Propylene Oxide Home


Propylene oxide is a colorless, low-boiling, highly volatile liquid with a sweet, ether-like odor. It is flammable and reactive, so storage and unloading areas must be specifically designed and monitored. Dow offers technical and product stewardship support by way of periodic safe handling and storage reviews, and training.

Use the table below to locate property information for propylene oxide.

Chemical Name 1,2 epoxypropane
Synonyms 2-methyloxirane
1,2-propylene oxide
methyl ethylene oxide
Formula C3H6O
Molecular Weight (g/mol) 58.08
CAS Number 000075-56-9
EINECS Number 200-879-2
Density 25°C (77°F) 0.821 g/cm3 (6.861 lb./gal)
Vapor Density (Air = 1.0) 2.0
Vapor Pressure, 25°C (77°F) 71.7 kPa (538 mm Hg)
Freezing Point -111.93°C (-169.47°F)
Boiling Point, 101.3 kPa 34.2°C (93.56°F)
Specific Gravity, 25/25°C (77°F) 0.8253
Refractive Index n20/D°C (68°F) 1.36610
n25/D°C (77°F) 1.36335
Viscosity, 25°C (77°F) 0.305 centipoise
Specific Heat, 0°C (32°F) 2.08 J/(g°K) (0.5 Btu/lb/°F)
Auto-Ignition Temperature, in Air, 101.3 kPa 449°C (840.2°F)
Explosive limits in air, 25°C, 101.3 kPa 2.3 – 37.0 vol %
Flash Point, TAG-Closed cup -37.2°C (-35°F)
Heat of Combustion, 25°C, 101.3 kPa -33035 kJ/kg
Heat of Vaporization, 101.3 kPa 465.7 kJ/kg
Solubility in water, at 20°C (68°F) 40.5 wt %
Solubility of water in propylene oxide at 20°C 14.7 wt %

For Propylene Oxide Safety Data Sheets, Technical Data Sheets and other technical documents, please go to Technical Information.