Main Difference – Ethylene Glycol vs Polyethylene Glycol
Although they have nearly similar names, polyethylene glycol and ethylene glycol are very different compounds depending on their chemical structures and general properties. Ethylene glycol is an alcoholic compound. Polyethylene glycol is a polyether compound. Both these compounds are miscible with water due to the presence of –OH groups. The main difference between ethylene glycol and polyethylene glycol is that ethylene glycol has a fixed value for molecular weight whereas polyethylene glycol has no fixed value for molecular weight.
Key Areas Covered
1. What is Ethylene Glycol
– Definition, Properties, Uses
2. What is Polyethylene Glycol
– Definition, Production, Uses
3. What is the Difference Between Ethylene Glycol and Polyethylene Glycol
– Comparison of Key Differences
Key Terms: Ethylene Glycol, Hydrogen Bonds, Polydispersity, Polyethylene Glycol, Polymerization
What is Ethylene Glycol
Ethylene glycol is a colorless and odorless alcoholic compound having the chemical formula C2H6O2. The molar mass of this compound is about 62.07 g/mol. At room temperature and pressure, ethylene glycol is a syrupy liquid. It is a viscous liquid. The boiling point of this liquid is about 198 °C.
Figure 1: Chemical Structure of Ethylene Glycol
Ethylene glycol is composed of two –OH groups in its structure. Therefore, this molecule is capable of forming hydrogen bonds with water molecules. Hence, ethylene glycol is miscible with water. The two –OH groups are attached to the adjacent carbon atoms.
Ethylene glycol is a sweet tasting syrupy liquid. The most common applications of ethylene glycol include its use as a raw material for the production of polyester fibers and as an automotive antifreeze. An automotive antifreeze is a liquid used in the radiator and cooling system of an internal combustion engine for vehicles. However, it is a moderately toxic compound.
What is Polyethylene Glycol
Polyethylene glycol is a polyether compound. The general formula of this compound is given as H−(O−CH2−CH2)n−OH. The molecular weight of the compound varies depending on the value of “n” in this general formula.
Figure 2: Molecular Formula of Polyethylene Glycol
The production of polyethylene glycol can be done form the reaction between ethylene oxide and water, ethylene glycol or ethylene glycol oligomers. This reaction needs an acidic or basic catalyst. When water is used for the reaction with ethylene oxide, the final product has a high polydispersity (the product has a high molecular weight distribution). Therefore the final product gives a variety of polymer compounds with different molecular weights. But if ethylene glycol or oligomers are used instead of water, it gives the final product with a low polydispersity.
The type of polymerization depends on the type of catalyst. It can be either cationic polymerization or anionic polymerization. However, anionic polymerization gives a low polydispersity. Therefore, it is more preferable. In addition, suspension polymerization can also be used.
Polyethylene glycol has many uses including medical uses, chemical uses, biological uses, industrial uses, etc. For example, it is used as an excipient in many pharmaceutical products.
Difference Between Ethylene Glycol and Polyethylene Glycol
Definition
Ethylene Glycol: Ethylene glycol is a colorless and odorless alcoholic compound having the chemical formula C2H6O2.
Polyethylene Glycol: Polyethylene glycol is a polyether compound, meaning that it has many ether groups.
General Formula
Ethylene Glycol: The general formula for ethylene glycol is C2H6O2.
Polyethylene Glycol: The general formula for polyethylene glycol is H−(O−CH2−CH2)n−OH.
Production
Ethylene Glycol: Ethylene glycol is produced from the reaction between ethylene oxide and water.
Polyethylene Glycol: Polyethylene glycol is produced from the reaction between ethylene oxide and water, ethylene glycol or ethylene glycol oligomers.
Molecular Weight
Ethylene Glycol: The molecular weight of ethylene glycol is about 62.07 g/mol.
Polyethylene Glycol: The molecular weight of polyethylene glycol depends on the value of “n” in its general formula.
Uses
Ethylene Glycol: Ethylene glycol is mainly used for the manufacturing of polyester fibers and as an automotive antifreeze.
Polyethylene Glycol: Polyethylene glycol has many uses including medical uses, chemical uses, biological uses, industrial uses, etc.
Conclusion
Both Ethylene glycol and Polyethylene glycol are commercially very important and used in a number of applications. Ethylene glycol is a syrupy liquid at room temperature whereas polyethylene glycol is a solid material. The main difference between ethylene glycol and polyethylene glycol is that ethylene glycol has a fixed value for molecular weight whereas polyethylene glycol has no fixed value for molecular weight.
References:
1. Wade, Leroy G. “Ethylene glycol.” Encyclopædia Britannica, Encyclopædia Britannica, inc., 2 Dec. 2011, Available here.
2. “ETHYLENE GLYCOL.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine, Available here.
Image Courtesy:
1. “Ethylene glycol” By Sander de Jong – Own work (Public Domain) via Commons Wikimedia
2. “Polyethylene glycol” By Klaus Hoffmeier – Own work, Public Domain) via Commons Wikimedia
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