Ethylene

Ethylene, also known by its IUPAC name ethene, is a hydrocarbon with the formula C₂H₄ or H₂C=CH₂. It is a colourless, flammable gas that has a faint sweet and musky smell when pure. Ethylene is the simplest alkene, which means it is a hydrocarbon with carbon–carbon double bonds.

Ethylene is very important in the chemical industry. In 2022, over 225 million tonnes of it was made around the world, more than any other organic compound. Most of this ethylene is used to make polyethylene, a type of plastic made from long chains of ethylene units. Making ethylene can release greenhouse gases, such as methane from feedstock production and carbon dioxide from using non-sustainable energy.

Besides its use in industry, ethylene also plays a key role in nature. It acts as a plant hormone and is used in farming to help fruits ripen. When ethylene is combined with water, it forms ethanol.

Structure and properties

Ethylene is a type of hydrocarbon with four hydrogen atoms attached to two carbon atoms connected by a double bond. All six atoms in ethylene lie in the same flat plane, and the angle between the hydrogen and carbon atoms is about 117.4°, which is close to the perfect 120° angle.

The double bond in ethylene makes it reactive. This bond has a lot of electrons, so it can be affected by certain chemicals. Many of ethylene’s reactions happen with the help of special metals that temporarily attach to the molecule.

Production

Ethylene is made in large amounts around the world. In 2011, about 141 million tonnes were produced, and by 2013, at least 117 companies in 32 countries were making it. To keep up with growing demand, many new factories were built, especially in the Mideast and China.

Ethylene is made in factories using different methods. One common way is called steam cracking, where hydrocarbons and steam are heated very hot to break them into smaller pieces. This makes ethylene from ethane. In Europe and Asia, ethylene is often made from naphtha, gasoil, and condensates. Other methods include Fischer-Tropsch synthesis and methanol-to-olefins.

Uses

Ethylene is a very useful gas in factories. It is mostly used to make plastics, like the kind used for bags and bottles. It can also be changed into other chemicals that help make cleaning products and car fluids.

Ethylene is also important for plants. It helps them grow and can be used to keep fruits fresh longer by stopping them from ripening too quickly.

Ligand

Ethylene can act as a special kind of helper in chemical reactions with metals. One famous example is called Zeise’s salt, which includes ethylene. Other important chemicals with ethylene are used to make propionaldehyde, a substance made in factories.

History

Some geologists think that a famous Greek prophetess may have felt strange because of a gas called ethylene coming up from the ground.

Ethylene was first made by heating a type of alcohol with a strong acid. Scientists studied its properties and found it could mix with another gas to make a special oil. Later, the name "ethylene" was used for this gas, though today it is also called "ethene." It was once used as a way to help people sleep, but is not used much anymore because it has a strong smell and can be dangerous.

Safety

Like all hydrocarbons, ethylene can catch fire easily. It is also important to be careful around it because it can displace air and make it hard to breathe. Scientists have studied it and found no proof that it causes cancer in people.