Difference Between Ethylene and Propylene Glycol

Ethylene vs Propylene Glycol
 

Ethylene glycol and propylene glycol are organic compounds with alcohol functional groups. The term “glycol” is used when there are two hydroxyl groups present in neighboring carbon atoms.  Their molecular formulas are different; thus they have some different physical properties. However, when considered the uses, both are used for somewhat same purposes.

Ethylene Glycol

Ethylene glycol is an organic compound with two carbon atoms and two hydroxyl groups. Each hydroxyl group is separately attached to one carbon atom. The IUPAC name of ethylene glycol is Ethane-1,2-diol. It has the following structure.

Ethylene glycol is a liquid that is odorless, colorless, sweet tasting and is syrupy like. Its molar mass is 62.07 g mol⁻¹. Ethylene glycol has a melting point of 197.3 °C. It is miscible with water.

Ethylene glycol is produced from ethene. The intermediate is ethylene oxide and, when it is reacted with water, ethylene glycol is produced.

Ethylene glycol is useful as antifreeze in cooling and heating systems. It is also used as a solvent in paint and plastic industries. It is in the ink used by printers, and in stamp pad ink, Ballpoint pens etc. Further ethylene glycol is useful as industrial humectants, in hydraulic brake fluid, and as an ingredient of electrolytic condensers. Moreover, it is used in the synthesis of synthetic fibers, plasticizers, safety explosives, synthetic waxes etc.

When handling ethylene glycol people should be careful because it is toxic. Ingestion of large quantities of ethylene glycol can cause vomiting, coma, respiratory failure, convulsions, metabolic changes, cardiopulmonary effects etc.

Propylene Glycol

Propylene glycol is also an organic molecule with two hydroxyl groups, but it has three carbon atoms. The hydroxyl groups are attached to the first and the second carbon atoms. Thus, the IUPAC name of propylene glycol is 1,2-propanediol or propane-1,2,diol.  It has the following structure. It has a chiral carbon (3^rd carbon atom), therefore, propylene glycol exists in two stereoisomers. So when producing in the industry, a racemic mixture is resulting.

Propylene glycol is a viscous liquid without an odor or a color. It has a faint sweet taste. Propyelene glycol is miscible with water as well as with chloroform and acetone. Its molar mass is 76.09 g/mol.  Boiling point of propylene glycol is 188.2 °C.

Propylene glycol is produced from propylene oxide. This molecule has so many uses. It is used as a solvent in the pharmaceutical industry. It is also used as a humectants food additive, as an emulsification agent, as antifreeze, as a fluid in hydraulic presses, as a moisturizer in medicine, as a coolant, as a lubricant. It is also used to produce polyester compounds, in smoke machines, in hand sanitizers, in cosmetics, etc.