Ethylene
[CAS# 74-85-1]

Identification

• Classification: Organic raw materials >> Hydrocarbon compounds and their derivatives >> Acyclic hydrocarbon
• Name: Ethylene
• Synonyms: Ethene
• Molecular Formula: C₂H₄
• Molecular Weight: 28.05
• CAS Registry Number: 74-85-1
• EC Number: 200-815-3
• SMILES: C=C

Properties

• Density: 0.5±0.1 g/cm³ Calc.^*
• Melting point: -169 ºC (Expl.), -169 ºC (Expl.)
• Boiling point: -103.7±7.0 ºC 760 mmHg (Calc.)^*, -104 ºC (Expl.)
• Flash point: -125.1±13.0 ºC (Calc.)^*, -100 ºC (Expl.)
• Index of refraction: 1.295 (Calc.)^*

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS02;GHS04;GHS07 DangerGHS02
• Hazard Statements: H220:-H336:
• Precautionary Statements: P203-P210-P222-P261-P271-P280-P304+P340-P319-P377-P381-P403-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Flammable gases	Flam. Gas	1	H220
Specific target organ toxicity - single exposure	STOT SE	3	H336
Gases under pressure (compressed)	Press. Gas (Comp.)		H280
Gases under pressure (liquid)	Press. Gas (Liq.)		H280
Gases under pressure (refrigerated liquid)	Press. Gas (Ref. Liq.)		H281
Specific target organ toxicity - single exposure	STOT SE	3	H335
Specific target organ toxicity - single exposure	STOT SE	2	H336

• Transport Information: UN 1962

Discovory and Applicatios

Ethylene, also known by its IUPAC name ethene, is the simplest alkene with the chemical formula C₂H₄. It consists of two carbon atoms connected by a double bond, with each carbon also bonded to two hydrogen atoms. The molecule is planar and has a trigonal planar geometry around each carbon atom due to the sp² hybridization. Ethylene is a colorless gas at room temperature with a faint sweet odor and is highly flammable.

The discovery of ethylene dates back to the late 18th century. It was first identified in 1795 by the Dutch chemist Jan Baptist van Helmont, though its structure and properties were not fully understood at the time. The modern understanding of ethylene’s chemical structure emerged in the 19th century with the development of organic chemistry and the concept of unsaturation in hydrocarbons. Its importance rapidly grew as both a subject of scientific study and an industrial material.

Ethylene is a fundamental building block in the petrochemical industry. It is primarily produced by steam cracking of hydrocarbons such as ethane, propane, or naphtha. In this process, hydrocarbon feedstocks are heated in the presence of steam, breaking down large molecules into smaller ones, including ethylene. Ethylene production is one of the largest volume chemical processes in the world, reflecting its essential role in industrial chemistry.

One of ethylene’s most significant applications is in the production of polyethylene, the most widely used plastic globally. Polyethylene is formed through polymerization of ethylene monomers under high pressure or in the presence of catalysts such as Ziegler-Natta or metallocene catalysts. Polyethylene is used in packaging materials, containers, films, and many everyday plastic products.

Ethylene is also used as a precursor in the manufacture of other important chemicals, including ethylene oxide, ethylene dichloride, and styrene. Ethylene oxide is used to produce ethylene glycol, which is a key component of antifreeze and polyester fibers. Ethylene dichloride is an intermediate in the production of polyvinyl chloride (PVC), while styrene is polymerized to make polystyrene plastics.

In addition to industrial uses, ethylene plays a vital role in plant biology. It is a natural plant hormone that regulates various aspects of growth, development, and stress responses. Ethylene influences processes such as fruit ripening, flower wilting, leaf abscission, and germination. It is produced by plant tissues and acts as a signaling molecule, often in response to environmental stress or during specific stages of development.

Ethylene’s role in agriculture is applied in post-harvest management. Commercially, ethylene gas is used to trigger uniform ripening of fruits like bananas and tomatoes during storage and transportation. Conversely, ethylene inhibitors can be applied to delay ripening and prolong shelf life.

The handling of ethylene requires caution due to its flammability and potential for explosive mixtures with air. It is transported and stored under pressure as a liquefied gas in specialized containers. Proper ventilation and fire prevention measures are essential in facilities that use or produce ethylene.

Analytical techniques used to study ethylene include gas chromatography (GC) for quantitative analysis, and infrared (IR) spectroscopy to observe characteristic C=C stretching vibrations. Nuclear magnetic resonance (NMR) spectroscopy is also used to confirm the chemical structure and monitor polymerization reactions involving ethylene.

In summary, ethylene is a foundational compound in both industrial chemistry and plant biology. Discovered in the 18th century and extensively studied thereafter, it has become central to the production of plastics, solvents, and fibers, while also serving as a critical natural regulator in plant physiology. Its synthesis, applications, and biological roles are well-documented and continue to be of major importance across scientific and commercial domains.

References

2025. N-doped Cu2O with the tunable Cu0 and Cu+ sites for selective CO2 electrochemical reduction to ethylene. Journal of Environmental Sciences (China).
DOI: 10.1016/j.jes.2024.03.012

2025. Sustainable active packaging developed using starch-based foam incorporating 1-Methylcyclopropene@α-Cyclodextrin. Carbohydrate Polymers.
DOI: 10.1016/j.carbpol.2024.122696

2024. Methionine represses gray mold of tomato by keeping nitric oxide at an appropriate level via ethylene synthesis and signal transduction. Food Chemistry.
DOI: 10.1016/j.foodchem.2024.140942