Benzene is a hydrocarbon with the chemical formula C6H6. Its bonds are arranged in a closed loop, and it is colourless or light yellow chemical that is liquid at room temperature. It has a sweet odour, is highly flammable, and evaporates easily into the air. It dissolves only slightly in water and its vapour is heavier than air. Benzene belongs to a class of chemicals known as the aromatic hydrocarbons. These hydrocarbons are given this name as a result of their characteristic smell. It is important to note that benzene is an example of an aromatic compound and many aromatic compounds have a benzene ring in their structure. While many aromatic compounds include a benzene ring, there are additional requirements that must be met for a chemical to be considered aromatic in addition to the presence of a benzene ring in its structure. For a more in-depth definition of what an aromatic compound is, click here.
Some additional properties of benzene are outlined in the table below.
|Molar mass||77.81 grams/mole|
For more information on the unique properties of benzene, see UC Davis' ChemWiki.
The formation of benzene can occur both naturally and as a result of human activities. Benzene can be released naturally from volcanoes or forest fires. Benzene is also found naturally in crude oil, gasoline, and cigarette smoke.
Benzene is used in a wide number of different applications, and is one of the top 20 most used chemicals in the United States. Frequently, benzene is used as a solvent, and can be used in the manufacturing of detergents, explosives, plastics, lubricants, and pharmaceuticals. Benzene is also a component of motor fuels such as gasoline or diesel.
Benzene is released into the air with other emissions as a result of burning coal or oil. As well, benzene can be found as an emission from gas stations and in motor vehicle exhaust. Indoor air tends to contain more benzene than outdoor air. The benzene in indoor air comes from a combination of products containing benzene including glues, paint, furniture wax, and detergents. However, air around hazardous waste sites or gas stations contain larger levels of benzene than other areas. One of the largest sources of benzene, however, is cigarette smoke.
Exposure to benzene causes a wide range of different health effects. Short-term inhalation of benzene can result in dizziness, tiredness, headaches, along with eye, skin, and throat irritation. At high levels, exposure to benzene can result in unconsciousness.
Exposure to benzene over a long period of time can result in a variety of different disorders, including blood disorders such as anemia. It has also been shown that inhalation of benzene can have harmful effects on developing fetuses. Because benzene is a carcinogen, long-term exposure to it can result in an increased risk of developing cancer. In particular, research has shown long-term exposure to benzene increases the risk of developing leukemia and cancers of other blood cells.