Propylene glycol

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Propylene glycol
IUPAC name
Other names
α-Propylene glycol
Methyl ethyl glycol (MEG)
Methylethylene glycol
Molar mass 76.10 g/mol
Appearance Colorless liquid
Odor Odorless
Density 1.036 g/cm3
Melting point −59 °C (−74 °F; 214 K)
Boiling point 188.2 °C (370.8 °F; 461.3 K)
Solubility Miscible with acetone, chloroform, diethyl ether, ethanol, methanol
Vapor pressure 0.05 mmHg at 20 °C
Acidity (pKa) 14.8
Safety data sheet Sigma-Aldrich
Flash point 103 °C (217.4 °F; 376 K)
Related compounds
Related compounds
Ethylene glycol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Propylene glycol, also called propane-1,2-diol or α-propylene glycol to differentiate it from its propane-1,3-diol isomer, is an organic compound with the chemical formula C3H8O2.



Propylene glycol is metabolized in the human body to pyruvic acid.

Acid catalyzed dehydration of propylene glycol will give dimethyl dioxane.


Propylene glycol is a colorless viscous liquid, with a slight sweet taste and almost odorless. It is miscible with many solvents, such as water, methanol, ethanol, isopropanol, diethyl ether, acetone, chloroform. It melts at −59 °C and boils at 188.2 °C. Propylene glycol does not form azeotrope with water, meaning that it can be simply distilled from an aqueous mixture easily.


Propylene glycol is available as antifreeze, but one must read the label very carefully, as most antifreeze products contain ethylene glycol. Due to its low toxicity, propylene glycol can be purchased from certain food stores and chemical suppliers, in various grades.

Rum essence and vanilla extracts is a mixture of propylene glycol, water preservatives and flavors. The glycol can be extracted via drying and purification. Due to PG's high boiling point, vacuum distillation is recommended.


Propylene glycol can be prepared by the hydrolysis of propylene oxide. However as propylene glycol is more available, it's much more cheaper to just buy it.




Propylene glycol has a very low toxicity and has even been approved to be used in food products. It may cause irritations to some people however.

The biggest danger is the occasional confusion with ethylene glycol which is much more toxic (quite deadly) that its propylene counterpart, as both are sometimes called "glycol" for short, so it's best to read the label.


Propylene glycol should be stored in closed bottles, away from any fire source.


Propylene glycol is nontoxic for the environment and can be safely burned.


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