Chem Explorers

The Polar and Versatile Compound: Ethylene Glycol

Ethylene Glycol: Molecular Structure and Polarity

1. Chemical Formula and IUPAC Name

Ethylene glycol, also known as monoethylene glycol, is a colorless, odorless, and sweet-tasting liquid with various uses, from automotive coolants and antifreeze to personal care products and food flavorings. Its chemical formula is C2H6O2, meaning it consists of two carbon (C) atoms, six hydrogen (H) atoms, and two oxygen (O) atoms. Using the IUPAC nomenclature, we can also refer to ethylene glycol as ethane-1,2-diol since it contains two hydroxyl (-OH) groups attached to adjacent carbon atoms.

2. Polarity and Molecular Structure

2.1. Dipole Moment and Electronegativity

To understand whether ethylene glycol is polar or non-polar, we need to examine its net dipole moment, which indicates the overall charge distribution within the molecule. This dipole moment arises from the difference in electronegativity between bonded atoms, measuring their ability to attract shared electrons. In ethylene glycol, the C-C and C-H bonds are non-polar due to the small electronegativity difference between carbon and hydrogen atoms. However, the C-O and O-H bonds are polar since oxygen is more electronegative than carbon and hydrogen. As a result, the electrons in these bonds are pulled closer to oxygen, creating partially negative (-) and partially positive (+) charges on the respective atoms.

2.2. Molecular Geometry

The molecular geometry of ethylene glycol significantly influences its polarity. According to the valence shell electron pair repulsion (VSEPR) theory, the molecule adopts a tetrahedral geometry with a bond angle of approximately 109.5 degrees. The two -OH groups occupy two of the four corners of the tetrahedron, while the other two are occupied by the carbon atom and one hydrogen atom. Due to the bent shape of the -OH groups, the net dipole moment does not cancel out, making the molecule polar.

2.3. Polar vs. Non-Polar Molecules

In general, polar molecules have a net dipole moment due to unequal electron sharing between bonded atoms, resulting in a permanent separation of charges. Non-polar molecules, such as methane (CH4), have an even charge distribution because their bonds are symmetrical, and the electronegativity difference is negligible. Examples of polar molecules include water (H2O), ammonia (NH3), and hydrogen chloride (HCl), while examples of non-polar molecules include oxygen (O2), nitrogen (N2), and carbon dioxide (CO2).

3. FAQs

3.1. Formal Charge of Atoms

The formal charge is a method to assign charges to each atom in a molecule or ion based on its valence electrons. To calculate the formal charge of an atom, subtract half the number of shared electrons and all the lone electrons from the number of valence electrons it would have in a free state. In ethylene glycol, the formal charge of carbon is 0 (4 – 2 – 2), hydrogen is 0 (1 – 0 – 1), and oxygen is -1 (6 – 4 – 2) for each -OH group.

3.2. Water Solubility

Ethylene glycol’s water solubility arises from its polarity, allowing it to interact with water’s polar properties through hydrogen bonding. This interaction leads to strong intermolecular attractions, making it soluble in water.

3.3. Polarity Comparison with Other Compounds

Ethylene glycol is more polar than ethanol (C2H5OH) due to its two -OH groups compared to ethanol’s single -OH group. This increases the charge separation and overall dipole moment. However, it is less polar than glycerol (C3H8O3) because glycerol contains three -OH groups, further increasing the net dipole moment.

4. Physical Properties

Ethylene glycol has a molar mass of 62.07 g/mol and is a colorless, odorless, and sweet-smelling liquid. Its high viscosity, meaning it flows slowly and resists deformation, makes it useful in lubricating oils and hydraulic fluids. The boiling point of ethylene glycol is 197 degrees Celsius, while its melting point is -13 degrees Celsius, making it a useful antifreeze component for automobiles. Mixing it with water prevents engine damage in cold temperatures.

5. Applications

5.1. Antifreeze

One of the primary uses of ethylene glycol is as an antifreeze agent in automobile engines. Its mixture with water, with ethylene glycol as the main component, lowers the freezing point of water, preventing ice formation, and raises the boiling point, preventing engine overheating. However, it is crucial to remember that ethylene glycol is toxic to humans and animals if ingested. Its sweet taste can lead to accidental ingestion, causing severe poisoning and death. Therefore, handling and disposing of ethylene glycol should be done with utmost care.

5.2. Water Solubility

Ethylene glycol’s high water solubility makes it useful in various applications, including the manufacturing of personal care products and food flavorings. Its polarity allows it to act as a solvent, interacting with water through hydrogen bonding.

6. Sources and References

When researching ethylene glycol, it’s essential to rely on credible sources to ensure accuracy and reliability. Britannica and Toppr are trusted sources of information for general chemistry knowledge, providing in-depth explanations on ethylene glycol’s properties and applications. Wikipedia, while a useful starting point, should be used cautiously as anyone can contribute to its articles. Verify information with other sources. The Molecule of the Month article series by the University of Bristol’s Chemistry department offers detailed information on various molecules, including ethylene glycol, in an accessible and informative style.

7. Conclusion

Ethylene glycol is a versatile chemical compound with numerous applications due to its unique physical and chemical properties. However, it should be handled and disposed of with care to avoid environmental impacts and health hazards. When researching ethylene glycol, it is crucial to rely on reputable sources to ensure accuracy and reliability. In summary, ethylene glycol is a polar chemical compound with numerous applications across various industries. Its physical and chemical properties are crucial in antifreeze formulations, personal care products, and food flavorings. However, its toxicity to humans and animals and potential environmental damage upon improper disposal require cautious handling and disposal practices to avoid health and environmental hazards.


1. What is ethylene glycol, and what is it used for?

Ethylene glycol is a chemical compound with various applications, including antifreeze, personal care and food products, and as a solvent.

2. Why is ethylene glycol toxic to humans and animals?

Ethylene glycol is toxic because it breaks down into toxic chemicals in the body, leading to kidney and liver damage and even death. Its sweet taste can also lead to accidental ingestion.

3. Is ethylene glycol water-soluble?

Yes, it is highly water-soluble due to its polarity, which allows it to interact with water through hydrogen bonding.

4. How can ethylene glycol be handled and disposed of safely?

Ethylene glycol should be handled with care, and its disposal should conform to environmental regulations. Recycling or using approved waste disposal methods is recommended.

5. What are some trustworthy sources for research on ethylene glycol?

Britannica and Toppr are reputable sources of information for general chemistry knowledge, while the Molecule of the Month article series by the University of Bristol’s Chemistry department provides detailed data on molecules like ethylene glycol.

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