levels can cause drowsiness, dizziness, rapid heart rate, headaches, tremors, confusion, and unconsciousness. Death is the termination of the biological functions that define living Organisms It refers both to a specific A headache ( cephalalgia in medical terminology is a condition of pain in the Head; sometimes Neck or upper back pain may also be interpreted Tremor is an unintentional somewhat rhythmic muscle movement involving to-and-from movements (oscillations of one or more parts of the body Eating or drinking foods containing high levels of benzene can cause vomiting, irritation of the stomach, dizziness, sleepiness, convulsions, and death. In Human anatomy, the stomach is a J-shaped hollow muscular organ of the Gastrointestinal tract involved in the second phase of Digestion, following

The major effects of benzene are chronic (long-term) exposure through the blood. In Medicine, a chronic disease is a Disease that is long-lasting or recurrent Blood is a specialized Bodily fluid that delivers necessary substances to the body's cells ��such as nutrients and oxygen—and transports Waste products Benzene damages the bone marrow and can cause a decrease in red blood cells, leading to anemia. Bone marrow is the flexible tissue found in the hollow interior of Bones In adults marrow in large bones produces new Blood cells It constitutes 4% of Anemia ( AmE) or anæmia/anaemia ( BrE) (from the Ancient Greek grc-Latn anaîmia, meaning “without blood” is defined as a qualitative It can also cause excessive bleeding and depress the immune system, increasing the chance of infection. An immune system is a collection of mechanisms within an Organism that protects against Disease by identifying and killing Pathogens and Tumor An infection is the detrimental Colonization of a host Organism by a foreign Species.

Human exposure to benzene is a global health problem. Benzene targets liver, kidney, lung, heart and the brain and can cause DNA strand breaks, chromosomal damage etc. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known A chromosome is an organized structure of DNA and Protein that is found in cells. Benzene causes cancer in both animals and humans. Cancer (medical term Malignant Neoplasm) is a class of Diseases in which a group of cells display uncontrolled Benzene was first reported to induce cancer in humans in the 1920s. It wasn't until 1979 that the cancer inducing properties were determined conclusively in humans. Industry exploited this "discrepancy" and tried to discredit animal studies which showed benzene caused cancer saying that they weren't relevant to humans. Benzene has been shown to cause cancer in both sexes of multiple species of laboratory animals exposed via various routes. ^[17][18]

Some women who breathed high levels of benzene for many months had irregular menstrual periods and a decrease in the size of their ovaries. See also "Mensuration" a term sometimes used to describe Measurement, particularly in the context of Forestry. "Ovaria" redirects here This is also a proposed section and a Synonym of Solanum. It is not known whether benzene exposure affects the developing fetus in pregnant women or fertility in men. A fetus (or foetus or fœtus) is a developing Mammal or other Viviparous Vertebrate, after the Embryonic stage and

Animal studies have shown low birth weights, delayed bone formation, and bone marrow damage when pregnant animals breathed benzene.

Benzene has been connected to a rare form of kidney cancer in two separate studies, one involving tank truck drivers, and the other involving seamen on tanker vessels, both carrying benzene laden chemicals.

The US Department of Health and Human Services (DHHS) classifies benzene as a human carcinogen. The United States Department of Health and Human Services ( HHS) is a Cabinet department of the United States government with the goal of protecting The term carcinogen refers to any substance Radionuclide or radiation that is an agent directly involved in the promotion of Cancer or in the fatation of its propagation Long-term exposure to high levels of benzene in the air can cause leukemia, a potentially fatal cancer of the blood-forming organs. Leukemia or leukaemia (Greek leukos λευκός, "white" aima αίμα, "blood" is a Cancer of the Blood Cancer (medical term Malignant Neoplasm) is a class of Diseases in which a group of cells display uncontrolled In particular, Acute myeloid leukemia or acute non-lymphocytic leukaemia (AML & ANLL) may be caused by benzene. Acute myeloid leukemia ( AML) also known as acute myelogenous leukemia, is a Cancer of the Myeloid line of White blood cells characterized

Several tests can determine exposure to benzene. There is a test for measuring benzene in the breath; this test must be done shortly after exposure. Benzene can also be measured in the blood; however, because benzene disappears rapidly from the blood, measurements are accurate only for recent exposures.

In the body, benzene is metabolized. Metabolism is the set of Chemical reactions that occur in living Organisms in order to maintain Life. Certain metabolites, such as trans,trans-muconic acid can be measured in the urine. Muconic acid is a dicarboxylic acid There are three Isomeric forms designated transtrans -muconic acid cistrans -muconic acid and ciscis Urine is a liquid waste product of the body secreted by the Kidneys by a process of filtration from Blood and Excreted through the Urethra. However, this test must be done shortly after exposure and is not a reliable indicator of benzene exposure, since the same metabolites may be present in urine from other sources.

The United States Environmental Protection Agency has set the maximum permissible level of benzene in drinking water at 0. 005 milligrams per liter (0. 005 mg/L). The EPA requires that spills or accidental releases into the environment of 10 pounds (4. 5 kg) or more of benzene be reported to the EPA.

The US Occupational Safety and Health Administration (OSHA) has set a permissible exposure limit of 0. The United States Occupational Safety and Health Administration (OSHA is an agency of the United States Department of Labor. 5 part of benzene per million parts of air (. 5 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.

In recent history there have been many examples of the harmful health effects of benzene and its derivatives. Toxic Oil Syndrome caused localised immune-suppression in Madrid in 1981 from people ingesting anilide-contaminated rapeseed oil. Toxic Oil Syndrome or simply Toxic Syndrome was the name given to an unusual Disease outbreak in Spain in 1981. Madrid (pronounced in English in Spanish and colloquially in Spain) is the Capital and largest city of Spain. Aniline, phenylamine or aminobenzene is an Organic compound with the formula C6H7N Rapeseed ( Brassica napus) also known as rape, oilseed rape, rapa, rapaseed and (in the case of one particular group of Chronic Fatigue Syndrome has also been correlated with people who eat "denatured" food that use solvents to remove fat or contain benzoic acid but causality is unproven. Chronic fatigue syndrome ( CFS) is the most common name given to a poorly understood variably debilitating disorder or disorders of uncertain causation Benzoic acid, C7H6O2 (or C6H5COOH is a colorless crystalline solid and the simplest Aromatic Carboxylic acid

Workers in various industries that make or use benzene may be at risk for being exposed to high levels of this carcinogenic chemical. Industries that involve the use of benzene include the rubber industry, oil refineries, chemical plants, shoe manufacturers, and gasoline related industries. In 1987, OSHA estimated that about 237,000 workers in the United States were potentially exposed to benzene, and it is not known if this number has substantially changed since then. The United States Occupational Safety and Health Administration (OSHA is an agency of the United States Department of Labor.

Water and soil contamination are important pathways of concern for transmission of benzene contact. Soil contamination is caused by the presence of man-made chemicals or other alteration in the natural soil environment In the U. S. alone there are approximately 100,000 different sites which have benzene soil or groundwater contamination. In 2005, the water supply to the city of Harbin in China with a population of almost nine million people, was cut off because of a major benzene exposure. ( Russian Kharbin) is a Sub-provincial city and the Capital of the Heilongjiang Province in Northeast China. The Jilin chemical plant explosions were a series of explosions which occurred on November 13 2005, in the No Benzene leaked into the Songhua River, which supplies drinking water to the city, after an explosion at a China National Petroleum Corporation (CNPC) factory in the city of Jilin on 13 November. The Songhua River (also known as the Sungari River in English a name which comes from the Manchu language meaning White River) is a River in Events 1002 - English king Ethelred orders the killing of all Danes in England, known today as the St

In March 2006, the official Food Standards Agency in Britain conducted a survey of 150 brands of soft drinks. The Food Standards Agency is a Non-ministerial government department of the Government of the United Kingdom. The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located It found that four contained benzene levels above World Health Organization limits. The affected batches were removed from sale. See benzene in soft drinks^[19]

Biological oxidation and carcinogenic activity

One way of understanding the carcinogenic effects of benzene is by examining the products of biological oxidation. Benzene in soft drinks is the occurrence of the Carcinogenic (cancer-causing chemical Benzene in certain Soft drinks This contamination is a Public Pure benzene, for example, oxidizes in the body to produce an epoxide, benzene oxide, which is not excreted readily and can interact with DNA to produce harmful mutations.

References

External links

• Benzene
• Benzene Material Safety Data Sheet
• International Chemical Safety Card 0015
• USEPA Summary of Benzene Toxicity
• MSAT Regulations and Remedies
• Australian National Pollutant Inventory - Benzene
• NIOSH Pocket Guide to Chemical Hazards
• IARC Monograph: "Benzene"
• CID 241 from PubChem
• Computational Chemistry Wiki
• Couper and Carbon bonds
• Dept. of Health and Human Services: TR-289: Toxicology and Carcinogenesis Studies of Benzene
• Kekule, Couper and dreams of Benzene
• Loschmidt's Benzene structure
• Video Podcast (Sir John Cadogan giving a lecture on Benzene since Faraday, in 1991)
• Benzene 3D view and pdb-file
• National Institute for Occupational Safety and Health - Benzene Page
• Substance profile

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