Key Difference – Ethylene Glycol vs Polyethylene Glycol
Ethylene glycol and polyethylene glycol are two important members of the glycol family. The key difference between ethylene glycol and polyethylene glycol is their chemical structure. Ethylene glycol is a simple linear molecule, whereas polyethylene glycol is a polymeric material. In addition, both of these compounds are commercially very important and used in a number of applications.
What is Ethylene Glycol?
The IUPAC name of ethylene glycol is ethane-1,2-diol, and its molecular formula is (CH2OH)2. It is an organic compound which can be used as a raw material to manufacture polyester fibers and antifreeze formulations. It is an odorless, colorless, sweet-tasting viscous dihydroxy alcohol. Ethylene glycol is moderately toxic if ingested. It is the most commonly available glycol and is commercially produced in large quantities. It has many industrial applications; it is used as an antifreeze coolant in hydraulic fluids and in the manufacturing of low-freezing dynamites and resins.
What is Polythene Glycol?
Polyethylene glycol (PEG) is a polymeric compound, and it is used in a wide range of areas such as chemical, biological, medical, industrial and commercial applications. It is also known as polyethylene oxide (PEO) or polyoxyethylene (POE), depending on its molecular weight. Its’ structure is commonly written as H−(O−CH2−CH2)n−OH. PEG is a clear liquid or a water-soluble white solid with a mild odor.
What is the difference between Ethylene Glycol and Polythene Glycol?
Ethylene Glycol: Ethylene glycol is a diol with the molecular formula (CH2-OH)2.
Polythene Glycol: The molecular formula of PEG is (C2H4O)n+1H2O and its structural formula is expressed as below.
Ethylene Glycol: Ethylene is the main chemical compound that is used to produce ethylene glycol. During this process, ethylene oxide is produced as an intermediate, and it then reacts with water to produce ethylene glycol.
C2H4O + H2O → HO–CH2CH2–OH
Both acids and bases can be used as catalysts for this reaction. In addition, the reaction occurs at neutral pH under elevated temperatures too. A high yield (90%) can be obtained when the reaction occurs at acidic or neutral pH, in the presence of excess amount of water.
Polythene Glycol: The reaction between ethylene oxide with water, ethylene glycol or ethylene glycol oligomers produces polyethylene glycol. Both acidic and basic catalysts are used to catalyze this reaction. The reaction between ethylene glycol and its oligomers is preferable than with water. The length of the polymer chain depends on the ratio of reactants. The polymerization mechanism can be cationic or anionic polymerization depending on the type of catalyst.
HOCH2CH2OH + n(CH2CH2O) → HO(CH2CH2O)n+1H
Ethylene Glycol: Ethylene glycol is mainly used in antifreeze formulations and as a raw material in the manufacturing of polyesters such as polyethylene terephthalate (PET) in plastic industry. Ethylene glycol can facilitate convective heat transfer in automobiles and liquid cooled computers. It is also used in chilled water air conditioning systems.
Polythene Glycol: Polythene glycol possesses a low toxicity and therefore it is used as a lubricating coating for both aqueous and non-aqueous environments. It is also used as a polar stationary phase in gas chromatography and as a heat transfer fluid in electronic testers. PEG is the base for many skin creams and personal lubricants. It is used in a number of toothpaste as a dispersant and as an anti-foaming agent in food industrial applications.References: “ETHYLENE GLYCOL” - Open Chemistry Database “Ethylene glycol” - Wikipedia “Polyethylene glycol” – Wikipedia “POLYETHYLENE GLYCOL” – University of Teknologi MARA Image Courtesy: “Ethylene glycol chemical structure” (CC BY-SA 3.0) via Commons Wikimedia “Polyethylene glycol” By Klaus Hoffmeier – Own work (Public Domain) via Commons Wikimedia