Toluene, or methylbenzene, is a clear liquid that is insoluble in water and smells like paint thinner. It is miscible with most organic solvents and is commonly used as an organic solvent itself. Despite the chemical’s known hazards, enough evidence does not exist to list it definitively as a carcinogen.
Toluene consists of a six-membered ring of carbon atoms, with hydrogen atoms attached to five of the carbons and a methyl (CH3) group attached to the sixth. It is classified as an aromatic compound because of its structure. Instead of adjacent carbon atoms being connected by distinct single or double bonds, the ring of carbon atoms is held together by single bonds plus a ring of electrons (a continuous pi bond), which are not localized as in normal carbon-containing molecules.
Source and Production
Toluene is a naturally-occurring component of crude oil. It is produced in petroleum refining and is also produced as a byproduct in production of coke for the steel industry. In a chemistry lab product can be made from the reaction of benzene and methyl chloride in the presence of aluminum chloride or by the reaction of bromobenzene with methyl bromide and sodium in a dry ether solvent, among other reactions.
Toluene is primarily used as an octane-boosting additive to gasoline. It is also used as a solvent in paints, household aerosols, adhesives, solvent-based cleaning agents, and synthetic fragrances. Toluene is also used to make benzene and other organic chemicals and in the production of polymers such as nylon and polyethylene terephthalate (used to make soda bottles). In addition, methylbenzene is used in leather tanning and printing operations.
Toluene(CAS No. 108-88-3) has been abused as an inhalant, and when used this way it can cause permanent changes to the human brain through repeated exposure in high concentrations. In daily living, people can be exposed to its vapors from car exhaust, contaminated air in a workplace or from breathing the vapors while painting machinery or polishing the fingernails with certain nail lacquers. Exposure also can occur when living near a site that has been contaminated, such as a waste or dump site, or when working daily with products that have been made with the chemical, such as heating oil, kerosene and gasoline.
Exposure threatens children as well as adults. Children can experience symptoms similar to those adults face when exposed to the chemical. Pregnant women also are greatly affected because exposure to high levels can lead to physical birth defects and also affect a baby’s mental capabilities.