Benzene

Benzene is an organic compound possessing a ring structure containing six hydrogen atoms and six carbon atoms. It was first isolated and identified by the creation scientist Michael Faraday in 1825. It is a commonly used to make other chemical derivative which are in turn used in various products today. For example, styrene is used to make polymers and plastics, and phenol is used to make many resins and adhesives.

History
At one time, benzene was a challenging puzzle to chemists. More than forty years after Faraday's initial discovery of benzene, chemists still had not been able to discover its chemical structure. In 1865, German chemist Friedrich August Kekulé finally solved the puzzle. He claimed that his dream about a snake with a tail in its mouth made him realize that the structure of benzene was a ring with a hydrogen atom attached to each carbon atom.

After the discovery of benzene's unique structure, chemists have been able to utilize the compound to produce useful derivatives, such as synthetic rubber. Although the compound can be toxic, benzene is still an extremely useful compound.

Properties
Benzene, a colorless or light yellow liquid, has the chemical formula, C6H6. This aromatic hydrocarbon has a unique, polyunsaturated structure that is arranged in a hexagonal-type ring. The carbon atoms are connected to two other carbon atoms via the alternation of double carbon bonds. Each carbon atom has a single or double bond with two other carbon atoms and a single bond to one hydrogen atom. Each of those carbon-carbon bonds have been discovered to measure 140 picometres, which is shorter than a double bond but larger than a single bond. This distance is caused by electron delocalization, in which the electrons are spread equally apart from the 6 carbon atoms. This aromatic structure makes it a relatively stable compound. In chemical reactions, benzene tends to undergo substitution reactions, reactions in which an atom or group of atoms replaces another atom or group of atoms. Two or three substitutions can occur on one benzene ring. The halogens, nitric acid, sulfuric acid, and alkyl halides react with benzene, forming substituted derivatives. It has a melting point at 5.5°C, a boiling point 80.1°C, and is highly flammable. It has a sweet smell, similar to that of petrol. Benzene is also volatile and dissolves readily in water.

Occurrences
Benzene is both a natural and man-made compound. In nature, it is often found as a product of carbon-rich materials that undergo incomplete combustion.Benzene can be found from volcanoes, forest fires, and petroleum.Some plants and animals also contain this compound. It can also be found in crude oil, gasoline, and cigarette smoke. Humans are generally exposed through it through low levels in outdoor air from tobacco smoke, gas stations, motor vehicle exhaust, and even industrial emissions. In fact, hazardous waste sites and gas stations have the highest concentrations of benzene in the air. Indoor air generally has a higher concentration of benzene, because of indoor products such as glues, paints, furniture wax, and detergents. Benzene evaporates very quickly into the air, but its vapor sinks lower than the air. When benzene is released to soil, it can break down quickly and will react with other chemicals to produce photochemical smog, which is unhealthy for the environment.

Uses
Before it was discovered to be toxic, benzene was used as an aftershave lotion for its sweet smell and even used to decaffeinate coffee. Students in university laboratories were even commonly exposed to it in the laboratories. However, after benzene was discovered to be toxic, the general usage became more common for commercial and industrial practices.  It is a versatile compound and is in high demand for many industries, being in the top 20 in production volume for chemicals produced in the United States. It serves as a solvent in many different operations, including industrial, research, and commercial. Because of its high octane number, it is used as a gasoline additive for European manufacturers to improve the starting qualities and engine efficiency.The most important use of benzene is to produce other aromatic compounds, which are compounds that contain at least one benzene ring. Scientists have derived commercially valuable polymers, such as polystyrene, nylon, and synthetic rubber from benzene. Over half of benzene in chemical synthesis is used to produce ethylbenzene, which is treated to produce polystyrene, (C6H5C2H5).Benzene is found in everything from rubber, lubricants, detergents, pesticides, inks, paints, and dyes to pharmaceuticals and explosives.

Toxicity
Although it's a useful compound, benzene is harmful to humans and has been described by the U.S. Department of Health and Human Services as a human carcinogen (cancer causing agent). Exposure to it, whether through oral consumption, inhalation, or contact with the skin, can result in several acute or chronic effects.]Benzene is rapidly absorbed through the lungs, with studies showing that one half of the inhaled benzene is absorbed by the lungs. The absorbed benzene readily distributes into different tissues in the body, including the fatty tissue. It targets the liver, kidney, lung, heart, brain, and bone marrow. It has even been shown to damage DNA. Inhalation of benzene may result in irritation of the mucous membranes, headache, instability, euphoria, convulsions, excitement or depression, and even unconsciousness. Consumption of benzene may cause pneumonia or bronchitis. When benzene has contact with the skin, it may cause drying, blistering, and redness. High concentrations can be lethal, possibly causing lowered blood cell counts and even leukemia.

Humans are not the only ones affected by benzene. Benzene produces an acute toxic effect on aquatic life, causing shorten lifespans, reproductive problems, and changes in appearance and behavior. Benzene is even toxic to plants, which die or get damaged leaves. With industrial use, cigarette smoke, and fuel emissions, benzene has become more common in the environment, endangering lives of both animals and humans.