The pure material, and any solutions containing it, constitute a fire risk. Aromatic compounds early in the history of organic. This file is licensed under the creative commons attributionshare alike 3. Pdf many countries in the world have had regulations on benzene with varying enforcement stringency for many decades. The benzene content of printing materials was noted in several studies. Benzene is a hazardous air pollutant that may cause cancer as well as damage to reproductive, immune, and neurologic systems in exposed populations. According to molecular orbital theory for benzene structure, benzene ring involves the formation of three delocalized. Benzene is a clear, colorless, flammable liquid with a. Safety and health topics benzene occupational safety. P r e fa c e osha has a remarkable 37year history of protecting the safety and health of the nations working men and women. Benzene occurs naturally in crude oil and is widely used in industry as a raw material for the production of other organic chemicals. This volume presents an evaluation of the carcinogenicity of benzene, updating with new data the most recent evaluation provided in volume 100f of the iarc monographs.
Aromatic compounds show chemical properties that are only characteristic of aromatic compounds instead. Manipulated data in shells benzene historical exposure study. Benzene is a colorless and highly flammable liquid with a sweet smell and a relatively slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. All structured data from the file and property namespaces is available under the creative commons cc0 license. It could be famous because of its structure which is cyclic or due to its stability compared to others hydrocarbons benzene is more stable than other hydrocarbons.
Though benzene contains three double bonds, its chemical behavior is completely different from that of alkenes. Benzene has a relatively high vapor pressure and thus evaporates quickly into the air. If benzene must be used in an experiment, it should be handled at all stages in a fume cupboard. A history of the structural theory of benzene the aromatic sextet. Benzene is a carcinogen a chemical that causes cancer. Benzene molecules are a ring of six carbon atoms that are each bonded to one hydrogen atom. Washington health system occupational medicine 95 leonard avenue, bldg. First described in the 16th century, benzoic acid exists in many plants. It was also quickly discovered that these aromatic. Bond lengths of benzene bond lengths nm cc cyclohexane 0. As it is categorized as organic compaund, benzene can be treated by common organic reaction, e.
This contamination is a public health concern and has caused significant outcry among environmental and health advocates. Benzene, a simple aromatic hydrocarbon, occurs naturally and as a result of human activity, notably as a result of. Benzene is an important organic chemical compound with the chemical formula c6h6. In addition, another common naming tool for benzene derivates. Benzene c6h6 definition, discovery, structure, resonance. Pdf benzene is a hexagonal molecule of six carbon atoms, each of which is bound to six. Exposure recommendations by 1939, the vast number of benzene poisonings among workers in all parts of the world led to the recommendation for the substitution of.
Its vapor is heavier than air and may sink into lowlying areas. It is an aromatic compound, meaning the ring has alternating double bonds benzene is carcinogenic, which means it can cause cancer. Benzene is found in crude oils and as a byproduct of oilrefining processes. Benzene physical and chemical properties chemistry byjus. Friedelcrafts alkylation was first discovered by french scientist charles friedel and his partner, american scientist james crafts, in 1877. It is a colorless and flammable liquid with a sweet smell. Have you ever been off work for more than 1 day because of an illness related to work. The word benzene derives from gum benzoin benzoin resin, an aromatic resin known to european pharmacists and perfumers since the 16th century as a product of southeast asia. Benzene in soft drinks is of potential concern due to the carcinogenic nature of the benzene molecule.
The resonance hybrid, which is a blend of the contributors, best represents reality. Benzene is a component of products derived from coal and petroleum and is found in gasoline and other fuels. Benzene is an organic chemical compound with the molecular formula c6h6. Concerns about negative health effects related to air quality led to the limitation of benzene content in gasoline to about 1 percent. It a good visualization of the boiling of electronpositron pairs, which always occurs in chemical bonding with any multiplicity. The source of the nitronium ion is through the protonation of nitric acid by. An acidic material was derived from benzoin by sublimation, and named flowers of benzoin, or benzoic acid. The astm d835 refined benzene 485 grade specification is the least stringent, d2359 is higher quality and the d4734 refined benzene 545 is an even higher quality. Benzene is a widely used solvent and is present in gasoline, automobile emissions, and cigarette smoke. Benzene dissolves only slightly in water and will float on top of water.
The benzene molecule is composed of 6 carbon atoms. Cdc niosh pocket guide to chemical hazards benzene. Benzene has several applications in the manufacturing industry. In industry benzene is used as a solvent, as a chemical intermediate, and is used in the synthesis of numerous chemicals. Us epa regulations had further lowered the benzene content to 0. Benzene is a colorless liquid with a characteristic odor and is primarily used in the production of polystyrene. Analysis of historical exposures of pressmen to airborne. Benzene is a clear, colorless, highly flammable and volatile, liquid aromatic hydrocarbon with a gasolinelike odor. This indicator presents trends in ambient concentrations of benzene for 22 locations across the u. However, the structure benzene attracted lot of attention when it was first discovered in the 19th century. However, benzene is in principal organic contaminant class iv as defined in 700. Have you ever been advised to change jobs or work assignments because of. The iupac name of 1,3,5cyclohexatriene is never used.
Benzene is an important commercial commodity and has become widespread in the environments of developed countries. With exposures from less than five years to more than 30 years, individuals have developed, and died from, leukemia. This page was last edited on 10 august 2018, at 16. The benzene content decreased sharply in the 1970s, but today trace benzene concentrations are still present in many petroleumbased solvents. Following maltoni and his colleagues seminal finding of the carcinogenicity of benzene to laboratory animals in 1979, 40 they and others more definitively elucidated the carcinogenesis of benzene in a series of papers 4147 using their unique bioassay exposure design with various experimental protocols. The odor threshold for benzene has been reported as 12 parts per million. The modern theory of benzene structure is not simply one more of the. The various astm specifications for benzene are based mainly on enduse requirements. Department of labor occupational safety and health administration january 2009 osha 3360. Acute shortterm inhalation exposure of humans to benzene may cause drowsiness, dizziness, headaches, as well as eye, skin, and respiratory tract irritation, and, at high levels. Nitration and sulfonation of benzene chemistry libretexts. Benzene is considered as one of the fundamental structures in organic chemistry. Aromatic compounds early in the history of organic chemistry late. Osha had originally used its carcinogen policy to regulate benzene.
The resonance contributors of benzene are pure fantasy. Revision history may 2008 original indicator posted. Benzene is a parent hydrocarbon of all aromatic compounds. In the united states, gasoline contains up to 2% benzene by volume. Occupational exposure inventory please select the appropriate answer. The common name of benzene dominates naming of these structures. The agency has helped to save many thousands of lives and reduce occupational injury and.
Benzene c6h6 benzene is an organic compound with the chemical formula c6h6. Benzene, also known as benzol, is an organic chemical compound with the formula c 6 h 6. Michael faraday was the scientist who first discovered benzene ring in the year 1825. We got a beautiful quantummechanical pattern of a benzene molecule with a threeelectron bond. Background informationbenzene is a clear, colorless liquid at ambient temperatures. Benzene does not have a specific mcl as defined in 700. Benzene is used in the manufacture of plastics, detergents, pesticides, and other chemicals.
Abel, john digiovanni, in the molecular basis of cancer third edition, 2008. Benzene 71432 hazard summary benzene is found in the air from emissions from burning coal and oil, gasoline service stations, and motor vehicle exhaust. Benzene c6h6 is known as the most famous aromatic cyclic hydrocarbons. This reaction allowed for the formation of alkyl benzenes from alkyl halides, but was plagued with unwanted supplemental activity that reduced its effectively. Benzene simple english wikipedia, the free encyclopedia. In the 1930s, 1940s, and 1950s, solvents, inks, and cleaning agents contained a high percentage of benzene. Benzene levels are regulated in drinking water nationally and internationally, and in bottled water in the united states, but only informally in soft drinks. Files are available under licenses specified on their description page.
The sordid history behind the current news on benzene. It is a compound consisting of only hydrogen and carbon atoms. It has the formula c6h6 and can be shown in many different ways, some of which are shown in figure 1. History of occurrence benzene replaced lead as a gasoline additive for its antiknock properties. Benzene is an organic compound found most often in air as a result of emissions from burning coal and oil, gasoline vapors at gasoline service stations, motor vehicle exhaust, cigarette smoke, woodburning fires, some adhesives, and other sources 1, 2. Historically, highlevel exposure to benzene was commonplace, and, in general, benzene exposure has been the cause of great concern due to its carcinogenic properties. Because benzene has the simplest and most funda mental structure of the aromatic compounds, it has been the starting point for studying. Environmental protection agency has established a maximum contaminant level goal mclg of zero ugl and. The benzene standard then went to the supreme court which issued the famous benzene decision from that point on, osha was required to conduct quantitative risk assessments for all health standards. The fact that benzene had a formula c 6 h 6 that suggested a polyene structure i. Benzene is a cyclic hydrocarbon with a chemical formula c 6 h 6, that is, each carbon atom in benzene is arranged in a sixmembered ring and is bonded to only one hydrogen atom. The hydrocarbon derived from benzoic acid thus acquired the name benzin, benzol, or benzene. Benzene should not be used at all unless no safer alternatives are available. Nitration and sulfonation of benzene are two examples of electrophilic aromatic substitution.
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