- Also spelled:
- tetraethyllead
- Key People:
- Thomas Midgley, Jr.
- Related Topics:
- organometallic compound
- lead poisoning
tetraethyl lead
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What is tetraethyl lead?
Tetraethyl lead (TEL) is an organometallic compound with the chemical formula (C_8H_{20}Pb). It was once a common antiknock agent for automotive gasoline but has been phased out due to environmental concerns and health risks.
TEL is manufactured through the reaction of ethyl chloride with a powdered alloy of lead and sodium. It is a dense, colorless, and volatile liquid. When added to gasoline, TEL prevents engine knock by forming lead oxide during combustion. However, the use of TEL in gasoline has been linked to lead poisoning and interference with pollution-control devices. Because of these health concerns, leaded gasoline was phased out, starting in the 1970s in the United States and later in Europe and worldwide.
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What is tetraethyl lead used for?
Tetraethyl lead (TEL) was primarily used as an antiknock agent for automotive gasoline (petrol). Adding TEL to gasoline in small amounts improved engine performance by preventing engine knock. However, due to concerns about lead poisoning and its interference with pollution-control devices, its use was phased out starting in the 1970s in the United States, Europe, and worldwide. Although banned in many countries, TEL continued to be used in aviation gasoline and racing fuel for many years.
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How does tetraethyl lead help gasoline engines?
Tetraethyl lead (TEL) was used as an antiknock agent for gasoline. In hot gasoline engines, the bonds between the lead atom and the ethyl groups are broken. Upon combustion, the lead atom forms lead oxide (PbO), preventing the fuel mixture from burning too quickly and causing engine knock.
TEL was added to gasoline in small quantities to improve engine performance. Ethylene bromide was also added to the gasoline to prevent lead deposits in the cylinders. The lead and bromine formed a compound that left the engine in the exhaust. However, due to its contribution to lead poisoning and interference with pollution-control devices, the use of leaded gasoline has been phased out.
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Why was tetraethyl lead added to gasoline in the past?
Tetraethyl lead (TEL) was added to gasoline as an antiknock agent to improve engine performance. Adding TEL in small quantities to gasoline considerably improved engine performance starting in the 1920s. It prevented the fuel mixture from burning too quickly, which caused engine knocking. The practice of adding tetraethyl lead to gasoline has ended because it was found to contaminate exhaust gases with poisonous lead oxides.
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What are the health and environmental risks of using tetraethyl lead?
Tetraethyl lead (TEL) is a toxic organometallic compound that was once the primary antiknock agent for automotive gasoline. The health risks of TEL include acute or chronic lead poisoning through inhalation or skin absorption. Symptoms of lead poisoning include abdominal pain, diarrhea, nausea, and neurological issues, especially in children, such as learning disabilities and slowed development.
The environmental risks of TEL stem from its use as a gasoline additive, which led to widespread lead pollution. The Environmental Protection Agency (EPA) phased out leaded gasoline due to its interference with pollution-control devices in vehicles. The elimination of TEL in gasoline has greatly reduced lead poisoning.
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Why was tetraethyl lead phased out of gasoline worldwide?
Tetraethyl lead (TEL) was phased out of gasoline worldwide because of its contribution to lead poisoning and its interference with pollution-control devices in cars. Studies in the 1960s and 1970s showed the accumulation of lead in industrial nations and the effects of lead poisoning on children's intellectual development. In 1972, the U.S. Environmental Protection Agency announced that leaded gasoline would be phased out because lead interfered with new smog-reducing catalytic converters. TEL use has declined since the mid-1970s due to environmental restrictions. The toxicity of lead compounds increases as their solubility increases.
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tetraethyl lead (TEL), organometallic compound containing the toxic metal lead that for much of the 20th century was the chief antiknock agent for automotive gasoline, or petrol. Beginning in the 1970s, āleaded gasolineā was phased out, first in the United States and then in Europe and around the world, on account of its contribution to lead poisoning and its interference with pollution-control devices installed in automobiles.
The compound, manufactured by the action of ethyl chloride on a powdered alloy of lead and sodium, is a dense, colourless liquid that is quite volatile, boiling at about 200 Ā°C (400 Ā°F). The molecule consists of a single atom of lead (Pb) bonded to four ethyl groups (CH2CH3) through a carbon (C) atom. The resulting arrangement has the chemical formula C8H20Pb and adopts a tetrahedral structure, as shown in the .
In the hot cylinder of a gasoline engine, the bonds between the lead atom and the ethyl groups are broken. Upon combustion, the lead atom forms lead oxide (PbO), which prevents fractions of the fuel mixture from burning too quickly and causing a highly undesirable āengine knock.ā Beginning in the 1920s, TEL, added to gasoline in very small quantities (not exceeding 3 cubic cm per gallon), considerably improved engine performance. To prevent accumulation of lead deposits in the cylinders, a small quantity of ethylene bromide was added to the gasoline. The lead and bromine formed a compound that left the engine in the exhaust.
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TEL can cause acute or chronic lead poisoning if inhaled or absorbed through the skin. Indeed, the industrial chemist widely given credit for discovering the antiknock properties of the compound, Thomas Midgley, Jr., was forced to leave his job for several months in 1923 in order to recuperate from lead poisoning. From 1923 to 1925 several workers suffered agonizing deaths from acute lead poisoning at the first plants built by the General Motors Corporation, the DuPont Company, and the Standard Oil Company (New Jersey) for producing TEL on an industrial scale. The dangers of lead poisoning were well known at the time, publicized by such occupational-health advocates as Alice Hamilton of Harvard Medical School. Procedures were installed at TEL plants for safely processing the compound, and officials from the automobile and oil industries (including Midgley himself) succeeded in convincing government health authorities and regulators that the minute quantities of lead emitted from engine exhaust had not been proved to constitute a danger to public health. As a result, use of TEL was approved, and āethyl gasolineā became the standard antiknock formulation for use in automobile engines.
Studies of the prevalence of lead poisoning continued, however, and resulted in reports by geochemist Clair Patterson in the 1960s on the accumulation of lead in industrial nations and by pediatrician Herbert Needleman in the 1970s on lead poisoning and intellectual development in children. Finally, in 1972 the U.S. Environmental Protection Agency announced that leaded gasoline would be phased outānot specifically to combat lead poisoning but because lead was known to interfere with new smog-reducing catalytic converters that from 1975 would be built into new cars. Use of TEL declined markedly from 1975 to 1985, and since 1995 no leaded gasoline has been available for use in passenger automobiles in the United States. (The use of TEL continued for many years in aviation gasoline and racing fuel, however.) The use of leaded gasoline in cars was banned in Canada in 1990 and in the European Union in 2002. In 2011 the United Nations Environment Programmeās Partnership for Clean Fuels and Vehicles was able to announce that the sale of leaded gasoline had disappeared in all but a small handful of countries and that the use of TEL in even those countries would soon end.