Cis-1,2-Ethanediol vs. Trans-1,2-Ethanediol

What's the Difference?

Cis-1,2-Ethanediol and Trans-1,2-Ethanediol are both isomers of the chemical compound 1,2-Ethanediol, also known as ethylene glycol. The main difference between the two isomers lies in the arrangement of the hydroxyl groups on the carbon atoms. In Cis-1,2-Ethanediol, the two hydroxyl groups are on the same side of the molecule, while in Trans-1,2-Ethanediol, they are on opposite sides. This difference in arrangement can lead to variations in the physical and chemical properties of the two isomers. For example, Cis-1,2-Ethanediol may have different melting and boiling points compared to Trans-1,2-Ethanediol, and may exhibit different reactivity in chemical reactions.


Chemical StructureCis-1,2-Ethanediol has two hydroxyl groups on the same side of the carbon chain.Trans-1,2-Ethanediol has two hydroxyl groups on opposite sides of the carbon chain.
Melting PointHigher melting point compared to Trans-1,2-Ethanediol.Lower melting point compared to Cis-1,2-Ethanediol.
Boiling PointHigher boiling point compared to Trans-1,2-Ethanediol.Lower boiling point compared to Cis-1,2-Ethanediol.

Further Detail


Cis-1,2-Ethanediol and Trans-1,2-Ethanediol are two isomers of the chemical compound 1,2-ethanediol, also known as ethylene glycol. These two isomers have similar chemical formulas but differ in their molecular structures, leading to distinct properties and behaviors. In this article, we will compare the attributes of Cis-1,2-Ethanediol and Trans-1,2-Ethanediol to understand their differences and similarities.

Chemical Structure

The main difference between Cis-1,2-Ethanediol and Trans-1,2-Ethanediol lies in their molecular structures. In Cis-1,2-Ethanediol, the two hydroxyl (-OH) groups are located on the same side of the carbon-carbon double bond, resulting in a bent molecular shape. On the other hand, in Trans-1,2-Ethanediol, the two hydroxyl groups are located on opposite sides of the double bond, leading to a linear molecular structure. This structural difference has significant implications for the physical and chemical properties of these isomers.

Physical Properties

One of the key differences in the physical properties of Cis-1,2-Ethanediol and Trans-1,2-Ethanediol is their melting points. Cis-1,2-Ethanediol has a lower melting point compared to Trans-1,2-Ethanediol. This difference can be attributed to the molecular arrangement in each isomer. The bent structure of Cis-1,2-Ethanediol allows for closer packing of molecules, leading to stronger intermolecular forces and a higher melting point. On the other hand, the linear structure of Trans-1,2-Ethanediol results in weaker intermolecular forces and a lower melting point.

Chemical Properties

When it comes to chemical properties, Cis-1,2-Ethanediol and Trans-1,2-Ethanediol exhibit differences in their reactivity. Due to their distinct molecular structures, these isomers react differently with other compounds. For example, Cis-1,2-Ethanediol may exhibit different solubility or reactivity in certain chemical reactions compared to Trans-1,2-Ethanediol. Understanding these differences is crucial for various applications in industries such as pharmaceuticals, polymers, and agriculture.


Both Cis-1,2-Ethanediol and Trans-1,2-Ethanediol have important applications in various industries. Cis-1,2-Ethanediol is commonly used as a solvent in chemical reactions and as a raw material in the production of polyester resins. Its unique properties make it suitable for applications where a bent molecular structure is desired. On the other hand, Trans-1,2-Ethanediol is used in antifreeze solutions, deicing agents, and as a coolant in automotive applications. Its linear structure allows for efficient heat transfer and anti-freezing properties.


Another important aspect to consider when comparing Cis-1,2-Ethanediol and Trans-1,2-Ethanediol is their toxicity. Both isomers are toxic to humans and animals if ingested, with symptoms ranging from gastrointestinal distress to organ failure. However, studies have shown that Trans-1,2-Ethanediol may have a lower toxicity compared to Cis-1,2-Ethanediol. This difference in toxicity levels can impact the handling and disposal of these chemicals in various industries.


In conclusion, Cis-1,2-Ethanediol and Trans-1,2-Ethanediol are two isomers of 1,2-ethanediol with distinct properties and applications. Their differences in molecular structure, physical and chemical properties, toxicity levels, and applications make them unique compounds with specific uses in various industries. Understanding the differences between these isomers is essential for utilizing them effectively and safely in different applications.

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