Benzene
Chemical name	Benzene
Chemical formula	C6H6
Molecular mass	78.11 g/mol
Density	0.8786 g/ml
Melting point	5.5 °C
Boiling point	80.1 °C
Heat of vaporization	44.3 kJ/mol
Heat of fusion	9.84 kJ/mol
CAS number	71-43-2
SMILES	C1=CC=CC=C1

Benzene, C₆H₆, PhH, or benzol is a colorless and flammable liquid with a pleasant, sweet smell. Benzene is a carcinogen. It is a component of gasoline and of napalm. It is an important industrial solvent and precursor in the production of drugs, plastics, gasoline, synthetic rubber, and dyes. Benzene is a natural constituent of crude oil, but it is usually synthesized from other compounds present in petroleum. Benzene is an aromatic hydrocarbon, and the second [n]-annulene ([6]-annulene). IUPAC nomenclature is a systematic way of naming organic chemical compounds as recommended by the International Union of Pure and Applied Chemistry (IUPAC). ... A chemical formula (also called molecular formula) is a concise way of expressing information about the atoms that constitute a particular chemical compound. ... The molecular mass of a substance (less accurately called molecular weight and abbreviated as MW) is the mass of one molecule of that substance, relative to the unified atomic mass unit u (equal to 1/12 the mass of one atom of carbon-12). ... Density (symbol: ρ - Greek: rho) is a measure of mass per unit of volume. ... The melting point of a solid is the temperature at which it changes state from solid to liquid. ... The boiling point of a substance is the temperature at which it can change state from a liquid to a gas throughout the bulk of the liquid. ... The heat of vaporization is a physical property of substances. ... This article is in need of attention. ... CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences, mixtures and alloys. ... The simplified molecular input line entry specification or SMILES is a specification for unambiguously describing the structure of chemical molecules using short ASCII alpha-numeric strings. ... Chemical structure of benzene Selfmade by cacycle File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... General Name, Symbol, Number Carbon, C, 6 Chemical series Nonmetals Group, Period, Block 14 (IVA), 2, p Density, Hardness 2267 kg/m3 0. ... General Name, Symbol, Number Hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1 (IA), 1, s Density, Hardness 0. ... In chemistry, a phenyl-group is a hydrophobic aromatic functional group which is derived from benzene (C6H6). ... Color is an important part of the visual arts. ... For other uses see fire (disambiguation). ... In pathology, a carcinogen is any substance or agent that promotes cancer. ... Petrol pumps in Germany Petrol (commonly known as gasoline in North America, and sometimes also called motor spirit) is a petroleum-derived liquid mixture consisting primarily of hydrocarbons, used as fuel in internal combustion engines. ... A napalm airstrike during the Vietnam War Napalm is a flammable, gasoline-based weapon invented in 1942. ... A solvent is a liquid that dissolves a solid, liquid, or gaseous solute, resulting in a solution. ... Many drugs are provided in tablet form. ... The term plastics covers a range of synthetic or semi-synthetic polymerization products. ... Rubber is an elastic hydrocarbon polymer which occurs as a milky emulsion (known as latex) in the sap of a number of plants but can also be produced synthetically. ... A dye can generally be described as a coloured substance that has an affinity to the substrate to which it is being applied. ... Nodding donkey pumping an oil well near Sarnia, Ontario, 2001 Petroleum (from Latin petra – rock and oleum – oil), crude oil, sometimes colloquially called black gold, is a thick, dark brown or greenish flammable liquid, which exists in the upper strata of some areas of the Earths crust. ... An aromatic hydrocarbon (abbreviated as AH), or arene is a hydrocarbon, the molecular structure of which incorporates one or more planar sets of six carbon atoms that are connected by delocalised electrons numbering the same as if they consisted of alternating single and double covalent bonds. ... Annulenes are completely conjugated monocyclic hydrocarbons. ...

History

Benzene was discovered in 1825 by the English scientist Michael Faraday, who isolated it from oil gas and gave it the name bicarburet of hydrogen. In 1833, the German chemist Eilhard Mitscherlich produced it via the distillation of benzoic acid (from gum benzoin) and lime. Mitscherlich gave the compound the name benzin. In 1845, the English chemist Charles Mansfield, working under August Wilhelm von Hofmann, isolated benzene from coal tar. Four years later, Mansfield began the first industrial-scale production of benzene, based on the coal-tar method. 1825 was a common year starting on Saturday (see link for calendar). ... Royal motto: Dieu et mon droit (French: God and my right) Englands location within the UK Official language English de facto Capital London de facto Largest city London Area  - Total Ranked 1st UK 130,395 km² Population  - Total (2001)  - Density Ranked 1st UK 49,138,831 377/km² Religion... Michael Faraday Michael Faraday (September 22, 1791 – August 25, 1867) was a British scientist (a physicist and chemist) who contributed significantly to the fields of electromagnetism and electrochemistry. ... 1833 was a common year starting on Tuesday (see link for calendar). ... Strathisla whisky distillery in Keith, Scotland Distillation is a means of separating liquids through differences in their boiling points. ... Structural formula Benzoic acid, C8H5C(O)OH, is an aromatic carboxylic acid. ... Commonly called benzoin, it is called benzoin resin here to distinguish it from the crystalline compound benzoin. ... Calcium oxide (CaO), commonly known as lime, quicklime or burnt lime, is a widely used chemical compound. ... 1845 was a common year starting on Wednesday (see link for calendar). ... August Wilhelm von Hofmann (April 8, 1818 _ May 5, 1892) was a German chemist. ... Coal tar is the liquid by-product of the distillation of coal to make coke. ...

Structure

The formula of benzene (C₆H₆), caused a mystery for some time after its discovery, as no proposed structure could take account of all the bonds (carbon usually forms four single bonds and hydrogen one). General Name, Symbol, Number Carbon, C, 6 Chemical series Nonmetals Group, Period, Block 14 (IVA), 2, p Density, Hardness 2267 kg/m3 0. ...

The chemist Friedrich August Kekulé von Stradonitz was the first to deduce the ring structure of benzene. After years of studying carbon bonding, benzene and related molecules, he dreamt one night of a snake eating its own tail. (See Ouroboros.) Upon waking he was inspired to deduce the ring structure of benzene. A chemist is a scientist who specializes in chemistry. ... Kekulé von Stradonitz Friedrich August Kekulé von Stradonitz ( September 7, 1829 – July 13, 1896) was a German organic chemist. ... The Ouroboros Alternate spellings: Oroborus, Uroboros, Uroborus The Ouroboros is an ancient symbol depicting a snake or dragon swallowing its tail, constantly creating itself and forming a circle. ...

While his claims were well publicized and accepted, by the early 1920s Kekulé's biographer came to the conclusion that Kekulé's understanding of the tetravalent nature of carbon bonding depended on the previous research of Archibald Scott Couper (1831-1892); further, the German chemist Josef Loschmidt (1821-1895) had earlier posited a cyclic structure for benzene as early as 1862. The cyclic nature of benzene was finally confirmed by the eminent crystallographer Kathleen Lonsdale. Archibald Scott Couper (1831-1892) was the author of On a New Chemical Theory, Philosophical Magazine 16, 104-116 (1858) [as excerpted in Alembic Club Reprint #21, On a New Chemical Theory and Researches on Salicylic Acid[1]] Friedrich August Kekulé von Stradonitz claimed to solve the structure of Benzene... 1831 was a common year starting on Saturday (see link for calendar). ... 1892 was a leap year starting on Friday (see link for calendar). ... Johann Josef Loschmidt (March 15, 1821 - July 8, 1895) was an Austrian physicist and chemist. ... 1821 was a common year starting on Monday (see link for calendar). ... 1895 was a common year starting on Tuesday (see link for calendar). ... 1862 - Wikipedia /**/ @import /skins/monobook/IE50Fixes. ... Kathleen Lonsdale (January 23, 1901 - 1971) was a prominent crystallographer. ...

Benzene presents a special problem in that, to account for all the bonds, there must be alternating double carbon bonds:

Chemical structure of benzene Selfmade by cacycle File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...

Using X-ray diffraction, researchers discovered that all of the carbon-carbon bonds in benzene are of the same length, and it is known that a single bond is longer than a double bond. In addition, the bond length (the distance between the two bonded atoms) in benzene is greater than a double bond, but shorter than a single bond. There seems in effect to be a bond and a half between each carbon. X-ray crystallography is a technique in crystallography in which the pattern produced by the diffraction of x-rays through the closely spaced lattice of atoms in a crystal is recorded and then analyzed to reveal the nature of that lattice. ...

This is explained by electron delocalization. In order to picture this, we must consider the position of electrons in the bonds of benzene. In chemistry, delocalized electrons are electrons in a molecule that do not belong to a single atom or a covalent bond. ...

One representation is that the structure exists as a superposition of the forms below, rather than either form individually. This type of structure is called a resonance hybrid.

Chemical structure of benzene Selfmade by cacycle File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...

In reality, neither form really exists. Delocalisation must be explained using a higher level of theory than single and double bonds. The single bonds are formed with electrons in line between the carbon atoms - this is called σ (sigma) symmetry. Double bonds consist of a sigma bond and another, π (pi) bond. This second bond has electrons orbiting in paths above and below the plane of the ring at each bonded carbon atom. The π-bonds are formed from atomic p-orbitals above and below the plane of ring. The following diagram shows the positions of these p-orbitals: An atomic orbital is the description of the behavior of an electron in an atom according to quantum mechanics. ...

Orbitals in benzene. ...

Since they are out of the plane of the atoms, these orbitals can interact with each other freely, and become delocalised. This means that instead of being tied to one atom of carbon, each electron is shared by all six in the ring. Thus there are not enough electrons to form double bonds on all the carbon atoms, but the "extra" electrons strengthen all of the bonds on the ring equally. The resulting molecular orbital has π symmetry. In quantum chemistry, molecular orbitals are the statistical states electrons can have within molecules. ...

Benzene orbitals, cropped and translated from de:Bild:Benzol. ...

This delocalisation of electrons is known as aromaticity, and gives benzene great stability. This is the fundamental property of aromatic chemicals which differentiates them from non aromatics. In chemistry, an aromatic molecule is one in which electrons are free to cycle around circular arrangements of atoms, which are alternately singly and doubly bonded to one another. ...

To reflect the delocalised nature of the bonding, benzene may be depicted as a circle inside a hexagon in chemical structure diagrams:

Chemical structure of benzene Selfmade by cacycle Old version: File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...

As is common in diagrams of molecular structures, the carbon atoms in the diagram above have been left unlabeled.

Benzene occurs sufficiently often as a component of organic molecules that there is a Unicode symbol with the code 232C to represent it: ⌬ In computing, Unicode is the international standard whose goal is to provide the means to encode the text of every document people want to store in computers. ...

Note: Many fonts do not have this Unicode character, so your browser may not be able to display it correctly.

Substituted benzenes

Many important chemicals are essentially benzene, with one or more of the hydrogen atoms replaced with another functional group: In ecology functional groups are collections of organisms based on morphological, physiological, behavioral, biochemical, or environmental responses or on trophic criteria. ...

Alkyl substituents (aklylbenzenes)

• toluene C₆H₅-CH₃
• xylene C₆H₄(-CH₃)₂
• mesitylene C₆H₃(-CH₃)₃

Toluene, also known as methylbenzene or phenylmethane is a clear water-insoluble liquid with the typical smell of paint thinners, reminiscent of the sweet smell of the related compound benzene. ... The term xylenes refers to a group of 3 benzene derivatives which encompasses ortho-, meta-, and para- isomers of dimethyl benzene. ... In organic chemistry, mesitylene or 1,3,5-trimethylbenzene (C9H12) is an aromatic hydrocarbon with three methyl substituents attached to the benzene ring. ...

Other substituents

• phenol C₆H₅-OH
• aniline C₆H₅-NH₂
• chlorobenzene C₆H₅-Cl
• nitrobenzene C₆H₅-NO₂
• picric acid C₆H₂(-OH)(-NO₂)₃
• trinitrotoluene C₆H₂(-CH₃)(-NO₂)₃
• benzoic acid C₆H₅-COOH
• salicylic acid C₆H₄(-OH)(-COOH)
• acetylsalicylic acid C₆H₄(-O-C(=O)-CH₃)(-COOH)
• paracetamol C₆H₄(-NH-C(=O)-CH₃)(-OH)
• phenacetin C₆H₄(-NH-C(=O)-CH₃)(-O-CH₂-CH₃)

Phenol, also known under the old name carbolic acid, is a colorless crystalline solid with a typical sweet tarry odor. ... Aniline, phenylamine or aminobenzene (C6H5NH2) is an organic chemical compound which is a primary aromatic amine consisting of a benzene ring and an amino group. ... Chlorobenzene is a toxic aromatic compound, with the chemical formula C6H5Cl. ... Chemical structure of nitrobenzene Nitrobenzene, also known as nitrobenzol or oil of mirbane, is a poisonous organic compound with an almond odor and chemical formula C6H5NO2. ... Picric acid is the common term for the chemical compound 2,4,6-trinitrophenol; the material is a yellow crystalline solid. ... Trinitrotoluene (TNT) is a pale yellow crystalline aromatic hydrocarbon compound that melts at 354 K (178 °F, 81 °C). ... Structural formula Benzoic acid, C8H5C(O)OH, is an aromatic carboxylic acid. ... Salicylic acid is a colorless, crystalline organic carboxylic acid. ... A very old bottle of Aspirin Aspirin or acetylsalicylic acid is a drug in the family of salicylates, often used as an analgesic (against minor pains and aches), antipyretic (against fever), and anti-inflammatory. ... Paracetamol (INN) or acetaminophen (USAN) (popular brand name Tylenol), is a popular analgesic and antipyretic drug that is used for the relief of fever, headaches, and other minor aches and pains. ... Categories: Stub | Analgesics | Antipyretics | Sedatives ...

Fused aromatic rings

• naphthalene
• anthracene
• phenanthrene
• indole
• benzofuran
• quinoline
• isoquinoline
• polycyclic aromatic hydrocarbons (PAH)

Naphthalene (also known as naphthalin, naphthaline, tar camphor, white tar, albocarbon, or naphthene) is a crystalline white solid hydrocarbon with a typical mothball odor. ... In chemistry, anthracene is a solid polycyclic aromatic hydrocarbon consisting of three benzene rings derived from coal-tar. ... Phenanthrene is a polycyclic aromatic hydrocarbon composed of three fused benzene rings--as the above formula shows. ... Indole is an aromatic heterocyclic organic compound. ... Benzofuran, also known as Cumaron, Coumarone, or benzo[b]furan, is a heterocyclic aromatic organic compound. ... Quinoline, also known as 1-azanaphthalene, 1-benzazine, or benzo[b]pyridine, is a heterocyclic aromatic organic compound. ... Isoquinoline is a heterocyclic aromatic organic compound. ... Polycyclic aromatic hydrocarbons, also known as PAH, are chemical compounds that consist of fused aromatic rings and that do not contain heteroatoms and that do not carry substituents. ...

Heterocyclic analogs

In heterocycles, carbon atoms in the benzene ring are replaced with another element: Heterocyclic compounds are substances which contain a ring structure as found in benzene and the aromatic compounds, or aromatic hydrocarbons, but in which other atoms than carbon, such as sulfur, oxygen or nitrogen are found as part of the ring. ...

• pyridine
• pyrazine
• pyrimidine
• pyridazine

Pyridine is a clear liquid with an odor that is sour, putrid, and fish-like. ... Pyrazine is a heterocyclic aromatic organic compound. ... Pyrimidine is a heterocyclic aromatic organic compound, which is similar to benzene and pyridine and that contains two nitrogen atoms at positions 1 and 3 of the six-membered ring. ...

Production

Benzene may result whenever carbon-rich materials undergo incomplete combustion. It is produced naturally in volcanoes and forest fires, and is also a component of cigarette smoke. General Name, Symbol, Number Carbon, C, 6 Chemical series Nonmetals Group, Period, Block 14 (IVA), 2, p Density, Hardness 2267 kg/m3 0. ... Combustion or burning is an exothermic reaction between a substance (the fuel) and a gas (the oxidizer) to release heat. ... A volcano is a geological landform (usually a mountain) where magma (rock of the earths interior made molten or liquid by high pressure and temperature) erupts through the surface of the planet. ... Fire in San Bernardino, California Mountains (image taken from the International Space Station) A wildfire, also known as a forest fire, vegetation fire, grass fire, or bushfire (in Australasia), is an uncontrolled fire in wildland often caused by lightning; other common causes are human carelessness and arson. ... A cigarette will burn to ash on one end. ...

Up until World War II, most benzene was produced as a byproduct of coke production in the steel industry. However, in the 1950s, increased demand for benzene, especially from the growing plastics 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. Mushroom cloud from the nuclear explosion over Nagasaki rising 18 km into the air. ... Coke is a solid carbonaceous residue derived from low-ash, low-sulfur bituminous coal from which the volatile constituents (including water, coal-gas and coal-tar) are driven off by baking in an airless oven at temperatures as high as 1,000 degrees Celsius so that the fixed carbon and... Steel framework Steel is a metal alloy whose major component is iron, with carbon being the primary alloying material. ... Millennia: 1st millennium - 2nd millennium - 3rd millennium Events and trends Technology United States tests the first fusion bomb. ... The term plastics covers a range of synthetic or semi-synthetic polymerization products. ... A petrochemical is any chemical derived from fossil fuel. ...

Three chemical processes contribute about equally to industrial benzene production: catalytic reforming, toluene hydrodealkylation, and steam cracking. A catalytic reforming process converts a feed stream containing paraffins and naphthenes into aromatics to be used either as a motor fuel, such as gasoline or as a source for specific aromatic compounds for use in petrochemicals production. ... Toluene, also known as methylbenzene or phenylmethane is a clear water-insoluble liquid with the typical smell of paint thinners, reminiscent of the sweet smell of the related compound benzene. ... In petroleum geology and chemistry, cracking is the process whereby complex organic molecules (e. ...

Catalytic reforming

In catalytic reforming, a mixture of hydrocarbons with boiling points between 60-200°C is blended with hydrogen gas, then exposed to a platinum chloride or rhenium chloride catalyst at 500-525°C and pressures ranging from 8-50 atm. Under these conditions, aliphatic hydrocarbons form rings and lose hydrogen to become aromatic hydrocarbons. The aromatic products of the reaction are then separated from the reaction mixture 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. In chemistry, a hydrocarbon is any chemical compounds that consists only of carbon (C) and hydrogen (H). ... General Name, Symbol, Number Hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1 (IA), 1, s Density, Hardness 0. ... General Name, Symbol, Number Platinum, Pt, 78 Chemical series transition metals Group, Period, Block 10 , 6, d Density, Hardness 21. ... General Name, Symbol, Number Rhenium, Re, 75 Chemical series transition metals Group, Period, Block 7 (VIIB), 6, d Density, Hardness 21020 kg/m3, 7 Appearance grayish white Atomic properties Atomic weight 186. ... A catalyst (Greek: καταλύτης, catalytis) is a substance that accelerates the rate of a chemical reaction, at some temperature, but without itself being transformed or consumed by the reaction (see also catalysis). ... In chemistry, non-aromatic organic compounds are called aliphatic. ... In chemistry, liquid-liquid extraction is a useful method to separate components (compounds) of a mixture. ... A solvent is a liquid that dissolves a solid, liquid, or gaseous solute, resulting in a solution. ...

Toluene hydrodealkylation

Toluene hydrodealkylation converts toluene to benzene. In this 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. Sometimes, higher temperatures are used instead of a catalyst. Under these conditions, toluene undergoes dealkylation according to the chemical equation: General Name, Symbol, Number chromium, Cr, 24 Chemical series transition metals Group, Period, Block 6 (VIB), 4, d Appearance silvery metallic Atomic properties Atomic weight 51. ... General Name, Symbol, Number molybdenum, Mo, 42 Chemical series transition metal Group, Period, Block 6 (VIB), 5, d Density, Hardness 10280 kg/m3, 5. ... General Name, Symbol, Number Platinum, Pt, 78 Chemical series transition metals Group, Period, Block 10 , 6, d Density, Hardness 21. ... An oxide is a chemical compound of oxygen with other chemical elements, e. ... In chemistry, a chemical equation is a symbolic representation of a chemical reaction. ...

C₆H₅CH₃ + H₂ → C₆H₆ + CH₄

Typical reaction yields exceed 95%. Sometimes, xylene and heavier aromatics are used in place of toluene, with similar efficiency. Toluene, also known as methylbenzene or phenylmethane is a clear water-insoluble liquid with the typical smell of paint thinners, reminiscent of the sweet smell of the related compound benzene. ... General Name, Symbol, Number Hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1 (IA), 1, s Density, Hardness 0. ... The simplest hydrocarbon, methane, is a gas with a chemical formula of CH4. ... The term xylenes refers to a group of 3 benzene derivatives which encompasses ortho-, meta-, and para- isomers of dimethyl benzene. ...

Steam cracking

Steam cracking is the process used to produce ethylene and other olefins from aliphatic hydrocarbons. 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 to separate it into its components, including benzene. In petroleum geology and chemistry, cracking is the process whereby complex organic molecules (e. ... Ethylene or ethene is the simplest alkene hydrocarbon, consisting of two carbon atoms and four hydrogens. ... An olefin is an alkene hydrocarbon. ...

Uses

Prior to the 1920's, benzene was frequently used as an industrial solvent, especially for degreasing metal. As its toxicity became obvious, other solvents replaced benzene in applications that directly exposed the user to benzene.

As a gasoline additive, benzene increases the octane rating and reduces knocking. As a result, gasoline often contained several percent benzene before the 1950s, when tetraethyl lead replaced it as the most widely used antiknock additive. However, with the global phaseout of leaded gasoline, 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 gasoline's benzene content, with values around 1% typical. European gasoline specifications now contain the same 1% limit on benzene content. Petrol pumps in Germany Petrol (commonly known as gasoline in North America, and sometimes also called motor spirit) is a petroleum-derived liquid mixture consisting primarily of hydrocarbons, used as fuel in internal combustion engines. ... Knocking (also called pinking or pinging)—technically detonation— in internal combustion engines occurs when fuel in the cylinder is ignited by the firing of the spark plug but burns too quickly, combusting completely before the optimum moment during the compression phase of the four-stroke cycle. ... Tetra-ethyl lead (also known as TEL, lead tetraethyl and tetraethyllead) is a toxic organometallic chemical compound, with formula (CH2CH3)4Pb, which was once used as a gasoline (petrol) additive. ... Groundwater is water flowing within aquifers below the water table. ...

By far the largest use of benzene is an intermediate to make other chemicals. The most widely produced derivatives of benzene are styrene, which is used to make polymers and plastics, phenol for resins and adhesives (via cumene), and cyclohexane, which is used in Nylon manufacture. Smaller amounts of benzene are used to make some types of rubbers, lubricants, dyes, detergents, drugs, explosives and pesticides. Chemical Structure of Styrene Styrene (also vinyl benzene, ethenylbenzene, phenethylene, cinnamene, diarex HF 77, styrolene, styrol, styropol) is an organic compound which is an aromatic hydrocarbon having the chemical formula C8H8. ... Phenol, also known under the old name carbolic acid, is a colorless crystalline solid with a typical sweet tarry odor. ... A cyclohexane molecule in chair conformation, with hydrogen atoms in axial position in red, equatorial in blue. ...

Health effects

Breathing very high levels of benzene can result in death, while high levels can cause drowsiness, dizziness, rapid heart rate, headaches, tremors, confusion, and unconsciousness. Eating or drinking foods containing high levels of benzene can cause vomiting, irritation of the stomach, dizziness, sleepiness, convulsions, rapid heart rate, and death. Health effects, health impacts or health risks are an important consideration in many areas, such as hygiene, pollution studies, workplace safety, nutrition and health sciences in general. ... Death is either the cessation of life in a living organism or the state of the organism after that event. ... A headache is a condition of mild to severe pain in the head; sometimes upper back or neck pain may also be interpreted as a headache. ... In anatomy, the stomach (in ancient Greek στόμαχος) is an organ in the alimentary canal used to digest food. ...

The major effect of benzene from chronic (long term) exposure is to the blood. Benzene damages the bone marrow and can cause a decrease in red blood cells leading to anemia. It can also cause excessive bleeding and depress the immune system, increasing the chance of infection. Medicine In medicine, a persistent and lasting condition is said to be chronic (from Greek chronos). ... Red blood cells (erythrocytes) are present in the blood and help carry oxygen to the rest of the cells in the body Blood is a circulating tissue composed of fluid plasma and cells (red blood cells, white blood cells, platelets). ... Bone marrow is the tissue comprising the center of large bones. ... Anemia (American English) or anaemia (Commonwealth English), which literally means without blood, is a lack of red blood cells and/or hemoglobin. ... The immune system is the organ system that protects an organism from outside biological influences. ... An infection is the detrimental colonization of a host organism by a foreign species. ...

Some women who breathed high levels of benzene for many months had irregular menstrual periods and a decrease in the size of their ovaries. It is not known whether benzene exposure affects the developing fetus in pregnant women or fertility in men. The menstrual cycle is the periodic change in a womans body that occurs every month between puberty and menopause and that relates to reproduction. ... Human female internal reproductive anatomy Ovaries are a part of a female organism that produces eggs. ... Fetus at eight weeks A fetus (alternatively foetus or fœtus) is an unborn human offspring from the end of the 8th week of pregnancy (when the major structures have formed) until birth. ...

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

The US Department of Health and Human Services (DHHS) classifies benzene as a human carcinogen. Long-term exposure to high levels of benzene in the air can cause leukemia, a fatal cancer of the blood-forming organs. The United States Department of Health and Human Services, often abbreviated HHS, is a Cabinet department of the United States government with the goal of protecting the health of all Americans and providing essential human services. ... In pathology, a carcinogen is any substance or agent that promotes cancer. ... Leukemia (leukaemia in Commonwealth English) is a group of blood diseases characterized by malignancies (cancer) of the blood-forming tissues. ...

Several tests can show if you have been exposed 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, since benzene disappears rapidly from the blood, measurements are accurate only for recent exposures.

In the body, benzene is metabolized. Certain metabolites can be measured in the urine. However, this test must be done shortly after exposure and is not a reliable indicator of how much benzene you have been exposed to, since the same metabolites may be present in urine from other sources. Santorio Santorio (1561-1636) in his steelyard balance, from Ars de statica medecina, first published 1614 Metabolism (from μεταβολισμος(metavallo), the Greek word for change), in the most general sense, is the ingestion and breakdown of complex compounds, coupled with the liberation of energy, and the consequent generation of waste...

The US 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. EPA redirects here. ...

The US 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 United States Occupational Safety and Health Administration (OSHA) was created by Congress under the Occupational Safety and Health Act, signed by President Richard M. Nixon on December 29, 1970. ...

Benzene exposure

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.

See also

• Simple aromatic ring for analogs of benzene

Simple aromatic rings are aromatic organic compounds (also known as arenes or aromatics) that consist only of conjugated planar ring systems with delocalized pi electron clouds instead of discrete alternating single and double bonds. ...

External links

• Loschmidt's Benzene structure (http://www.physicstoday.org/pt/vol-54/iss-3/captions/p45cap4.html)
• Benzene Material Safety Data Sheet (http://www.hazard.com/msds/f2/bqv/bqvjq.html)

References

• Archibald Scott Couper, On a New Chemical Theory, Philosophical Magazine 16, 104-116 (1858)
• Josef Loschmidt, Chemische Studien I, Carl Gerold's Sohn, Vienna (1861),
• Josef Loschmidt, Chemische Studien I, Aldrich Chemical Co, Milwaukee (1989), catalog no. Z-18576-0, and (1913) catalog no. Z-18577-9
• Kathleen Lonsdale, "The Structure of the Benzene Ring in Hexamethylbenzene," Proceedings of the Royal Society 123A: 494 (1929).
• Kathleen Lonsdale, "An X-Ray Analysis of the Structure of Hexachlorobenzene, Using the Fourier Method," Proceedings of the Royal Society 133A: 536 (1931).