Tetra-ethyl lead

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Tetraethyl lead

−136 °C

84.5±0.5 °C (15 mmHg)

Tetraethyllead (common name tetraethyl lead), abbreviated TEL, is an organolead compound with the formula (CH3CH2)4Pb. Once a common antiknock additive/octane booster in gasoline (petrol), TEL usage was largely discontinued because of the toxicity of lead and its deleterious effect on catalytic converters. It is still used as an additive in aviation fuel for piston engine-powered aircraft.

Contents

Synthesis and properties

TEL is produced by reacting chloroethane with a sodiumlead alloy.[2]

Despite decades of research, no reactions were found to improve upon this rather difficult process that involves metallic sodium—a process with lithium was developed, but never put into practice. A related compound, tetramethyllead, was commercially produced by a different electrolytic reaction.[2] The product, TEL, is a viscous colorless liquid. Because TEL is charge neutral and contains an exterior of alkyl groups, it is highly lipophilic and soluble in petrol (gasoline).

Reactions

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 completely into lead and lead oxides and combustible, short-lived ethyl radicals. Lead and lead oxide scavenge radical intermediates in combustion reactions. This prevents ignition of unburnt fuel during the engine's exhaust stroke.[2] Lead itself is the reactive antiknock agent, and TEL serves as a gasoline-soluble lead carrier.[2] When (CH3CH2)4Pb burns, it produces not only carbon dioxide and water, but also lead:

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