Ethylene oxide

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Ethylene oxide
IUPAC name
Other names
1,2-Epoxy ethane
Dimethylene oxide
Molar mass 44.05 g/mol
Appearance Colorless gas
Odor Sweet, ether-like
Density 0.882 g/cm3 (at 10 °C)
Melting point −111.3 °C (−168.3 °F; 161.8 K)
Boiling point 10.7 °C (51.3 °F; 283.8 K)
Solubility Miscible with carbon tetrachloride, ethers
Soluble in acetone, benzene, diethyl ether, ethanol
Vapor pressure 1.46 atm (20°C)
243 J·mol−1·K−1
−52.6 kJ·mol−1
Safety data sheet Praxair
Flash point −20 °C
Lethal dose or concentration (LD, LC):
836 ppm (mouse, 4 hr)
4000 ppm (rat, 4 hr)
800 ppm (rat, 4 hr)
819 ppm (guinea pig, 4 hr)
1460 ppm (rat, 4 hr)
835 ppm (mouse, 4 hr)
960 ppm (dog, 4 hr)
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

Ethylene oxide, properly called oxirane by IUPAC, is the organic compound with the formula C2H4O. It is the simplest epoxide and cyclic ether. Ethylene oxide is isomeric with acetaldehyde and vinyl alcohol.



Ethylene oxide is highly flammable and will burn in open air.

C2H4O + 5/2 O2 → 2 CO2 + 2 H2O


Ethylene oxide is a colorless gas at room temperature, but liquid below 10°C, with a sweet ether-like smell (some sources say bruised-apple like[1]). It is miscible with water, carbon tetrachloride and other organic solvents.


Ethylene oxide is sold by various chemical suppliers, either pure or in solution, but due to its strong carcinogenicity it's sale is restricted to companies.


The preparation of ethylene oxide is not easy, but can be done if the procedure is followed carefully.

Industrially EO is made through direct oxidation of ethylene with oxygen in the presence of a metal catalyst, such as silver.

A more convenient process involves the reaction of 2-chloroethanol with a base, such as calcium hydroxide.

2 OH–CH2CH2–Cl + Ca(OH)2 → 2 (CH2CH2)O + CaCl2 + 2 H2O

The resulting ethylene oxide is purified through rectification and condensed.

Another route is to absorb dry hydrogen chloride gas into warm ethylene glycol, in the presence of anhydrous zinc chloride and distill the resulting 2-chloroethanol. Some water will also distill and must be removed. Plenty of 1,2-dichloroethane will be produced as a side product.

1,2-Diiodoethane will react with silver oxide to yield ethylene oxide at high temperatures.

A less known route involves refluxing dichloroethane at 105 °C in the presence of potassium hydroxide and sodium formate.[2]


Ethylene glycol is a very useful reagent, but its use is limited due to its toxicity. Wear proper protection when working with the compound.

  • Make polyethylene glycol
  • Make very pure ethylene glycol
  • Preparation of ethanolamines
  • Phenethyl alcohol synthesis
  • Make ethylene carbonate



Ethylene oxide is extremely flammable, very toxic and a potent carcinogen. It's sweet smell can induce the false sense of safety.


Ethylene oxide should be stored in gas cylinders, in dark well ventilated areas.


Ethylene oxide can be safely burned outside. Hydrolysis will lead to ethylene glycol which is non-volatile and safer to handle.


  1. Reynolds, J.E.F., Prasad, A.B. (eds.) Martindale-The Extra Pharmacopoeia. 28th ed. London: The Pharmaceutical Press, 1982., p. 562
  2. Zahalka, Hayder A.; Sasson, Yoel; Synthesis; nb. 9; (1986); p. 763 - 765

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