Ethylene glycol
[CAS# 107-21-1]

Identification

• Classification: Organic raw materials >> Alcohols, phenols, phenolic compounds and derivatives >> Acyclic alcohol
• Name: Ethylene glycol
• Synonyms: 1,2-Ethanediol; Monoethylene glycol
• Molecular Formula: C₂H₆O₂
• Molecular Weight: 62.07
• CAS Registry Number: 107-21-1
• EC Number: 203-473-3
• SMILES: C(CO)O

Properties

• Density: 1.113 g/mL
• Melting point: -13 °C
• Boiling point: 196-198 °C
• Refractive index: 1.43-1.433
• Flash point: 116 °C
• Water solubility: miscible

Safety Data

• Hazard Symbols: GHS07;GHS08 Warning
• Risk Statements: H302-H373
• Safety Statements: P260-P264-P270-P301+P317-P319-P330-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute toxicity	Acute Tox.	4	H302
Specific target organ toxicity - repeated exposure	STOT RE	2	H373
Specific target organ toxicity - repeated exposure	STOT RE	1	H372
Eye irritation	Eye Irrit.	2	H319
Specific target organ toxicity - single exposure	STOT SE	1	H370
Specific target organ toxicity - single exposure	STOT SE	3	H336
Skin irritation	Skin Irrit.	2	H315
Reproductive toxicity	Repr.	1B	H360
Chronic hazardous to the aquatic environment	Aquatic Chronic	3	H412
Germ cell mutagenicity	Muta.	1B	H340

Discovery and Applications

Ethylene glycol is an organic compound with the molecular formula C₂H₆O₂, and the structural formula HOCH₂CH₂OH. It is the simplest member of the glycol family, consisting of two hydroxyl groups attached to a two-carbon alkyl chain. In its pure form, ethylene glycol is a colorless, odorless, sweet-tasting, viscous liquid that is miscible with water and many polar organic solvents.

The compound was first prepared in the mid-19th century by the French chemist Charles-Adolphe Wurtz via the hydration of ethylene oxide. Since then, the production process has evolved significantly, and today ethylene glycol is primarily manufactured through the catalyzed hydration of ethylene oxide. This method is widely used in industry due to its efficiency and high product yield.

Ethylene glycol is best known for its use as an antifreeze agent in automotive and industrial cooling systems. When mixed with water, it lowers the freezing point and raises the boiling point of the solution, providing protection against extreme temperatures. This property makes it essential for use in internal combustion engine cooling systems in a wide range of climates.

Another major application of ethylene glycol is in the production of polyethylene terephthalate (PET), a common plastic used to manufacture beverage bottles, food packaging, and synthetic fibers. In this application, ethylene glycol acts as a monomer in the polymerization process, reacting with terephthalic acid or its dimethyl ester to form PET. The demand for PET has made ethylene glycol a critical feedstock in the global plastics industry.

In addition to its roles in antifreeze formulations and PET production, ethylene glycol serves as an intermediate in the manufacture of other chemicals, including unsaturated polyester resins and plasticizers. It is also used as a solvent in various industrial applications and as a dehydrating agent in natural gas processing to remove water vapor.

Ethylene glycol is toxic to humans and animals when ingested. Its metabolism in the body leads to the formation of oxalic acid and other harmful compounds that can cause metabolic acidosis, kidney failure, and central nervous system depression. Due to its sweet taste, accidental or intentional ingestion is a known risk, especially for children and pets. As a result, efforts have been made to reduce such risks by adding bittering agents to commercial antifreeze products to deter ingestion.

In controlled laboratory settings, ethylene glycol is used in the synthesis of organics, particularly in reactions that require diols or the formation of cyclic acetals and ketals. It is also employed as a cryoprotectant in biological and biochemical research, where it helps protect cells and tissues during freezing.

Ethylene glycol has a boiling point of approximately 197 °C and a melting point of about –12.9 °C. It is stable under normal storage conditions but may form explosive peroxides upon prolonged exposure to air and light. Appropriate safety precautions are necessary when handling the substance, especially in high-temperature environments or in confined spaces.

The compound remains a vital part of the global chemical industry, with well-established applications in automotive, textile, packaging, and research sectors. Its continued use is supported by extensive literature confirming its chemical behavior, industrial relevance, and health and safety considerations.

References

1976. Reaction of hydrogen bromide with diols of long chain α,β-unsaturated acids. Journal of the American Oil Chemists' Society, 53(4).
DOI: 10.1007/bf02586346

2021. Methanolic extract of Cucumis melo attenuates ethylene glycol-induced nephrolithiasis in Wistar rats. Urolithiasis, 49(5).
DOI: 10.1007/s00240-021-01263-5

2021. Analysis of the polyester clothing value chain to identify key intervention points for sustainability. Environmental Sciences Europe, 33(1).
DOI: 10.1186/s12302-020-00447-x