Ethylene is part of the hydrocarbon group of organic compounds, so called because they are made up of just hydrogen and carbon. The principle source of hydrocarbons is crude oil, which comprises a range of hydrocarbons from the light compounds such as methane, ethane and ethylene up to heavy, long-chain carbon compounds such as asphalt and bitumen. Although ethylene occurs in crude oil, most of it is produced by splitting up the long chain compounds using a process called cracking.
Both ethylene and hydrogen exist at room temperature as gases, however nothing happens when these two gases are mixed. However, the addition of a catalyst leads to the rapid hydrogenation of the ethylene to form ethane in a process called catalytic hydrogenation. Effective catalysts for this process include platinum, palladium and nickel. These metals are often supported on activated charcoal. Catalytic hydrogenation is an example of heterogeneous catalysis, as the reactants and the catalyst are in different phases. The only use of ethylene hydrogen is in the production of ethane, however many other useful products can be synthesized by reacting different compounds with ethylene.
The conversion of ethylene to ethane is not especially useful in organic chemistry. Ethylene is a versatile and reactive compound, but in comparison, ethane is quite dull. Ethane is mostly unreactive and its main use is as a fuel as it readily reacts with oxygen to generate heat. Addition of other compounds across the ethylenic bond creates a range of useful products, including alcohols and haloalkanes. Various types of haloalkanes can be used as solvents, refrigerants, fire retardants and aerosol propellants.
Ethylene is part of a group of organic compounds called alkylenes. Alkylenes are characterized by containing a carbon-carbon double bond. Alkylenes, such as ethylene, can be made to react with themselves to form compounds with thousands of repeating units. This process is called polymerization. This discovery led to the emergence of a brand new branch of chemistry, called polymer chemistry. Furthermore, it led to the development of a completely new type of material that has revolutionized the whole world. Adding a special kind of catalyst called an initiator to ethylene causes its double bonds to join together to form polyethylene, also known as polythene. Polyethylene is used in everything from food packaging to electrical insulation and water piping.