Other Definitions
butadiene (dict)
|
Butadiene Butadiene can refer to either one of two hydrocarbon chemical compounds which are alkenes that are isomers of each other. They are both dienes having the chemical formula C4H6 and are both gases at room temperature and pressure. 1,3-butadiene is a simple conjugated diene having the chemical structure shown at right. It is an important industrial chemical used as a monomer in the production of synthetic rubber. When the word butadiene is used, most of the time it refers to 1,3-butadiene. The name butadiene can also refer to the isomer, 1,2-butadiene, which is a cumulated diene. However, this allene is difficult to prepare and has no industrial significance. The remainder of this article concerns 1,3-butadiene. History Throughout the later 19th century, many chemists attempted to determine the makeup of natural rubber, with the goal of reproducing it. In 1860, the British chemist Charles Greville Williams analyzed rubber by destructive distillation and obtained a large quantity of a light oil which he termed isoprene. In 1873, the French chemist Georges Bouchardat found that isoprene, when heated with hydrochloric acid for several hours, produced a rubber-like substance. In 1882, another British chemist Sir William Augustus Tilden distilled isoprene from turpentine. Tilden found a number of ways to prepare rubber materials from isoprene, but none were commercially practical, and so by the 1890s he abandoned synthetic rubber research. Before doing so, however, Tilden determined the structure of isoprene, opening the door to producing rubbers from chemicals with similar structures, the simplest of which is butadiene. In 1910, the Russian chemist Sergey Lebedev prepared a butadiene polymer with rubber-like properties. This polymer was, however, too soft to replace natural in many roles, especially automobile tires. The butadiene industry originated in the years leading up to World War II. Many of the belligerent nations realized that in the event of war, they could be cut off from rubber plantations controlled by the British Empire, and sought to remove their dependence on natural rubber. In 1929, Eduard Tschunker and Walter Bock, working for I.G. Farben in Germany, made a copolymer of styrene and butadiene that could be used in automobile tires. Worldwide production quickly ensued, with butadiene being produced from grain alcohol in the Soviet Union and the United States and from coal-derived acetylene in Germany. Production In the United States, western Europe, and Japan, butadiene is produced as a byproduct of the steam cracking process used to produce ethylene. Butadiene is isolated from the other hydrocarbons produced in steam cracking by extraction into a solvent such as acetonitrile or dimethylformamide, from which it is then stripped by distillation. In other parts of the world, including eastern Europe, China, and India, butadiene is also produced from ethanol via the intermediate crotonaldehyde. Uses Most butadiene is polymerized to produce synthetic rubber. While polybutadiene itself is a very soft, almost liquid material, polymers prepared from mixtures of butadiene with styrene or acrylonitrile, such as ABS, are both tough and elastic. Styrene-butadiene rubber is the material most commonly used for the production of automobile tires. Smaller amounts of butadiene are used to make nylon via the intermediate adiponitrile, other synthetic rubber materials such as chloroprene, and the solvent sulfolane. Safety Contact with liquid butadiene can result in irritation of the skin, eyes, and mucous membranes. Since it often stored as a refrigerated liquid, frostbite is another possible consequence of exposure. When inhaled, butadiene is a mild depressant and can result in drowsiness, although very high concentrations are necessary to produce unconsciousness or death. In some animals, long-term exposure to butadiene can result in cancer of the liver or kidneys. Butadiene is a potent carcinogen in mice, but only a weak carcinogen in rats. Studies of workers in chemical plants using butadiene have shown no conclusive increase in cancer risk for whatever amount of butadiene these workers may have been exposed to, so butadiene remains classified as only a potential human carcinogen.
|
 |