Tetraethyllead

Tetraethyllead (TEL) is an organolead compound with the formula (CH₃CH₂)₄Pb. It was once widely used as an additive in gasoline (petrol) to increase its octane rating, which helps to prevent engine knocking and improve fuel efficiency. However, due to concerns over its toxicity and its ability to cause environmental pollution, the use of TEL in gasoline has been phased out in most countries.

History

TEL was first synthesized in 1887 by the German chemist Charles Friedel and the American engineer James Crafts. However, its anti-knock properties were not discovered until the 1920s by the General Motors research team, led by Thomas Midgley Jr.. Its widespread use in gasoline began in the 1920s and continued for several decades.

Chemical Properties

Tetraethyllead is a colorless, oily liquid at room temperature. It is poorly soluble in water but mixes well with organic solvents and gasoline. The compound is stable under normal conditions but decomposes upon heating, producing toxic fumes including lead and lead oxides.

Health and Environmental Impact

The use of TEL in gasoline has raised significant health and environmental concerns. Lead is a potent neurotoxin that can cause a range of health issues, particularly in children, including cognitive impairment and developmental delays. The combustion of TEL-laden gasoline releases lead into the atmosphere, from where it can be inhaled or deposited onto soil and water bodies, further contributing to environmental lead contamination.

Regulation and Phase-out

Due to these concerns, many countries began to regulate and eventually ban the use of TEL in gasoline starting in the 1970s. The United States began phasing out leaded gasoline in 1973, with a complete ban coming into effect in 1996. Similar bans have been implemented worldwide, significantly reducing the global use of TEL.

Current Use

Today, TEL is still used in some specialized applications, such as in racing fuels and in some aviation gasolines (avgas) for piston-engine aircraft. However, these uses are highly regulated, and efforts are ongoing to find safer alternatives.

See Also

• Lead poisoning
• Environmental pollution
• Octane rating
• Gasoline