Ethylene

Some gas helps fruit grow.

This gas makes fruit ripe. It is a natural part of plants.

People also use this gas for many things. It helps make plastic. We use this plastic for grocery bags.

It is also used for trash bags.

This gas has a sweet smell. It can also catch fire easily.

Making this gas can release air that warms the Earth.

It is a very busy gas in our world.

Ethylene is a clear gas. It has a sweet smell.

It is also very flammable. This means it can catch fire easily.

In nature, ethylene is a hormone. A hormone is a natural signal for plants. This gas tells fruit to ripen. It also helps plants grow flowers.

People make a lot of ethylene. They make over 225 million tonnes every year. Most of it is used to make plastic. We call this plastic polyethylene. It is used for many things. You might see it in grocery bags or trash liners.

Factories make ethylene in many ways. One way is called steam cracking. They heat oils or gases to very high heat. This heat breaks large parts into smaller ones. This makes ethylene. Making this gas can release carbon dioxide. This is a gas that warms the Earth.

Scientists also use ethylene in labs. It can be used as an anesthetic. An anesthetic is a gas that helps people sleep during surgery. But it is not used much now. It can be hard to control.

Ethylene is a clear, flammable gas with a faint, sweet, and musky smell. It is a simple hydrocarbon, which is a molecule made of carbon and hydrogen atoms. Specifically, it is the simplest alkene, meaning it contains a carbon-carbon double bond. This double bond is very important because it makes the molecule reactive. This reactivity allows ethylene to be used in many different ways. It is one of the most important chemicals in the world today. In 2022, the world produced over 225 million tonnes of it. This amount is larger than the production of any other organic compound.

There are several ways that factories make ethylene. One main method is called steam cracking. In this process, workers heat hydrocarbons and steam to very high temperatures between 750 and 950 degrees Celsius. This intense heat breaks large molecules into smaller ones. When ethane is used as the starting material, ethylene is the result. After the cracking happens, the ethylene is separated through compression and distillation. In places like Europe and Asia, it is often made by cracking substances like naphtha or gasoil. Other methods include the Fischer-Tropsch synthesis or the methanol-to-olefins process.

People have been studying this gas for a very long time. Johann Joachim Becher is thought to have discovered it by heating ethanol with sulfuric acid. He wrote about it in his book in 1669. Later, in 1795, four Dutch chemists studied its properties. They found it was different from hydrogen gas and contained carbon. They even called it "olefiant gas" because it could make oil.

This old name is actually where the modern word "olefin" comes from.

Ethylene is used to create many things we see every day. More than half of the world's supply goes toward making polyethylene. This is the most widely used plastic in the world. You might find it in plastic films, carrier bags, or trash liners.

It is also used to make ethylene oxide and ethylbenzene. These chemicals help create things like detergents, antifreeze, and even rubber for tires. Some of these processes use a catalyst, which is something that helps a chemical reaction happen.

In nature, ethylene works as a very important plant hormone. A hormone is a natural signal that tells a living thing what to do. In plants, ethylene helps fruits ripen and helps flowers grow.

Farmers use this knowledge to control how fresh fruit stays in stores. In the past, ethylene was even used as an anesthetic to help people sleep during surgery. However, it is not used much for that now because it can be explosive. It is a fascinating molecule that connects tiny plants to huge global industries.

Ethylene, also known by its IUPAC name ethene, is a colorless and highly flammable gas. It possesses a faint, sweet, and musky odor when it is in a pure state. Chemically, ethylene is a hydrocarbon, which is a molecule composed of carbon and hydrogen atoms. It is classified as the simplest alkene. An alkene is a type of hydrocarbon that contains at least one carbon-carbon double bond. This double bond is a critical feature of the molecule. It creates a region of high electron density. This density makes the molecule very reactive, meaning it easily undergoes chemical changes.

The structure of ethylene is quite simple and elegant. It consists of four hydrogen atoms bound to two carbon atoms. These two carbon atoms are connected by a double bond. All six atoms in the molecule lie on the same flat plane. The angle between the hydrogen and carbon atoms is 117.4 degrees. This is very close to the ideal 120-degree angle for its specific atomic arrangement. The double bond is also somewhat weak. If you supply heat at 50 degrees Celsius, the bond can rotate. This rotation requires breaking the pi-bond, which is one part of the double bond. This specific pi-bond is what makes ethylene so useful in chemical reactions.

Industrial production of ethylene happens on a massive scale. In 2022, global production exceeded 225 million tonnes. This makes it the most produced organic compound in the world. One primary method for making it is called steam cracking. In this process, hydrocarbons and steam are heated to temperatures between 750 and 950 degrees Celsius. This intense heat breaks large hydrocarbon molecules into smaller ones. If ethane is used as the starting material, ethylene is produced. In Europe and Asia, producers often crack naphtha, gasoil, or condensates. This method also produces other useful chemicals like propylene. After cracking, the ethylene is separated from the mixture using compression and distillation. Other methods include methanol-to-olefins and Fischer-Tropsch synthesis.

Ethylene is used to create a vast array of essential products. The largest use is polymerization, which accounts for more than half of the global supply. Through polymerization, ethylene is turned into polyethylene. Polyethylene is the most widely used plastic on Earth. It is used to make packaging films, carrier bags, and trash liners. Another major use is oxidation. This process creates ethylene oxide, a key material for making detergents and surfactants. Ethylene oxide can also be turned into ethylene glycol, which is used as automotive antifreeze.

Other chemical reactions involve ethylene in several different ways. Through halogenation, ethylene reacts with halogens to create intermediates like ethylene dichloride. This chemical is a precursor to polyvinyl chloride, a common plastic. Alkylation is another process that produces ethylbenzene. Ethylbenzene is used to make styrene, which is used for insulation and polystyrene packaging. Styrene is also used to make the rubber found in tires and footwear.

Ethylene can also undergo hydration to produce ethanol. Since the mid-1990s, this has been done using direct hydration with solid acid catalysts. Even more specialized reactions, like the oxo reaction, produce propionaldehyde for various industrial uses.

Humans have been discovering the properties of ethylene for centuries. Johann Joachim Becher is believed to have discovered the gas in 1669. He produced it by heating ethanol with sulfuric acid. In 1795, a group of four Dutch chemists studied the gas in detail. They discovered it contained both carbon and hydrogen. They also found it could produce oil when combined with chlorine. Because of this, they called it "olefiant gas." This name is the origin of the modern term "olefin."

The name ethylene itself became common by 1852. While the official IUPAC name is ethene, the name ethylene remains very popular in the North American chemical industry.

Beyond the factory, ethylene plays a vital role in the natural world. It acts as a natural plant hormone. This means it serves as a chemical signal that tells plants how to grow. Ethylene specifically controls the ripening of fruits and the flowering of plants. In agriculture, farmers use ethylene to manage how quickly fruit ripens. Conversely, they can use "scrubbing" to remove ethylene and delay ripening to keep fruit fresh longer. In a much more specialized niche, ethylene was once used as an anesthetic. Researchers at the University of Chicago studied its use for this purpose. However, because it is explosive and has a pungent odor, it is rarely used as an anesthetic today. Ethylene remains a fundamental link between biology and global industry.