Ethylene, or Ethene (CAS 74-85-1), is the simplest alkene, characterized by a carbon-carbon double bond (C=C). This structural feature imbues ethylene with a unique reactivity that forms the basis of its extensive industrial applications. Understanding its chemical properties and reaction pathways is fundamental to grasping its significance in organic chemistry and the broader chemical industry.

At room temperature and atmospheric pressure, ethylene exists as a colorless, flammable gas with a faint, sweet odor. Its molecular formula is C2H4, and its structure is planar, with all six atoms lying in the same plane and bond angles close to 120 degrees. This spatial arrangement is a direct consequence of the sp2 hybridization of the carbon atoms involved in the double bond.

The double bond in ethylene consists of one sigma (σ) bond and one pi (π) bond. The pi bond, formed by the lateral overlap of p-orbitals, is weaker and more accessible than the sigma bond, making it the primary site for chemical reactions. This electrophilic addition characteristic is central to ethylene's industrial utility.

One of the most industrially important reactions of ethylene is polymerization. Under specific conditions, using catalysts like Ziegler-Natta or metallocenes, ethylene monomers link together to form long polymer chains, creating polyethylene. The type of catalyst and reaction conditions determine the properties of the resulting polyethylene, from high-density (HDPE) to low-density (LDPE).

Ethylene readily undergoes addition reactions. For example, reacting ethylene with halogens like chlorine or bromine results in the formation of vicinal dihalides (e.g., 1,2-dichloroethane). Hydrogenation, the addition of hydrogen, converts ethylene to ethane. Hydration, the addition of water, catalyzed by acids, produces ethanol.

The oxidation of ethylene is another critical industrial process. Partial oxidation leads to ethylene oxide, a highly reactive intermediate used in the production of ethylene glycol, surfactants, and other chemicals. Further oxidation can yield acetaldehyde.

The agricultural use of ethylene relies on its function as a plant hormone, affecting processes like fruit ripening. This biological activity is a testament to the molecule's fundamental chemical nature, even though the mechanisms differ from typical industrial reactions.

For professionals working with ethylene, familiarity with its ethylene gas properties, including flammability limits and reactivity with various substances, is crucial for safe handling. While the 'buy ethylene online' market is robust, responsible procurement necessitates a thorough understanding of its chemical behavior.

In summary, the chemistry of ethylene, centered around its double bond, dictates its role as a versatile building block. Its ability to polymerize and undergo various addition and oxidation reactions makes it indispensable for producing plastics, fuels, and numerous other essential chemicals, underpinning much of modern industrial chemistry.