ethylene

—ethylenic /eth'euh lee"nik, -len"ik/, adj.

/eth"euh leen'/, Chem.

adj.

1. containing the ethylene group.

n.

2. Also called ethene, olefiant gas. a colorless, flammable gas, C₂H₄, having a sweet, unpleasant odor and taste, the first member of the ethylene series, usually obtained from petroleum and natural gas: used as an agent to improve the color of citrus fruits, in the synthesis of polyethylene, ethylene dibromide, ethylene oxide, and other organic compounds, and in medicine chiefly as an inhalation anesthetic.

[1850-55; ETHYL + -ENE]

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Simplest olefin (CH₂CH₂), a colourless, flammable gas with a sweetish taste and odour.

The petrochemical having the highest volume, it occurs in petroleum and natural gas but is usually produced by heating higher hydrocarbons (usually ethane and ethane-propane mixtures). Ethylene is polymerized to polyethylene either at high pressures and temperatures or by catalysis. It reacts with numerous other chemicals to produce ethanol, solvents, gasoline additives, antifreeze, detergents, and various plastics. In plants, ethylene is a hormone that inhibits growth and promotes leaf fall and fruit ripening.

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▪ chemical compound

      the simplest of the organic compounds (organic compound) known as alkenes, which contain carbon-carbon double bonds. It is a colourless, flammable gas having a sweet taste and odour. Natural sources of ethylene include both natural gas and petroleum; it is also a naturally occurring hormone in plants (plant), in which it inhibits growth and promotes leaf fall, and in fruits (fruit), in which it promotes ripening.

      Ethylene is an important industrial organic chemical. It is produced by heating either natural gas, especially its ethane and propane components, or petroleum to 800–900 °C (1,470–1,650 °F), giving a mixture of gases from which the ethylene is separated. The melting point of ethylene is −169.4 °C [−272.9 °F], and its boiling point is −103.9 °C [−155.0 °F].

 Ethylene use falls into two main categories: 1) as a monomer, from which longer carbon chains are constructed, and 2) as a starting material for other two-carbon compounds. The first of these is the single largest use of ethylene, consuming about one-half of the annual output. polymerization (the repetitive joining of many small molecules (molecule) into larger ones) of ethylene gives polyethylene, a polymer having many uses, particularly in the production of packaging films, wire coatings, and squeeze bottles. When polymerization is carried out at high pressures and temperatures, the product is called low-density polyethylene and has properties different from the high-density polyethylene formed by polymerization under Ziegler-Natta catalytic conditions (see industrial polymers (industrial polymers, chemistry of)). Another use of ethylene as a monomer is in the formation of linear α-olefins (olefin). The oligomerization catalysts are similar to the Ziegler-Natta polymerization catalysts. Linear α-olefins have a number of applications, including the preparation of linear low-density polyethylene.

      Ethylene is the starting material for the preparation of a number of two-carbon compounds including ethanol (ethyl alcohol) (industrial alcohol), ethylene oxide (converted to ethylene glycol for antifreeze and polyester fibres and films), acetaldehyde (converted to acetic acid), and vinyl chloride (converted to polyvinyl chloride). In addition to these compounds, ethylene and benzene combine to form ethylbenzene, which is dehydrogenated to styrene for use in the production of plastics (plastic) and synthetic rubber.

Francis A. Carey

 

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