Propylene oxide

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Propylene oxide
Structural formula
Ball-and-stick model of the propylene oxide molecule
Preferred IUPAC name
Other names
Propylene oxide
Propylene epoxide
1,2-Propylene oxide
Methyl oxirane
Propene oxide
Methyl ethylene oxide
Methylethylene oxide
3D model (JSmol)
ECHA InfoCard 100.000.800
EC Number 200-879-2
Molar mass 58.08 g·mol−1
Appearance Colorless liquid
Odor benzene-like[1]
Density 0.859 g/cm3[2]
Melting point −111.9 °C (−169.4 °F; 161.2 K)[2]
Boiling point 35 °C (95 °F; 308 K)[2]
41% (20°C)[1]
Vapor pressure 445 mmHg (20°C)[1]
-42.5·10−6 cm3/mol[3]
120.4 J·(K·mol)−1
196.5 J·(K·mol)−1
−123.0 kJ·mol−1[4]
Main hazards Extremely flammable[5][6]
GHS pictograms The flame pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)The health hazard pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)The exclamation-mark pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal word DANGER!
NFPA 704
Flammability code 4: Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23 °C (73 °F). E.g., propaneHealth code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gasReactivity code 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g., phosphorusSpecial hazards (white): no codeNFPA 704 four-colored diamond
Flash point −37 °C (−35 °F; 236 K)
747 °C (1,377 °F; 1,020 K)
Explosive limits 2.3–36%[1]
Lethal dose or concentration (LD, LC):
660 mg/kg (guinea pig, oral)
380 mg/kg (rat, oral)
440 mg/kg (mouse, oral)
1140 mg/kg (rat, oral)
690 mg/kg (guinea pig, oral)[7]
1740 ppm (mouse, 4 h)
4000 ppm (rat, 4 h)[7]
2005 ppm (dog, 4 h)
4000 ppm (guinea pig, 4 h)[7]
US health exposure limits (NIOSH):
PEL (Permissible)
TWA 100 ppm (240 mg/m3)[1]
REL (Recommended)
IDLH (Immediate danger)
Ca [400 ppm][1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is ☑Y☒N ?)
Infobox references

Propylene oxide is an organic compound with the molecular formula CH3CHCH2O. This colourless volatile liquid with an odour resembling ether, is produced on a large scale industrially. Its major application is its use for the production of polyether polyols for use in making polyurethane plastics. It is a chiral epoxide, although it is commonly used as a racemic mixture.

This compound is sometimes called 1,2-propylene oxide to distinguish it from its isomer 1,3-propylene oxide, better known as oxetane.


Industrial production of propylene oxide starts from propylene. Two general approaches are employed, one involving hydrochlorination and the other involving oxidation.[8] In 2005, about half of the world production was through chlorohydrin technology and one half via oxidation routes. The latter approach is growing in importance.[9]

Hydrochlorination route[edit]

The traditional route proceeds via the conversion of propylene to propylene chlorohydrin, which is produced according to the following simplified scheme:

Propylenoxid Darstellung 1.svg

The mixture of 1-chloro-2-propanol and 2-chloro-1-propanol, which is then dehydrochlorinated. For example:

Propylenoxid Darstellung 2.svg

Lime (Ca(OH)2) is often used to absorb the HCl.

Oxidation of propylene[edit]

The other general route to propylene oxide involves oxidation of propylene with an organic peroxide. The reaction follows this stoichiometry:


The process is practiced with three hydroperoxides:[9]

In March 2009, BASF and Dow Chemical started up their new HPPO plant in Antwerp.[11] In the HPPO-Process, propylene is oxidized with hydrogen peroxide:

In this process no side products other than water are generated.[12]


Reactions of propylene oxide include:[13]


Between 60 and 70% of all propylene oxide is converted to polyether polyols by the process called alkoxylation.[14] These polyols are building blocks in the production of polyurethane plastics.[15] About 20% of propylene oxide is hydrolyzed into propylene glycol, via a process which is accelerated by acid or base catalysis. Other major products are polypropylene glycol, propylene glycol ethers, and propylene carbonate.

Historic and niche uses[edit]

Propylene oxide was once used as a racing fuel, but that usage is now prohibited under the US NHRA rules for safety reasons. It has also been used in glow fuel for model aircraft and surface vehicles, typically combined in small percentages of around 2% as an additive to the typical methanol, nitromethane, and oil mix. It is also used in thermobaric weapons, and microbial fumigation.


The United States Food and Drug Administration has approved the use of propylene oxide to pasteurize raw almonds beginning on September 1, 2007, in response to two incidents of contamination by Salmonella in commercial orchards, one incident occurring in Canada and one in the United States.[16][17] Pistachio nuts can also be subjected to propylene oxide to control Salmonella.


Propylene oxide is commonly used in the preparation of biological samples for electron microscopy, to remove residual ethanol previously used for dehydration. In a typical procedure, the sample is first immersed in a mixture of equal volumes of ethanol and propylene oxide for 5 minutes, and then four times in pure oxide, 10 minutes each.


It is a probable human carcinogen, and is included into the List of IARC Group 2B carcinogens.[18]

Natural occurrence[edit]

In 2016 it was reported that propylene oxide was detected in Sagittarius B2, a cloud of gas in the Milky Way weighing three million solar masses. It is the first chiral molecule to be detected in space.[19]


  1. ^ a b c d e f g "NIOSH Pocket Guide to Chemical Hazards #0538". National Institute for Occupational Safety and Health (NIOSH). 
  2. ^ a b c d Haynes, p. 3.384
  3. ^ Haynes, p. 3.577
  4. ^ Haynes, p. 5.24
  5. ^ "NFPA DIAMOND".
  6. ^ GOV, NOAA Office of Response and Restoration, US. "PROPYLENE OXIDE | CAMEO Chemicals | NOAA".
  7. ^ a b c "Propylene oxide". Immediately Dangerous to Life and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH). 
  8. ^ Kahlich, Dietmar; Wiechern, Uwe and Lindner, Jörg (2002) "Propylene Oxide" in Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH, Weinheim. doi:10.1002/14356007.a22_239
  9. ^ a b Nijhuis, T. Alexander; Makkee, Michiel; Moulijn, Jacob A.; Weckhuysen, Bert M (2006). "The Production of Propene Oxide: Catalytic Processes and Recent Developments". Industrial & Engineering Chemistry Research. 45 (10): 3447. doi:10.1021/ie0513090. 
  10. ^ "Summary of Sumitomo process from Nexant Reports". Archived from the original on 2006-01-17. Retrieved 2007-09-18. 
  11. ^ "New BASF and Dow HPPO Plant in Antwerp Completes Start-Up Phase". Archived from the original on 2012-07-21. Retrieved 2009-03-05. 
  12. ^ Tullo, Alex (2004). "Dow, BASF to build Propylene Oxide". Chemical & Engineering News Archive. 82 (36): 15. doi:10.1021/cen-v082n036.p015a. 
  13. ^ Heilbron, Ian, ed. (1953). Dictionary of Organic Compounds. 4. p. 249. 
  14. ^ Adam, Norbert et al. (2005) "Polyurethanes" in Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH, Weinheim. doi:10.1002/14356007.a21_665.pub2
  15. ^ "Usage of proplyene oxide, from Dow Chemical". Retrieved 2007-09-10. 
  16. ^ Guidance for Industry: Measures to Address the Risk for Contamination by Salmonella Species in Food Containing a Pistachio-Derived Product As An Ingredient; Draft Guidance. U.S. FDA (June 2009)
  17. ^ Agricultural Marketing Service, USDA (30 March 2007). "Almonds Grown in California; Outgoing Quality Control Requirements" (PDF). Federal Register. 72 (61): 15,021–15,036. Archived from the original (PDF) on 28 September 2007. Retrieved 2007-08-22. 
  18. ^ Grana, R; Benowitz, N; Glantz, SA (13 May 2014). "E-cigarettes: a scientific review". Circulation. 129 (19): 1972–86. doi:10.1161/circulationaha.114.007667. PMC 4018182Freely accessible. PMID 24821826. 
  19. ^ "Scientists just detected this life-forming molecule in interstellar space for the first time". Science Alert. 2016-06-15. 

Cited sources[edit]

External links[edit]