Editing Propylene oxide

{{chembox
|Verifiedfields = changed
|Watchedfields = changed
|verifiedrevid = 413113516
|ImageFile = Propylene oxide.svg
|ImageSize = 165
|ImageName = Structural formula
|ImageFile1 = (S)-Propylene oxide molecule ball.png
|ImageSize1 = 165
|ImageName1 = Ball-and-stick model of the propylene oxide molecule
|PIN = (2R)-2-Methyloxirane<br>(2S)-2-Methyloxirane
|OtherNames = Propylene oxide<br />Epoxypropane<br />Propylene epoxide<br />1,2-Propylene oxide<br />Methyl oxirane<br />1,2-Epoxypropane<br />Propene oxide<br />Methyl ethylene oxide<br />Methylethylene oxide
|Section1={{Chembox Identifiers
|CASNo = 75-56-9
|CASNo_Ref = {{cascite|correct|CAS}}
|UNII_Ref = {{fdacite|correct|FDA}}
|UNII = Y4Y7NYD4BK
|EINECS = 200-879-2
|SMILES = CC1CO1
|PubChem = 6378
|ChemSpiderID = 6138
|StdInChI = 1S/C3H6O/c1-3-2-4-3/h3H,2H2,1H3
|StdInChIKey = GOOHAUXETOMSMM-UHFFFAOYSA-N
|ChEBI_Ref = {{ebicite|changed|EBI}}
|ChEBI = 38685
|KEGG_Ref = {{keggcite|changed|kegg}}
|KEGG = C15508
}}
|Section2={{Chembox Properties
|C=3 | H=6 | O=1
|Appearance = Colourless liquid
|Odor = benzene-like<ref name=PGCH/>
|Density = 0.859 g/cm<sup>3</sup><ref name=b92/>
|MeltingPtC = −111.9
|MeltingPt_ref =<ref name=b92/>
|BoilingPtC = 35
|BoilingPt_ref = <ref name=b92>{{harvnb | Haynes | 2011 | p=3.384}}</ref>
|Solubility = 41% (20&nbsp;°C)<ref name=PGCH/>
|VaporPressure = 445 mmHg (20&nbsp;°C)<ref name=PGCH/>
|RefractIndex = 1.3660<ref name=b92/>
|MagSus = {{val|-4.25e-5|u=cm<sup>3</sup>/mol}}<ref>{{harvnb | Haynes | 2011 | p=3.577}}</ref>
}}
|Section3={{Chembox Thermochemistry
|DeltaHf = −123.0{{nbsp}}kJ·mol<sup>−1</sup><ref name=b92b>{{harvnb | Haynes | 2011 | p=5.24}}</ref>
|Entropy = 196.5{{nbsp}}J·(K·mol)<sup>−1</sup>
|HeatCapacity = 120.4{{nbsp}}J·(K·mol)<sup>−1</sup>
}}
|Section4={{Chembox Hazards
|GHSPictograms = {{GHS02}}{{GHS08}}{{GHS07}}
|GHSSignalWord = DANGER
|MainHazards = Extremely flammable<ref>[http://www.otrain.com/OTI_MSDS(NFPA)PMAP.html "NFPA DIAMOND"]. ''www.otrain.com''.</ref><ref>GOV, NOAA Office of Response and Restoration, US. [http://cameochemicals.noaa.gov/chemical/5159 "PROPYLENE OXIDE | CAMEO Chemicals | NOAA"]. ''cameochemicals.noaa.gov''.</ref>
|NFPA-H = 3
|NFPA-F = 4
|NFPA-R = 2
|FlashPtC = −37
|AutoignitionPtC = 747
|ExploLimits = 2.3–36%<ref name=PGCH/>
|PEL = TWA 100 ppm (240 mg/m<sup>3</sup>)<ref name=PGCH>{{PGCH|0538}}</ref>
|IDLH = Ca [400 ppm]<ref name=PGCH/>
|REL = Ca<ref name=PGCH/>
|LC50 = 1740 ppm (mouse, 4 h)<br/>4000 ppm (rat, 4 h)<ref name=IDLH>{{IDLH|75569|Propylene oxide}}</ref>
|LD50 = 660 mg/kg (guinea pig, oral)<br/>380 mg/kg (rat, oral)<br/>440 mg/kg (mouse, oral)<br/>1140 mg/kg (rat, oral)<br/>690 mg/kg (guinea pig, oral)<ref name=IDLH/>
|LCLo = 2005 ppm (dog, 4 h)<br/>4000 ppm (guinea pig, 4 h)<ref name=IDLH/>
}}
}}

'''Propylene oxide''' is an [[epoxide]] with the molecular formula C<sub>3</sub>H<sub>6</sub>O. This colourless [[volatility (chemistry)|volatile]] liquid with an odour similar to [[ether]], is produced on a large scale industrially. Its major application is its use for the production of [[Polyol#Polyols in polymer chemistry|polyether polyols]] for use in making [[polyurethane]] plastics. It is a [[Chirality (chemistry)|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]].

==Production==
Industrial production of propylene oxide starts from [[propylene]].<ref>{{cite journal | vauthors = Nijhuis TA, Makkee M, Moulijn JA, Weckhuysen BM |doi=10.1021/ie0513090|title=The Production of Propene Oxide: Catalytic Processes and Recent Developments|year=2006 |journal=Industrial & Engineering Chemistry Research|volume=45|issue=10|pages=3447–3459|hdl=1874/20149|hdl-access=free}}</ref> Two general approaches are employed, one involving [[Halohydrin#Synthesis|chlorohydrin formation]] and the other involving [[Redox|oxidation]].<ref name=PO>{{Ullmann| vauthors = Kahlich D, Wiechern U, Lindner J |date=2002|title=Propylene Oxide|doi=10.1002/14356007.a22_239}}</ref> 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.<ref name= Nijhuis>{{cite journal| vauthors = Nijhuis TA, Makkee M, Moulijn JA, Weckhuysen BM  |title=The Production of Propene Oxide: Catalytic Processes and Recent Developments|journal=Industrial & Engineering Chemistry Research |volume=45 |issue=10 |pages=3447–3459 |doi=10.1021/ie0513090 |year=2006 |hdl=1874/20149 |hdl-access=free}}</ref>

===Chlorohydrin route===
The traditional route proceeds via the conversion of [[propene|propylene]] to [[propylene chlorohydrin]] according to the following simplified scheme:

:[[File:Propylenoxid Darstellung 1.svg|450px]]

The mixture of 1-chloro-2-propanol and 2-chloro-1-propanol then undergoes [[Williamson ether synthesis|internal cyclization]]. For example:

:[[File:Propylenoxid Darstellung 2.svg|330px]]

[[Lime (mineral)|Lime]] ([[calcium hydroxide]]) is often used to absorb the [[HCl]].

===Oxidation of propylene===
The other general route to propylene oxide involves oxidation of propylene with an [[Organic peroxides|organic peroxide]]. The reaction follows this stoichiometry:

:CH<sub>3</sub>CH=CH<sub>2</sub>  +  RO<sub>2</sub>H  →   CH<sub>3</sub>CHCH<sub>2</sub>O  +  ROH

The process is practiced with four [[hydroperoxide]]s:<ref name= Nijhuis/>
*In the [[Halcon process]], [[tert-Butyl hydroperoxide|''t''-Butyl hydroperoxide]] derived from oxygenation of [[isobutane]], which affords [[Tert-Butanol|''t''-butanol]].  This coproduct can be dehydrated to isobutene, converted to [[MTBE]], an additive for [[gasoline]].
* [[Ethylbenzene hydroperoxide]], derived from oxygenation of [[ethylbenzene]], which affords 1-phenylethanol.  This coproduct can be dehydrated to give [[styrene]], a useful monomer.
*[[Cumene hydroperoxide]] derived from oxygenation of [[cumene]] (isopropylbenzene), which affords [[cumyl alcohol]]. Via [[dehydration reaction|dehydration]] and [[hydrogenation]] this coproduct can be recycled back to cumene.  This technology was commercialized by Sumitomo Chemical.<ref>{{cite web|url=http://nexant.ecnext.com/coms2/gi_0255-227/Developments-in-Propylene-Oxide-Technology.html|title=Summary of Sumitomo process from Nexant Reports|access-date=2007-09-18|url-status=dead|archive-url=https://archive.today/20060117092104/http://nexant.ecnext.com/coms2/gi_0255-227/Developments-in-Propylene-Oxide-Technology.html|archive-date=2006-01-17}}</ref>
*[[Hydrogen peroxide]] is the oxidant in the hydrogen peroxide to propylene oxide (HPPO) process, catalyzed by a titanium-doped [[silicalite]]:
*:C<sub>3</sub>H<sub>6</sub> + H<sub>2</sub>O<sub>2</sub> → C<sub>3</sub>H<sub>6</sub>O + H<sub>2</sub>O

In principle, this process produces only [[water]] as a [[By-product|side product]].  In practice, some ring-opened derivatives of PO are generated.<ref>{{cite journal | vauthors = Russo V, Tesser R, Santacesaria E, Di Serio M |title=Chemical and Technical Aspects of Propene Oxide Production via Hydrogen Peroxide (HPPO Process)|journal=Industrial & Engineering Chemistry Research |year=2013|volume=52|issue=3|pages=1168–1178|doi=10.1021/ie3023862}}</ref>

Propylene oxide is chiral building block that is commercially available in either enantiomeric form ((''R'')-(+) and (''S'')-(–)).  The separated enantiomers can be obtained through a Co(III)-salen-catalyzed hydrolytic [[kinetic resolution]] of the racemic material.<ref>{{Cite journal |last1=Schaus |first1=Scott E. |last2=Brandes |first2=Bridget D. |last3=Larrow |first3=Jay F. |last4=Tokunaga |first4=Makoto |last5=Hansen |first5=Karl B. |last6=Gould |first6=Alexandra E. |last7=Furrow |first7=Michael E. |last8=Jacobsen |first8=Eric N. |date=2002-02-01 |title=Highly Selective Hydrolytic Kinetic Resolution of Terminal Epoxides Catalyzed by Chiral (salen)Co III Complexes. Practical Synthesis of Enantioenriched Terminal Epoxides and 1,2-Diols |url=https://pubs.acs.org/doi/10.1021/ja016737l |journal=Journal of the American Chemical Society |language=en |volume=124 |issue=7 |pages=1307–1315 |doi=10.1021/ja016737l |pmid=11841300 |bibcode=2002JAChS.124.1307S |issn=0002-7863|url-access=subscription }}</ref>

== Reactions ==
Like other epoxides, PO undergoes ring-opening reactions.  With water, propylene glycol is produced.  With alcohols, reactions, called '''hydroxylpropylation''', analogous to [[ethoxylation]] occur.  Grignard reagents add to propylene oxide to give secondary alcohols.

Some other reactions of propylene oxide include:<ref>{{cite book | title = Dictionary of Organic Compounds | veditors = Heilbron I | date = 1953 | volume = 4 | page =[https://archive.org/details/dictionaryoforga001702mbp/page/n268 249] |publisher = Oxford University Press |url=https://archive.org/details/dictionaryoforga001702mbp}}</ref>
* Reaction with [[aluminium oxide]] at 250–260&nbsp;°C leads to [[propionaldehyde]] and a little [[acetone]].
* Reaction with [[silver(I) oxide]] leads to [[acetic acid]].
* Reaction with [[Sodium amalgam|sodium–mercury amalgam]] and water leads to [[isopropanol]].

==Uses==
Between 60 and 70% of all propylene oxide is converted to [[Polyol#Polyols in polymer chemistry|polyether polyols]] by the process called [[alkoxylation]].<ref>{{Ullmann|vauthors = Adam N, Avar G, Blankenheim H, Friedrichs W, Giersig M, Weigang E, Halfman M, Wittbecker F, Larimer D, Maier U, Meyer-Ahrens S | display-authors = 6 |date=2005|title=Polyurethanes|doi=10.1002/14356007.a21_665.pub2}}</ref>  These polyols are building blocks in the production of [[polyurethane]] plastics.<ref>{{cite web|url=http://www.dow.com/propyleneoxide/app/index.htm|title=Usage of proplyene oxide|publisher=Dow Chemical|access-date=2007-09-10|archive-url=https://web.archive.org/web/20070915135834/http://www.dow.com/propyleneoxide/app/index.htm|archive-date=2007-09-15|url-status=dead}}</ref>  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]].

===Niche uses===

====Fumigant====
The [[United States Food and Drug Administration]] has approved the use of propylene oxide to pasteurize raw [[almond]]s 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.<ref>{{cite web | title=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 | website=fda.gov | url=http://www.fda.gov/Food/GuidanceComplianceRegulatoryInformation/GuidanceDocuments/ProduceandPlanProducts/ucm169160.htm | archive-url=https://web.archive.org/web/20110209152717/http://www.fda.gov/Food/GuidanceComplianceRegulatoryInformation/GuidanceDocuments/ProduceandPlanProducts/ucm169160.htm | archive-date=2011-02-09 | url-status=dead |date=June 2009}}</ref><ref>{{cite journal|last=Agricultural Marketing Service, USDA |author-link=United States Department of Agriculture |date=30 March 2007 |title=Almonds Grown in California; Outgoing Quality Control Requirements |journal=Federal Register |volume=72 |issue=61 |pages=15,021–15,036 |url=http://www.almondboard.com/files/Rule.pdf |access-date=2007-08-22 |archive-url=https://web.archive.org/web/20070928050927/http://www.almondboard.com/files/Rule.pdf |archive-date=28 September 2007 |url-status=dead }}</ref>
[[Pistachio]] nuts can also be subjected to propylene oxide to control ''Salmonella''.

====Microscopy====
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.{{citation needed|date=January 2025}}

====Munition====
Propylene oxide is sometimes used in [[thermobaric weapons|thermobaric]] [[munitions]] as the fuel in fuel–air explosives. In addition to the explosive damage from the [[blast wave]], unexploded propylene oxide can cause additional effects from direct toxicity.<ref name=HRW1>{{cite web |url=https://www.hrw.org/en/reports/2000/02/01/backgrounder-russian-fuel-air-explosives-vacuum-bombs |title=Backgrounder on Russian Fuel Air Explosives ("Vacuum Bombs") &#124; Human Rights Watch |publisher=Hrw.org |date=February 1, 2000 |access-date=April 23, 2013 |archive-date=February 10, 2013 |archive-url=https://web.archive.org/web/20130210004254/http://www.hrw.org/en/reports/2000/02/01/backgrounder-russian-fuel-air-explosives-vacuum-bombs |url-status=dead }}</ref>

==Safety==
Propylene oxide is both acutely toxic and [[carcinogen]]ic. Acute exposure causes [[respiratory tract]] [[irritation]], eventually leading to death.<ref name="NAC/AEGL">{{cite book|author=National Research Council (US) Committee on Acute Exposure Guideline Levels|title=Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 9|chapter=Propylene Oxide Acute Exposure Guideline Levels |year=2010|publisher=National Academies Press|url=https://www.ncbi.nlm.nih.gov/books/NBK208161/}}</ref> Signs of toxicity after acute exposure include [[salivation]], [[lacrimation]], nasal discharge, gasping, lethargy and [[hypoactivity]], weakness, and incoordination. Propylene oxide is also [[Neurotoxicity|neurotoxic]] in rats, and presumably in humans.<ref>{{cite journal | vauthors = Ohnishi A, Murai Y | title = Polyneuropathy due to ethylene oxide, propylene oxide, and butylene oxide | journal = Environmental Research | volume = 60 | issue = 2 | pages = 242–247 | date = February 1993 | pmid = 8472653 | doi = 10.1006/enrs.1993.1032 | bibcode = 1993ER.....60..242O }}</ref> Propylene oxide [[Alkylation|alkylates]] [[DNA]] and is considered a mutagen for both animals and humans.<ref>{{cite journal | vauthors = Lawley PD, Jarman M | title = Alkylation by propylene oxide of deoxyribonucleic acid, adenine, guanosine and deoxyguanylic acid | journal = The Biochemical Journal | volume = 126 | issue = 4 | pages = 893–900 | date = February 1972 | pmid = 5073240 | pmc = 1178497 | doi = 10.1042/bj1260893 }}</ref><ref>{{Cite journal |last=Albertini |first=Richard J. |date=April 2003 |title=Correspondence re: Czene et al., Analysis of DNA and hemoglobin adducts and sister chromatid exchanges in a human population occupationally exposed to propylene oxide: a pilot study. Cancer Epidemiol. Biomark. Prev., 11: 315-318, 2002 |url=https://pubmed.ncbi.nlm.nih.gov/12692119/ |journal=Cancer Epidemiology, Biomarkers & Prevention |volume=12 |issue=4 |pages=388; author reply 388–389 |issn=1055-9965 |pmid=12692119}}</ref><ref>{{Cite journal |last1=Thiess |first1=A. M. |last2=Schwegler |first2=H. |last3=Fleig |first3=I. |last4=Stocker |first4=W. G. |date=1981 |title=Mutagenicity Study of Workers Exposed to Alkylene Oxides (Ethylene Oxide/Propylene Oxide) and Derivatives |url=https://www.jstor.org/stable/45005617 |journal=Journal of Occupational Medicine |volume=23 |issue=5 |pages=343–347 |jstor=45005617 |pmid=7241247 |issn=0096-1736}}</ref> Pregnant rats exposed to 500ppm of propylene oxide for less than 8 hours gave birth to litters with significant deformities and weight deficiencies. Similar exposure has also shown to reduce animal fertility.<ref name=":0">{{Cite web |last=Fishersci |date=1 July 1999 |title=Material Safety Data Sheet Propylene Oxide |url=https://fscimage.fishersci.com/msds/19910.htm |access-date=September 27, 2024 |website=Fisher Scientific}}</ref> As such, it is a known animal carcinogen<ref name="Ringo_1982" /> and potential human carcinogen, and is included into the [[List of IARC Group 2B carcinogens]].<ref name="Grana2014">{{cite journal | vauthors = Grana R, Benowitz N, Glantz SA | title = E-cigarettes: a scientific review | journal = Circulation | volume = 129 | issue = 19 | pages = 1972–1986 | date = May 2014 | pmid = 24821826 | pmc = 4018182 | doi = 10.1161/circulationaha.114.007667 }}</ref>

Propylene oxide is an extremely flammable liquid, and its vapors can form explosive mixtures with air at concentrations as low as 2.3% ([[Flammability limit|Lower Explosive Limit]]).<ref name=":0" /> Propylene oxide vapor is twice as [[Relative density|dense as air]]. When exposed to an open atmosphere, the vapor can accumulate in low-lying areas while spreading out over long distances and reach ignition source, causing [[Flash fire|flashback]] or an explosion.<ref name=":0" /><ref>{{Cite journal |last1=Wan |first1=Hangwei |last2=Wen |first2=Yuquan |last3=Zhang |first3=Qi |date=2023-01-01 |title=Explosion behaviors of vapor–liquid propylene oxide/air mixture under high-temperature source ignition |url=https://www.sciencedirect.com/science/article/abs/pii/S0016236122026424 |journal=Fuel |volume=331 |pages=125815 |doi=10.1016/j.fuel.2022.125815 |bibcode=2023Fuel..33125815W |issn=0016-2361}}</ref> When heated, propylene oxide can [[Autoacceleration|rapidly self-polymerize]] and decompose producing other toxic gases such as [[carbon monoxide]] and various [[Radical (chemistry)|free radicals]].<ref>{{Cite journal |last=HARDWICK |first=T |date=March 8, 1968 |title=Thermal decomposition of propylene oxide |url=https://cdnsciencepub.com/doi/pdf/10.1139/v68-398 |journal=Canadian Journal of Chemistry |volume=46 |issue=14 |pages=2454–2456 |doi=10.1139/v68-398 |via=Canadian Science Publishing}}</ref><ref name=":0" /> Propylene oxide fires are especially dangerous and difficult for firefighters to extinguish. In a fire, sealed tanks of propylene oxide should be cooled with fire hoses to prevent explosion from self-polymerization.<ref name=":0" /> When burning in open air however, water can transport propylene oxide outside of the fire zone which can reignite upon floating to the surface. Additional firefighting measures should be taken to prevent propylene oxide from washing out to nearby drains and sewers contaminating the surrounding environment.<ref>{{Cite web |title=Emergency Response Guide No. 127P for FLAMMABLE LIQUIDS (Water-Miscible) – HazMat Tool |url=https://www.hazmattool.com/emergencyguide.php?i=127P |access-date=2024-09-27 |website=www.hazmattool.com}}</ref><ref name=":0" />

==Natural occurrence==
In 2016 it was reported that propylene oxide was detected in [[Sagittarius B2]], a cloud of gas in the [[Milky Way (galaxy)|Milky Way]] weighing three million [[solar mass]]es.  It is the first [[Chirality (chemistry)|chiral]] molecule to be detected in space, albeit with no [[enantiomeric excess]].<ref>{{cite web|url=http://www.sciencealert.com/scientists-just-detected-this-life-forming-molecule-in-interstellar-space-for-the-first-time|title=Scientists just detected this life-forming molecule in interstellar space for the first time|publisher=Science Alert|date=2016-06-15}}</ref>

== References ==
{{Reflist|refs=
<ref name=Ringo_1982>{{cite journal | vauthors = Ringo DL, Brennan EF, Cota-Robles EH | title = Epoxy resins are mutagenic: implications for electron microscopists | journal = Journal of Ultrastructure Research | volume = 80 | issue = 3 | pages = 280–287 | date = September 1982 | pmid = 6752439 | doi = 10.1016/s0022-5320(82)80041-5 }}</ref>
}}

==Cited sources==
*{{RubberBible92nd|name-list-style = vanc }}

== External links ==
* [http://webbook.nist.gov/cgi/cbook.cgi?ID=C75569 WebBook page for C3H6O]
* [http://www.epa.gov/ttn/atw/hlthef/prop-oxi.html Propylene oxide] at the [[United States Environmental Protection Agency]]
* [http://chemindustry.ru/Propylene_Oxide.php Propylene oxide – chemical product info: properties, production, applications.]
* [https://web.archive.org/web/20081204112403/http://pubweb.epa.gov/ttn/atw/orig189.html Propylene oxide] at the Technology Transfer Network Air Toxics Web Site
* [https://www.cdc.gov/niosh/npg/npgd0538.html CDC – NIOSH Pocket Guide to Chemical Hazards]

{{Authority control}}

[[Category:Epoxides]]
[[Category:IARC Group 2B carcinogens]]
[[Category:Commodity chemicals]]