User:Milton Beychok/Sandbox: Difference between revisions

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'''Tetraethyl lead''' (TEL) is a viscous liquid with the chemical formula (CH<sub>3</sub>CH<sub>2</sub>)<sub>4</sub>Pb. Once widely used (circa 1925 to 1990) to increase the [[octane rating]] of [[gasoline]] ([[petrol]]), TEL usage in gasoline has been largely phased out by most nations<ref>
http://www.uneptie.org/energy/transport/documents/pdf/phasingLead.pdf Phasing Lead Out of Gasoline] A report issued by the [[United Nations Environmental Programme]] (UNEP). See page 8 of 23 pdf pages.</ref>primarily because of the toxicity of the [[lead]] [[emission]]s from spark-ignited [[internal combustion engines]] burning gasoline containing TEL. Another reason for discontinuing TEL usage was that it degraded the efficiency of the [[catalytic converters]] installed in automotive vehicles to reduce their emissions of [[Air pollution|air pollutant]]s.
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| align="left"|'''Common name'''|| align="left"|tetraethyl lead
| align="left"|'''Common name'''|| align="left"|tetraethyl lead
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| align="left"|'''Other names'''|| align="left"|tetra-ethyl lead, lead tetraethyl,<br/>tetraethyl plumbane
| align="left"|'''Other names'''|| align="left"|tetra-ethyl lead, lead tetraethyl,<br/>tetraethyl plumbane, TEL
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'''Tetraethyl lead''' (TEL) is a viscous liquid with the chemical formula (CH<sub>3</sub>CH<sub>2</sub>)<sub>4</sub>Pb. Once widely used (circa 1925 to 1990) to increase the [[octane rating]] of [[gasoline]] ([[petrol]]), TEL usage in gasoline has been largely phased out by most nations<ref>
http://www.uneptie.org/energy/transport/documents/pdf/phasingLead.pdf Phasing Lead Out of Gasoline] A report issued by the [[United Nations Environmental Programme]] (UNEP). See page 8 of 23 pdf pages.</ref>primarily because of the toxicity of the [[lead]] [[emission]]s from spark-ignited [[internal combustion engines]] burning gasoline containing TEL. Another reason for discontinuing TEL usage was that it degraded the efficiency of the [[catalytic converters]] installed in automotive vehicles to reduce their emissions of [[Air pollution|air pollutant]]s.
==Manufacture and properties==
==Manufacture and properties==


Tetraethyl lead is produced by the alkylation of a [[sodium]]-[[lead]] [[alloy]] using [[chloroethane]] as expressed by this chemical equation:
TEL is produced by the alkylation of a [[sodium]]-[[lead]] [[alloy]] using [[chloroethane]] as expressed by this chemical equation:


:4 CH<sub>3</sub>CH<sub>2</sub>Cl + 4 NaPb →  (CH<sub>3</sub>CH<sub>2</sub>)<sub>4</sub>Pb + 4 NaCl + 3 Pb
:4 CH<sub>3</sub>CH<sub>2</sub>Cl + 4 NaPb →  (CH<sub>3</sub>CH<sub>2</sub>)<sub>4</sub>Pb + 4 NaCl + 3 Pb
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The product tetraethyl lead is a [[Viscosity|viscous]] colorless liquid that is highly [[Lipophilicity|lipophilic]] and soluble in fats, oils and [[lipids]] as well as gasoline and other [[non-polar]] [[hydrocarbon]]s. Other properties of tetraethyl lead are listed in the adjacent table.
The product tetraethyl lead is a [[Viscosity|viscous]] colorless liquid that is highly [[Lipophilicity|lipophilic]] and soluble in fats, oils and [[lipids]] as well as gasoline and other [[non-polar]] [[hydrocarbon]]s. Other properties of tetraethyl lead are listed in the adjacent table.


At the temperatures found in spark-ignited [[internal combustion engine]]s, tetraethyl lead decomposes completely into lead and [[lead oxide]] (PbO) and combustible, short-lived ethyl [[Radical (chemistry)|radical]]s. Lead itself is the reactive agent that enhances the octane rating of gasolines and tetraethyl lead serves as a gasoline-soluble lead carrier.  
At the temperatures found in spark-ignited [[internal combustion engine]]s, TEL decomposes completely into lead and [[lead oxide]] (PbO) and combustible, short-lived ethyl [[Radical (chemistry)|radical]]s. Lead itself is the reactive agent that enhances the octane rating of gasolines and tetraethyl lead serves as a gasoline-soluble lead carrier.  


==TEL fluid==
==TEL fluid formulation==


When tetraethyl lead burns, it produces not only [[carbon dioxide]] (CO<sub>2</sub>) and [[water]] (H<sub>2</sub>O), but also lead (Pb):
When tetraethyl lead burns, it produces not only [[carbon dioxide]] (CO<sub>2</sub>) and [[water]] (H<sub>2</sub>O), but also lead (Pb):
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: (CH<sub>3</sub>CH<sub>2</sub>)<sub>4</sub>Pb  +  13 O<sub>2</sub>  →  8 CO<sub>2</sub>  +  10 H<sub>2</sub>O  +  Pb
: (CH<sub>3</sub>CH<sub>2</sub>)<sub>4</sub>Pb  +  13 O<sub>2</sub>  →  8 CO<sub>2</sub>  +  10 H<sub>2</sub>O  +  Pb


The lead can the oxidize further to give species such as [[lead oxide]] (PbO):
The lead can the oxidize further to give [[lead oxide]] (PbO):


: 2 Pb  + O<sub>2</sub> → 2 PbO
: 2 Pb  + O<sub>2</sub> → 2 PbO


The Pb and PbO would quickly accumulate and destroy an engine. For this reason, the lead scavengers [[1,2-Dibromoethane|1,2-dibromoethane]] and [[1,2-Dichloroethane|1,2-dichloroethane]] are used in conjunction with TEL.
The Pb and PbO would quickly accumulate and destroy an engine. For this reason, the TEL used in gasoline was actually part of a formulated liquid fluid known as ''TEL fluid'' or ''ethyl fluid'' that contained [[1,2-Dibromoethane|1,2-dibromoethane]] and [[1,2-Dichloroethane|1,2-dichloroethane]] liquids which served to scavenge the Pb and PbO from the engine.  


==References==
==References==
{{reflist}}
{{reflist}}

Revision as of 00:06, 15 May 2009

Tetraethyl lead (TEL) is a viscous liquid with the chemical formula (CH3CH2)4Pb. Once widely used (circa 1925 to 1990) to increase the octane rating of gasoline (petrol), TEL usage in gasoline has been largely phased out by most nations[1]primarily because of the toxicity of the lead emissions from spark-ignited internal combustion engines burning gasoline containing TEL. Another reason for discontinuing TEL usage was that it degraded the efficiency of the catalytic converters installed in automotive vehicles to reduce their emissions of air pollutants.

Properties
Property Value
Common name tetraethyl lead
Other names tetra-ethyl lead, lead tetraethyl,
tetraethyl plumbane, TEL
IUPAC name
CAS number 78-00-2
Molecular formula (CH3CH2)4Pb
Molecular mass 323.4 g/mol[2]
Density 1.653 g/ml for liquid at 20 °C, 1 atm
Boiling point 455.7 K (182.6 °C) at 1 atm[2]
Melting point 142.94 K (-130.2 °C)[2]
Specific heat, cp 0.956 J/(g·K) for liquid at 20 °C[2]
Heat of vaporization 175.0 J/g for liquid at 182.6 °C[2]
Heat of fusion 27.2 J/g for solid at -130.2 °C[2]
Viscosity
Refractive index

Manufacture and properties

TEL is produced by the alkylation of a sodium-lead alloy using chloroethane as expressed by this chemical equation:

4 CH3CH2Cl + 4 NaPb → (CH3CH2)4Pb + 4 NaCl + 3 Pb

which can also be written as:

4 mols of chloroethane + 4 mols of sodium-lead alloy → 1 mol of tetraethyl lead + 4 mols of sodium chloride + 3 mols of lead

The product tetraethyl lead is a viscous colorless liquid that is highly lipophilic and soluble in fats, oils and lipids as well as gasoline and other non-polar hydrocarbons. Other properties of tetraethyl lead are listed in the adjacent table.

At the temperatures found in spark-ignited internal combustion engines, TEL decomposes completely into lead and lead oxide (PbO) and combustible, short-lived ethyl radicals. Lead itself is the reactive agent that enhances the octane rating of gasolines and tetraethyl lead serves as a gasoline-soluble lead carrier.

TEL fluid formulation

When tetraethyl lead burns, it produces not only carbon dioxide (CO2) and water (H2O), but also lead (Pb):

(CH3CH2)4Pb + 13 O2 → 8 CO2 + 10 H2O + Pb

The lead can the oxidize further to give lead oxide (PbO):

2 Pb + O2 → 2 PbO

The Pb and PbO would quickly accumulate and destroy an engine. For this reason, the TEL used in gasoline was actually part of a formulated liquid fluid known as TEL fluid or ethyl fluid that contained 1,2-dibromoethane and 1,2-dichloroethane liquids which served to scavenge the Pb and PbO from the engine.

References

  1. ↑ http://www.uneptie.org/energy/transport/documents/pdf/phasingLead.pdf Phasing Lead Out of Gasoline] A report issued by the United Nations Environmental Programme (UNEP). See page 8 of 23 pdf pages.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 NIST Chemistry WebBook
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