Ethylene

Ethylene, a colorless, flammable gas with a slightly sweet odor, is both a natural product and an important industrial chemical. Its molecular formula is C2H2.

Ethylene occurs naturally in small amounts in plants where it functions as a plant hormone. Many fruits and vegetables, especially citrus fruit and tomatoes, release ethylene as they ripen. The released ethylene triggers futher ripening.

The commercial fruit industry uses to advantage this ripening function for ethylene. Crops, such as bananas and tomatoes, are picked green to prevent spoiling and bruising during transportation to markets. At its destination, the fruit is exposed to ethylene gas, which stimulates the ripening process; 1kg of tomatoes can be ripened by exposure to 0.1 mg of ethylene.

Industrially, U.S. chemical manufacturers produce more ethylene each year than any other compound except sulfuric acid. The ethylene does not reach consumers directly; most of it goes into the production of plastics and synthetic fibers. Almost half of the ethylene produced is consumed in the production of the well-known plastic called polyethylene.

[source: Chemical Principles by H. Stephen Stoker]