Tetraethyllead

Long ago, people put lead in gas.

This lead helped car engines run better. It made the fuel work more smoothly. It also helped parts inside the engine last longer.

But the lead was not safe. It could hurt people's brains. It was especially bad for children.

Because it was unsafe, many lands stopped using it. Most countries now use clean gas instead.

This change helps keep our air and soil clean. It helps keep all of us healthy.

For much of the 1900s, people added a chemical to gasoline. This chemical was called tetraethyllead, or TEL.

TEL helped car engines run much better. It acted as an antiknock agent. This means it stopped the fuel from burning too early or unevenly. This allowed engines to be more powerful and use fuel well. TEL also helped protect engine parts from wearing out too fast.

To make TEL work, it had to dissolve in the gas. Four ethyl groups helped the lead atom stay mixed in the fuel. When the engine got hot, the TEL broke apart. It left behind lead oxide. This helped control the flame so the engine ran smoothly.

But TEL was very dangerous. It is a neurotoxin, which means it can hurt the brain. It was especially harmful to children. It could also be absorbed easily by the body.

Because of these risks, countries began to stop using it. The United States started phasing it out in the 1970s. Most countries banned it by the early 2000s. In 2021, the sale of leaded gas for cars ended worldwide.

Tetraethyllead, or TEL, is a special chemical compound used in fuel. For much of the 20th century, it was a common additive in gasoline.

It was used to increase the octane rating of fuel. A higher octane rating allows an engine to use more compression. This makes the vehicle more powerful and helps it use fuel better. TEL was very useful for making cars and planes run more efficiently. However, it was also a very dangerous substance for people and the planet.

To understand how it works, we must look at the engine. TEL contains one lead atom and four ethyl groups. These groups help the lead dissolve into the gasoline. When the fuel enters the hot combustion chamber, the TEL breaks apart. It turns into lead, lead oxide, and ethyl radicals. The lead oxide acts as a scavenger. It stops a "cool flame" from starting too early. This ensures the fuel ignites at the perfect time for a smooth burn.

Scientists worked for a long time to find the right additive. The German chemist Carl Jacob Löwig first made TEL in 1853. Later, an American engineer named Thomas Midgley Jr. discovered its use in engines. He worked for General Motors and searched for a solution for six years. On December 9, 1921, he found that lead was the best choice. He tested about 33,000 different substances before finding TEL. It was effective because it only needed a very small amount to work.

There are many important facts about how much TEL was used. In the United States alone, about 20 trillion liters of leaded gas were sold between 1926 and 1985. This is equal to about 8 million tons of lead. Most of this lead was released into the air through engine exhaust. Researchers found that TEL is a neurotoxin, which means it can harm the brain. It is especially dangerous for children. Because it dissolves easily in fats, it can move through the body very quickly.

Today, the world has moved away from using TEL. Many countries began to stop using it in the 1970s. The United States finished removing it from road vehicles on January 1, 1996. Japan was the first country to ban it completely in 1986. Finally, the sale of leaded gasoline for cars ended all over the world in July 2021. This happened after Algeria stopped making it. Now, we use safer ways to make engines run well without hurting our health.

Tetraethyllead, often called TEL, is an organolead compound with the chemical formula Pb(C2H5)4. It served as a vital fuel additive for much of the 20th century.

By being mixed into gasoline, TEL increased the octane rating of the fuel. A higher octane rating allows an engine to use much higher compression. This process increases vehicle performance and improves overall fuel economy. For decades, it was a standard part of the global energy landscape.

To understand its mechanism, we must look at the chemistry inside a combustion chamber. TEL consists of one central lead atom surrounded by four ethyl groups. These ethyl groups are highly lipophilic, meaning they allow the lead to dissolve easily in petrol. When the fuel enters the hot engine, the TEL decomposes due to the heat. It breaks down into ethyl radicals, lead, and lead oxide. The lead oxide acts as a scavenger to inhibit a "cool flame." This is an unwanted, low-temperature combustion reaction that occurs before the main ignition. By quenching these radicals, the lead ensures the fuel ignites at the optimal time.

Because lead and lead oxide can build up and foul an engine, other chemicals were added. These additives, such as 1,2-dichloroethane and 1,2-dibromoethane, are known as scavengers. They work together to form volatile lead(II) chloride and lead(II) bromide. These substances allow the lead to be flushed out of the engine and into the exhaust air. This process prevented the accumulation of inorganic lead in the pistons. Without these scavengers, the lead would quickly damage the internal parts of the motor.

The history of TEL involves long periods of research and discovery. The German chemist Carl Jacob Löwig first synthesized the compound in 1853. Much later, American engineer Thomas Midgley Jr. discovered its effectiveness as an antiknock agent. Working for General Motors, Midgley spent six years searching for a solution. He screened approximately 33,000 different substances before finding lead on December 9, 1921. He found that lead was the most effective because it required the smallest concentrations. Only 1 part of TEL to 1,300 parts of gasoline by weight was needed to suppress detonation.

Despite its efficiency, the scale of its use had massive environmental consequences. Between 1926 and 1985, the United States alone sold an estimated 20 trillion liters of leaded gasoline. This volume contained about 8 million tons of inorganic lead. Most of this lead was released into the atmosphere through exhaust. Globally, it is estimated that more than 15 million tonnes of lead were released. Researchers in 2011 estimated the annual worldwide impact of TEL included 1.1 million excess deaths. It also contributed to 322 million lost IQ points and 4% of the global GDP.

Scientists eventually discovered that TEL is highly neurotoxic to the human brain. It is a central nervous system toxin that can cause acute toxic psychosis. Because the compound is so soluble in fats, it can easily pass through the blood-brain barrier. Once inside, lead ions accumulate in areas like the hippocampus and the frontal cortex. This makes it especially dangerous for children. While inorganic lead can sometimes be removed using chelating agents, there is no known cure for direct TEL poisoning. Treatments for TEL exposure are generally limited to supportive care.

The global phase-out of TEL was a long and complex process. Many countries began moving away from the additive in the 1970s. The rise of catalytic converters made TEL use impossible, as lead damages these emission-control devices. Japan was the first country to completely ban leaded gasoline in 1986. The United States achieved total elimination for on-road vehicles on January 1, 1996. Finally, in July 2021, the sale of leaded gasoline for cars ended worldwide. This followed the end of production in Algeria, prompting the United Nations to declare an official end to its use.