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{{Chembox new| Name = Tetra-ethyl lead| ImageFile = Tera-ethyl-lead-chemical.png| IUPACName = Tetraethyllead| OtherNames = TEL; lead tetraethyl; tetra-ethyl lead| Section1 = {{Chembox Identifiers| SMILES = CC(CC)(CC)CC| CASNo = 78-00-2| RTECS = TP4550000 --> | Section2 = {{Chembox Properties| Formula = C8H20Pb| MolarMass = 323.44 g/mol| Appearance = colorless, viscous liquid| Density = 1.653 g/mL at 25 °C| Solubility = insoluble| MeltingPt = −136 °C| BoilingPt = 84–85 °C@15 mm Hg| Viscosity =| RefractIndex = 1.519 --> | Section3 = {{Chembox Structure| MolShape = tetrahedral| Dipole = 0 Debye --> | Section7 = {{Chembox Hazards| MainHazards = toxic, flammable| NFPA-H = 3| NFPA-F = 2| NFPA-R = 3| FlashPt = 346 K - 73 °C - 163 °F| RPhrases = , , , , | SPhrases = , , , --> | Section8 = {{Chembox Related| OtherAnions = Tetraphenyllead| OtherCations = Tetramethylsilane; [tetramethyltin; decaphenylplumbocene --> -->Tetra-ethyl lead, abbreviated TEL, is an organometallic chemistry compound with the formula (ethyl)4lead. Once a common Engine knocking additive in gasoline (petrol), TEL usage was largely discontinued because of the toxicity of lead and its Catalytic converter#Catalyst poisoning and deactivation on catalytic converters. It is still used as an additive in the aviation fuel known as avgas.

Synthesis and properties TEL is produced by reacting ethyl chloride with a sodium-lead alloy.Seyferth, D., "The Rise and Fall of Tetraethyllead. 2", Organometallics, 2003, volume 22, pages 5154-5178. :4 NaPb + 4 CH3CH2Cl → (CH3CH2)4Pb + 4 NaCl + 3 Pb The product, TEL, is a Viscosity colorless liquid. Because TEL is charge neutral and contains an exterior of alkyl groups, it is highly Lipophilicity and soluble in petrol (gasoline).

A noteworthy feature of TEL is the weakness of its four C-Pb bonds. At the temperatures found in internal combustion engines (CH3CH2)4Pb decomposes, first into (CH3CH2)3Pb and ethyl Radical (chemistry)s. These radicals scavenge other radicals, thereby preventing the initiation of combustion, which itself is a radical reaction, in order to delay ignition. When (CH3CH2)4Pb burns, it produces not only carbon dioxide and water, but also lead: : (CH3CH2)4Pb + 13 O2 → 8 CO2 + 10 H2O + Pb This lead can oxidize further to give species such as lead oxide: :2Pb + O2 → 2PbO The Pb and PbO would quickly accumulate and destroy an engine. For this reason, lead scavengers such as 1,2-Dibromoethane and 1,2-Dichloroethane are used in conjunction with TEL - these agents form volatile lead(II) bromide and lead(II) chloride, respectively, which are exhausted from the engine (and into the air).

Formulation of ethyl fluid Tetra-ethyl lead was supplied for mixing with raw gasoline in the form of "ethyl fluid", which was tetra-ethyl lead blended together with the lead scavengers 1,2-Dibromoethane and 1,2-Dichloroethane. Ethyl fluid also contained a reddish dye which would distinguish treated gasoline from untreated gasoline and discourage the diversion of gasoline for other purposes such as cleaning.

Ethyl fluid was added to gasoline at rate of 1:1260, usually at the refinery. Because of the widespread use, specialised and toxic nature of ethyl fluid, the Ethyl Corporation developed an expertise in the handling and formulation of toxic organometallics. Despite this, some 17 workers for the Ethyl Corporation and Standard Oil died during the 1920s from the effects of exposure to lead.

The classical formula for ethyl fluid is:



Uses of TEL as an antiknock agent TEL was once used extensively as an gasoline additive in gasoline (petrol) for its ability to increase the fuel's octane rating (that is, to prevent its premature detonation ("Engine knocking") in the engine) thus allowing the use of higher compression ratios for greater fuel efficiency and power (physics).The use of TEL in gasoline was started in the US while in Europe alcohol was initially used. The advantages of ethyl gasoline from its higher energy content and storage quality eventually led to a universal switch to leaded fuel. One of the greatest advantages of TEL over other anti-knock agents or the use of high octane blend stocks is the very low concentrations needed. Typical formulations called for 1 part of ethyl fluid (prepared TEL) to 1260 parts untreated gasoline. Competing anti-knock agents must be used in higher amounts and/or have a much lower energy level than natural gasoline. The higher energy content of ethyl gasoline results in greater fuel efficiency.

When used as an antiknock agent, alcohol will cause fuel to absorb moisture from the air. Over time high fuel humidity can rise leading to rusting and corrosion in the fuel line. Whereas TEL is highly soluble in gasoline, ethanol is poorly soluble and that solubility decreases as fuel humidity increases. Over time droplets and pools of water can form in the fuel system creating a risk for fuel line icing. High fuel humidity can also raise issues of biological contamination, as certain bacteria can grow in on surface of the water/gasoline interface thus forming bacterial mats in the fuel system. TEL's biocidal properties help prevent fuel contamination and degradation from bacterial growth.

In most Western nation this additive went out of use in the late 20th century, because of the concerns over air pollution. Use of TEL as a fuel additive would result in the fouling of catalytic converters. The need for TEL was lessened by several advances in automotive engineering and petroleum chemistry. Lower oil prices promoted the development of low compression engines that were not as sensitive to gasoline quality.Other anti-knocking additives (Methylcyclopentadienyl Manganese Tricarbonyl) and cheaper methods for making higher octane blending stocks (reformate) reduced the need for TEL.

As of 2007, unleaded automotive gasoline is available throughout the world, and the only countries in which leaded gasoline is extensively used are Yemen, Afghanistan and North Korea. Leaded gasoline is still available in parts of Northwest Africa, Europe, Commonwealth of Independent States (CIS), Iraq, Jordan and the Palestinian territories.

TEL remains an ingredient of avgas and high-octane racing fuels. TEL is still in use today as a component of 100 octane rating aviation fuel, as a suitable replacement for it in the aviation industry has not yet been found. The current formulation of 100LL (low lead) aviation gasoline contains much less lead than did historical aviation gasolines.

In earlier times many vehicles produced before TEL's phase-out required modification to a greater or lesser extent to run successfully on unleaded gasoline. The installation of new hardened valve seats can be done by a competent automotive machine shop. A major engine rebuild, generally by the use of dished pistons, is required to reduce the compression ratio of some older high-performance engines (which required 100-octane leaded fuel) to a ratio that is compatible with currently available gasoline ratings and this reform necessarily entails a decrease in engine power. However by the 21st century additives were available to allow continued use of even these sensitive engines, more or less to their normal function.

History TEL was found to be an effective anti-knocking agent by Thomas Midgley in 1921, working under Charles Kettering at General Motors Corporation Research."Leaded Gasoline, Safe Refrigeration, and Thomas Midgley, Jr." Chapter 6 in S. Bertsch McGrayne "Prometheans in the Lab" McGraw-Hill: New York, 2002. ISBN 0-07-140795-2 Due to its extreme toxicity, many early researchers of TEL became Lead poisoning (including Midgley himself), and dozens died . In 1924, Standard Oil of New Jersey (ESSO/EXXON) and General Motors created the Ethyl Corporation to produce and market TEL. In the United States in 1972, the United States Environmental Protection Agency launched an initiative to phase out leaded gasoline, which caused Ethyl Corp. to sue the EPA. The EPA won, so in 1976 the phase out began and was completed by 1986. A 1994 study indicated that the concentration of lead in blood dropped 78% from 1978 to 1991 .

Leaded gasoline phased out European Union-wide on the 1st January 2000, although it had been banned much earlier in some member states. It was only recently phased out in China (around 2001). In the United Kingdom a small amount of leaded gasoline ("four star petrol") is still permitted to be manufactured and sold , albeit with a higher rate of fuel duty.

Even though leaded gasoline is largely gone in North America, it has left high concentrations of lead in the dirt adjacent to all roads that were constructed prior to its phaseout. Child development specialists often advise parents to not let their children play in such dirt, especially because some children like to eat dirt (see Pica (disorder)).

Alternative antiknock agents Since the main problem with TEL is its lead content, many alternative additives that contain less poisonous metals have been examined. Methylcyclopentadienyl Manganese Tricarbonyl (MMT or methylcymantrene) is used as an antiknock agent in Canada, but its use as a fuel additive had been banned in the US until 1995. Ferrocene has also been reported as an effective antiknock agent. It had also been established by 1921 that ethanol was an effective antiknock agent, but TEL was introduced for mainly commercial reasons to replace it.

Improvements of the gasoline itself decrease the need for separate antiknock agents. Synthetic iso-octane and alkylate are examples of such blending stocks.

References "Countries where Leaded Petrol is Possibly Still Sold for Road Use of 17 countries in region, alphabetical and population order" By Elizabeth O'Brien collating data from The LEAD Group, Partnership for Cleaner Fuels & Vehicles (PCFV) & International Fuel Quality Center - http://www.lead.org.au/fs/fst27.html

See also

External links

{{Chembox new| Name = Tetra-ethyl lead| ImageFile = Tera-ethyl-lead-chemical.png| IUPACName = Tetraethyllead| OtherNames = TEL; lead tetraethyl; tetra-ethyl lead| Section1 = {{Chembox Identifiers| SMILES = CC(CC)(CC)CC| CASNo = 78-00-2| RTECS = TP4550000 --> | Section2 = {{Chembox Properties| Formula = C8H20Pb| MolarMass = 323.44 g/mol| Appearance = colorless, viscous liquid| Density = 1.653 g/mL at 25 °C| Solubility = insoluble| MeltingPt = −136 °C| BoilingPt = 84–85 °C@15 mm Hg| Viscosity =| RefractIndex = 1.519 --> | Section3 = {{Chembox Structure| MolShape = tetrahedral| Dipole = 0 Debye --> | Section7 = {{Chembox Hazards| MainHazards = toxic, flammable| NFPA-H = 3| NFPA-F = 2| NFPA-R = 3| FlashPt = 346 K - 73 °C - 163 °F| RPhrases = , , , , | SPhrases = , , , --> | Section8 = {{Chembox Related| OtherAnions = Tetraphenyllead| OtherCations = Tetramethylsilane; [tetramethyltin; decaphenylplumbocene --> -->Tetra-ethyl lead, abbreviated TEL, is an organometallic chemistry compound with the formula (ethyl)4lead. Once a common Engine knocking additive in gasoline (petrol), TEL usage was largely discontinued because of the toxicity of lead and its Catalytic converter#Catalyst poisoning and deactivation on catalytic converters. It is still used as an additive in the aviation fuel known as avgas.

Synthesis and properties TEL is produced by reacting ethyl chloride with a sodium-lead alloy.Seyferth, D., "The Rise and Fall of Tetraethyllead. 2", Organometallics, 2003, volume 22, pages 5154-5178. :4 NaPb + 4 CH3CH2Cl → (CH3CH2)4Pb + 4 NaCl + 3 Pb The product, TEL, is a Viscosity colorless liquid. Because TEL is charge neutral and contains an exterior of alkyl groups, it is highly Lipophilicity and soluble in petrol (gasoline).

A noteworthy feature of TEL is the weakness of its four C-Pb bonds. At the temperatures found in internal combustion engines (CH3CH2)4Pb decomposes, first into (CH3CH2)3Pb and ethyl Radical (chemistry)s. These radicals scavenge other radicals, thereby preventing the initiation of combustion, which itself is a radical reaction, in order to delay ignition. When (CH3CH2)4Pb burns, it produces not only carbon dioxide and water, but also lead: : (CH3CH2)4Pb + 13 O2 → 8 CO2 + 10 H2O + Pb This lead can oxidize further to give species such as lead oxide: :2Pb + O2 → 2PbO The Pb and PbO would quickly accumulate and destroy an engine. For this reason, lead scavengers such as 1,2-Dibromoethane and 1,2-Dichloroethane are used in conjunction with TEL - these agents form volatile lead(II) bromide and lead(II) chloride, respectively, which are exhausted from the engine (and into the air).

Formulation of ethyl fluid Tetra-ethyl lead was supplied for mixing with raw gasoline in the form of "ethyl fluid", which was tetra-ethyl lead blended together with the lead scavengers 1,2-Dibromoethane and 1,2-Dichloroethane. Ethyl fluid also contained a reddish dye which would distinguish treated gasoline from untreated gasoline and discourage the diversion of gasoline for other purposes such as cleaning.

Ethyl fluid was added to gasoline at rate of 1:1260, usually at the refinery. Because of the widespread use, specialised and toxic nature of ethyl fluid, the Ethyl Corporation developed an expertise in the handling and formulation of toxic organometallics. Despite this, some 17 workers for the Ethyl Corporation and Standard Oil died during the 1920s from the effects of exposure to lead.

The classical formula for ethyl fluid is:



Uses of TEL as an antiknock agent TEL was once used extensively as an gasoline additive in gasoline (petrol) for its ability to increase the fuel's octane rating (that is, to prevent its premature detonation ("Engine knocking") in the engine) thus allowing the use of higher compression ratios for greater fuel efficiency and power (physics).The use of TEL in gasoline was started in the US while in Europe alcohol was initially used. The advantages of ethyl gasoline from its higher energy content and storage quality eventually led to a universal switch to leaded fuel. One of the greatest advantages of TEL over other anti-knock agents or the use of high octane blend stocks is the very low concentrations needed. Typical formulations called for 1 part of ethyl fluid (prepared TEL) to 1260 parts untreated gasoline. Competing anti-knock agents must be used in higher amounts and/or have a much lower energy level than natural gasoline. The higher energy content of ethyl gasoline results in greater fuel efficiency.

When used as an antiknock agent, alcohol will cause fuel to absorb moisture from the air. Over time high fuel humidity can rise leading to rusting and corrosion in the fuel line. Whereas TEL is highly soluble in gasoline, ethanol is poorly soluble and that solubility decreases as fuel humidity increases. Over time droplets and pools of water can form in the fuel system creating a risk for fuel line icing. High fuel humidity can also raise issues of biological contamination, as certain bacteria can grow in on surface of the water/gasoline interface thus forming bacterial mats in the fuel system. TEL's biocidal properties help prevent fuel contamination and degradation from bacterial growth.

In most Western nation this additive went out of use in the late 20th century, because of the concerns over air pollution. Use of TEL as a fuel additive would result in the fouling of catalytic converters. The need for TEL was lessened by several advances in automotive engineering and petroleum chemistry. Lower oil prices promoted the development of low compression engines that were not as sensitive to gasoline quality.Other anti-knocking additives (Methylcyclopentadienyl Manganese Tricarbonyl) and cheaper methods for making higher octane blending stocks (reformate) reduced the need for TEL.

As of 2007, unleaded automotive gasoline is available throughout the world, and the only countries in which leaded gasoline is extensively used are Yemen, Afghanistan and North Korea. Leaded gasoline is still available in parts of Northwest Africa, Europe, Commonwealth of Independent States (CIS), Iraq, Jordan and the Palestinian territories.

TEL remains an ingredient of avgas and high-octane racing fuels. TEL is still in use today as a component of 100 octane rating aviation fuel, as a suitable replacement for it in the aviation industry has not yet been found. The current formulation of 100LL (low lead) aviation gasoline contains much less lead than did historical aviation gasolines.

In earlier times many vehicles produced before TEL's phase-out required modification to a greater or lesser extent to run successfully on unleaded gasoline. The installation of new hardened valve seats can be done by a competent automotive machine shop. A major engine rebuild, generally by the use of dished pistons, is required to reduce the compression ratio of some older high-performance engines (which required 100-octane leaded fuel) to a ratio that is compatible with currently available gasoline ratings and this reform necessarily entails a decrease in engine power. However by the 21st century additives were available to allow continued use of even these sensitive engines, more or less to their normal function.

History TEL was found to be an effective anti-knocking agent by Thomas Midgley in 1921, working under Charles Kettering at General Motors Corporation Research."Leaded Gasoline, Safe Refrigeration, and Thomas Midgley, Jr." Chapter 6 in S. Bertsch McGrayne "Prometheans in the Lab" McGraw-Hill: New York, 2002. ISBN 0-07-140795-2 Due to its extreme toxicity, many early researchers of TEL became Lead poisoning (including Midgley himself), and dozens died . In 1924, Standard Oil of New Jersey (ESSO/EXXON) and General Motors created the Ethyl Corporation to produce and market TEL. In the United States in 1972, the United States Environmental Protection Agency launched an initiative to phase out leaded gasoline, which caused Ethyl Corp. to sue the EPA. The EPA won, so in 1976 the phase out began and was completed by 1986. A 1994 study indicated that the concentration of lead in blood dropped 78% from 1978 to 1991 .

Leaded gasoline phased out European Union-wide on the 1st January 2000, although it had been banned much earlier in some member states. It was only recently phased out in China (around 2001). In the United Kingdom a small amount of leaded gasoline ("four star petrol") is still permitted to be manufactured and sold , albeit with a higher rate of fuel duty.

Even though leaded gasoline is largely gone in North America, it has left high concentrations of lead in the dirt adjacent to all roads that were constructed prior to its phaseout. Child development specialists often advise parents to not let their children play in such dirt, especially because some children like to eat dirt (see Pica (disorder)).

Alternative antiknock agents Since the main problem with TEL is its lead content, many alternative additives that contain less poisonous metals have been examined. Methylcyclopentadienyl Manganese Tricarbonyl (MMT or methylcymantrene) is used as an antiknock agent in Canada, but its use as a fuel additive had been banned in the US until 1995. Ferrocene has also been reported as an effective antiknock agent. It had also been established by 1921 that ethanol was an effective antiknock agent, but TEL was introduced for mainly commercial reasons to replace it.

Improvements of the gasoline itself decrease the need for separate antiknock agents. Synthetic iso-octane and alkylate are examples of such blending stocks.

References "Countries where Leaded Petrol is Possibly Still Sold for Road Use of 17 countries in region, alphabetical and population order" By Elizabeth O'Brien collating data from The LEAD Group, Partnership for Cleaner Fuels & Vehicles (PCFV) & International Fuel Quality Center - http://www.lead.org.au/fs/fst27.html

See also

External links



Lead TetraEthyl and MTBE
Structure and importance as an additive to petroleum.

Tetra-ethyl lead - Wikipedia, the free encyclopedia
Tetra-ethyl lead, abbreviated TEL, is an organometallic compound with the formula (CH 3 CH 2) 4 Pb. Once a common anti-knock additive in gasoline (petrol), TEL usage was largely ...

Crest Environmental Services Tetra-Ethyl Lead and Decoking Specialists
Crest Environmental Decoking and Tetra-Ethyl Lead Specialists ... We are specialist in Tetra-Ethyl Lead and other organometallic compounds with expertise in using the world ...

AskOxford: tetraethyl lead
tetraethyl lead /tetr ee thil/ • noun Chemistry an oily organic compound of lead, used as an anti-knock agent in leaded petrol. Perform another search of the Compact Oxford ...

Definition: tetraethyl lead from Online Medical Dictionary
The Online Medical Dictionary is a searchable dictionary of definitions from medicine, science and technology.

Definition: lead tetraethyl from Online Medical Dictionary
The Online Medical Dictionary is a searchable dictionary of definitions from medicine, science and technology.

TETRAETHYLLEAD
Hazard Rankings More hazardous than most chemicals in 5 out of 5 ranking systems. Ranked as one of the most hazardous compounds (worst 10%) to ecosystems and human health.

tetraethyl lead definition of tetraethyl lead in the Free Online ...
tetraethyl lead (tĕt'rəĕth`əl), (C 2 H 5) 4 Pb, viscous, colorless, poisonous liquid. It is an organometallic compound prepared by reacting ethyl chloride with a sodium-lead ...

tetraethyl lead
Compound added to leaded petrol as a component of antiknock to increase the efficiency of combustion in car engines

Leaded gasoline: history and current situation
Ethyl" brand leaded gasoline-- tetra-ethyl lead -- loony gas -- one of the world's greatest environmental disasters. Many thousands died, and whole nations were ...

 

Tetra Ethyl Lead



 
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