Ethylene is an Organic Compound and it is a colorless gas widely recognized for its simple structure and significant role in the natural world and industry. It is a hydrocarbon, which means it is made up of hydrogen and carbon atoms, specifically with the chemical formula C₂H₄. This compound is particularly notable for being the smallest alkene, which is a type of hydrocarbon with a carbon-carbon double bond in its structure. In nature, plants produce ethylene as a hormone that influences growth and development, such as the ripening of fruits. Industrially, ethylene is crucial in the production of plastics, antifreeze, and other synthetic materials. Its applications make it a fundamental substance in both biological and manufacturing processes.

What is Ethylene?

Ethylene is a colorless gas with the chemical formula C₂H₄, making it the simplest alkene — a type of hydrocarbon characterized by at least one carbon-carbon double bond. This gas is naturally produced by plants and acts as a hormone to regulate their growth and development, including the ripening of fruits. Beyond its biological role, ethylene is heavily used in various industries, primarily in the synthesis of plastics, such as polyethylene, and other important chemicals. Its versatility and widespread use in both nature and industry highlight its importance as a fundamental chemical compound.

Chemical Names And Formulas

Property	Value
Formula	CH₂=CH₂
Hill Formula	C₂H₄
Name	Ethylene
Alternate Names	Acetene, Elayl, Ethene, Freon 1150, Olefiant Gas, R-1150

Structure of Ethylene

Ethylene, with its chemical formula C₂H₄, features a straightforward molecular structure consisting of two carbon atoms double-bonded to each other. Each carbon atom is also bonded to two hydrogen atoms. This configuration forms a flat, planar molecule, which is characteristic of alkenes—the family of hydrocarbons that ethylene belongs to. The double bond between the carbon atoms is key to ethylene’s reactivity and is crucial for its role in chemical synthesis and biological functions. Understanding this structure helps explain why ethylene is so effective in processes like fruit ripening and the production of plastics.

Preparation of Ethylene

Ethylene can be produced through several methods, but one common laboratory method is the dehydration of ethanol by heating it in the presence of an acid catalyst like sulfuric acid. This process involves heating ethanol with a concentrated acid, which acts to remove water (H₂O) from the ethanol molecule, leaving ethylene. The chemical equation for this reaction is:

C₂H₅OH → C₂H₄ + H₂O =H₂SO₄

In industrial settings, C₂H₄ (Ethylene) is primarily produced by the steam cracking process where hydrocarbons such as ethane and propane are heated to high temperatures. This breaks the larger molecules down into simpler molecules like C₂H₄ (Ethylene). This method is highly efficient and accounts for the majority of ethylene produced globally, which is then used to manufacture a variety of chemical products and materials.

Physical Properties of Ethylene

Property	Description
Phase at Room Temperature	Gas
Color	Colorless
Odor	Slightly sweet
Density	Lighter than air, 1.178 kg/m³ (at 0°C and 1 atm)
Boiling Point	-103.7°C
Melting Point	-169.2°C
Solubility in Water	Slightly soluble
Flammability	Highly flammable

Chemical Properties of Ethylene

Reactivity with Halogens

• Ethylene easily reacts with halogens to form halogenated compounds. For instance, when C₂H₄ reacts with Cl₂, it forms dichloroethane. This reaction is used in adding elements across the double bond of the alkene.
• Equation: C₂H₄ + Cl₂ → C₂H₄Cl₂

Combustion

• Ethylene burns in the presence of oxygen to produce carbon dioxide and water and releases a significant amount of energy.
• Equation: C₂H₄ + 3O₂ → 2CO₂ + 2H₂O

Polymerization

• One of the most commercially significant properties of ethylene is its ability to polymerize, forming long chains called polyethylene, a common plastic. The reaction can be catalyzed by heat and pressure or specific catalysts. This process produces various types of polyethylenes used in different applications based on the conditions and catalysts used.
• Equation: nC₂H₄ → (C₂H₄)n

Addition Reactions

• As an alkene, ethylene can undergo addition reactions, where atoms or groups are added to the carbon atoms of the double bond. For example, adding water in the presence of an acid catalyst yields ethanol.
• Equation: C₂H₄ + H₂O → C₂H₅OH

Ethylene (C₂H₄) Chemical Compound Information

Chemical Identifiers

Identifier	Number/ID
CAS registry number	74-85-1
Beilstein number	1730731
PubChem compound ID	6325
PubChem substance ID	24857774
SMILES identifier	C=C
InChI identifier	InChI=1/C2H4/c1-2/h1-2H2
RTECS number	KU5340000
MDL number	MFCD00008604

NFPA Label

Property	Value
NFPA health rating	1
NFPA fire rating	4
NFPA reactivity rating	0

Uses of Ethylene

Ripening Agent in Agriculture

Ethylene is widely used in agriculture to regulate the ripening of fruits. By controlling the application of ethylene, farmers and distributors can ensure fruits such as bananas, tomatoes, and apples reach peak ripeness at the right time, enhancing flavor and texture for consumers.

Manufacturing of Plastics

One of the most significant uses of ethylene is in the production of polyethylene, one of the most common plastics used today. This plastic is utilized in products ranging from plastic bags and containers to more durable items like pipes and fittings.

Production of Industrial Chemicals

Ethylene is a key raw material for producing other chemicals including ethylene oxide and ethylene glycol. Ethylene oxide is crucial in making antifreeze and detergents, while ethylene glycol is used in the production of polyester fibers and resin.

Stimulating Plant Processes

In horticulture, ethylene is used to stimulate various plant processes such as flowering and the shedding of leaves. This application helps in managing the life cycle of plants more effectively in commercial nurseries and gardens.

Medical Applications

Ethylene is also used in the medical field, particularly in the synthesis of medical products like sterilization agents. Ethylene oxide is used to sterilize surgical instruments and supplies that cannot withstand high temperatures. They are free from microbes without damage.

FAQs

Is Ethylene Toxic to Humans?

Ethylene is generally non-toxic at low concentrations but can pose health risks at high levels, causing dizziness and nausea.

Why is Ethylene Banned?

Ethylene is not banned; however, its use is regulated due to its flammability and potential health effects at high concentrations.

Does Ethylene Smell?

Ethylene is essentially odor less to humans. However, it has a faintly sweet smell at very high concentrations, which is rarely detectable.