Propylene oxide

Last updated
Propylene oxide
Propylene oxide.svg
(S)-Propylene oxide molecule ball.png
Names
Preferred IUPAC name
(2R)-2-Methyloxirane
(2S)-2-Methyloxirane
Other names
Propylene oxide
Epoxypropane
Propylene epoxide
1,2-Propylene oxide
Methyl oxirane
1,2-Epoxypropane
Propene oxide
Methyl ethylene oxide
Methylethylene oxide
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.000.800 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 200-879-2
KEGG
PubChem CID
UNII
  • InChI=1S/C3H6O/c1-3-2-4-3/h3H,2H2,1H3
    Key: GOOHAUXETOMSMM-UHFFFAOYSA-N
  • CC1CO1
Properties
C3H6O
Molar mass 58.080 g·mol−1
AppearanceColourless 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]
−4.25×10−5 cm3/mol [3]
1.3660 [2]
Thermochemistry
120.4 J·(K·mol)−1
Std molar
entropy (S⦵298)
196.5 J·(K·mol)−1
−123.0 kJ·mol−1 [4]
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
Extremely flammable [5] [6]
GHS labelling:
GHS-pictogram-flamme.svg GHS-pictogram-silhouette.svg GHS-pictogram-exclam.svg
Danger
NFPA 704 (fire diamond)
NFPA 704.svgHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 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. propaneInstability 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g. white phosphorusSpecial hazards (white): no code
3
4
2
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]
NIOSH (US health exposure limits):
PEL (Permissible)
TWA 100 ppm (240 mg/m3) [1]
REL (Recommended)
Ca [1]
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).
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Propylene oxide is an acutely toxic and carcinogenic organic compound with the molecular formula C3H6O. This colourless 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 polyether polyols for use in making polyurethane plastics. It is a chiral epoxide, although it is commonly used as a racemic mixture.

Contents

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. [8] Two general approaches are employed, one involving hydrochlorination and the other involving oxidation. [9] 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. [10]

Hydrochlorination route

The traditional route proceeds via the conversion of propene to propylene chlorohydrin according to the following simplified scheme:

Propylenoxid Darstellung 1.svg

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

Propylenoxid Darstellung 2.svg

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 peroxide. The reaction follows this stoichiometry:

CH3CH=CH2 + RO2H → CH3CHCH2O + ROH

The process is practiced with four hydroperoxides: [10]

In principle, this process produces only water as a side product. In practice, some ring-opened derivatives of PO are generated. [12]

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. [13]

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: [14]

Uses

Between 60 and 70% of all propylene oxide is converted to polyether polyols by the process called alkoxylation. [15] These polyols are building blocks in the production of polyurethane plastics. [16] 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 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. [17] [18] 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.

Munition

Propylene oxide is sometimes used in 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. [19]

Safety

Propylene oxide is both acutely toxic and carcinogenic. Acute exposure causes respiratory tract irritation, eventually leading to death. [20] Signs of toxicity after acute exposure include salivation, lacrimation, nasal discharge, gasping, lethargy and hypoactivity, weakness, and incoordination. Propylene oxide is also neurotoxic in rats, and presumably in humans [21] Propylene oxide alkylates DNA and is considered a mutagen for both animals and humans. [22] [23] [24] 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. [25] As such, it is a known animal carcinogen [26] and potential human carcinogen, and is included into the List of IARC Group 2B carcinogens. [27]

Propylene oxide is an extremely flammable liquid, and its vapors can form explosive mixtures with air at concentrations as low as 2.3% (Lower Explosive Limit). [25] Propylene oxide vapor is twice as 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 flashback or an explosion. [25] [28] When heated, propylene oxide can rapidly self-polymerize and decompose producing other toxic gases such as carbon monoxide and various free radicals. [29] [25] 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. [25] 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. [30] [25]

Natural occurrence

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, albeit with no enantiomeric excess. [31]

Related Research Articles

<span class="mw-page-title-main">Ether</span> Organic compounds made of alkyl/aryl groups bound to oxygen (R–O–R)

In organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom bonded to two organyl groups. They have the general formula R−O−R′, where R and R′ represent the organyl groups. Ethers can again be classified into two varieties: if the organyl groups are the same on both sides of the oxygen atom, then it is a simple or symmetrical ether, whereas if they are different, the ethers are called mixed or unsymmetrical ethers. A typical example of the first group is the solvent and anaesthetic diethyl ether, commonly referred to simply as "ether". Ethers are common in organic chemistry and even more prevalent in biochemistry, as they are common linkages in carbohydrates and lignin.

<span class="mw-page-title-main">Phenol</span> Organic compound (C6H5OH)

Phenol is an aromatic organic compound with the molecular formula C6H5OH. It is a white crystalline solid that is volatile. The molecule consists of a phenyl group bonded to a hydroxy group. Mildly acidic, it requires careful handling because it can cause chemical burns.

<span class="mw-page-title-main">Petrochemical</span> Chemical product derived from petroleum

Petrochemicals are the chemical products obtained from petroleum by refining. Some chemical compounds made from petroleum are also obtained from other fossil fuels, such as coal or natural gas, or renewable sources such as maize, palm fruit or sugar cane.

<span class="mw-page-title-main">Ethylene glycol</span> Organic compound ethane-1,2-diol

Ethylene glycol is an organic compound with the formula (CH2OH)2. It is mainly used for two purposes: as a raw material in the manufacture of polyester fibers and for antifreeze formulations. It is an odorless, colorless, flammable, viscous liquid. It has a sweet taste, but is toxic in high concentrations. This molecule has been observed in outer space.

<span class="mw-page-title-main">Butanone</span> Chemical compound

Butanone, also known as methyl ethyl ketone (MEK) or ethyl methyl ketone, is an organic compound with the formula CH3C(O)CH2CH3. This colorless liquid ketone has a sharp, sweet odor reminiscent of acetone. It is produced industrially on a large scale, but occurs in nature only in trace amounts. It is partially soluble in water, and is commonly used as an industrial solvent. It is an isomer of another solvent, tetrahydrofuran.

<span class="mw-page-title-main">Cumene process</span> Industrial process

The cumene process is an industrial process for synthesizing phenol and acetone from benzene and propylene. The term stems from cumene, the intermediate material during the process. It was invented by R. Ūdris and P. Sergeyev in 1942 (USSR), and independently by Heinrich Hock in 1944.

Acrylonitrile is an organic compound with the formula CH2CHCN and the structure H2C=CH−C≡N. It is a colorless, volatile liquid. It has a pungent odor of garlic or onions. Its molecular structure consists of a vinyl group linked to a nitrile. It is an important monomer for the manufacture of useful plastics such as polyacrylonitrile. It is reactive and toxic at low doses.

<span class="mw-page-title-main">Epoxide</span> Organic compounds with a carbon-carbon-oxygen ring

In organic chemistry, an epoxide is a cyclic ether, where the ether forms a three-atom ring: two atoms of carbon and one atom of oxygen. This triangular structure has substantial ring strain, making epoxides highly reactive, more so than other ethers. They are produced on a large scale for many applications. In general, low molecular weight epoxides are colourless and nonpolar, and often volatile.

A diol is a chemical compound containing two hydroxyl groups. An aliphatic diol may also be called a glycol. This pairing of functional groups is pervasive, and many subcategories have been identified. They are used as protecting groups of carbonyl groups, making them essential in synthesis of organic chemistry.

Propylene, also known as propene, is an unsaturated organic compound with the chemical formula CH3CH=CH2. It has one double bond, and is the second simplest member of the alkene class of hydrocarbons. It is a colorless gas with a faint petroleum-like odor.

<span class="mw-page-title-main">Cyclohexanol</span> Chemical compound

Cyclohexanol is the organic compound with the formula HOCH(CH2)5. The molecule is related to cyclohexane by replacement of one hydrogen atom by a hydroxyl group. This compound exists as a deliquescent colorless solid with a camphor-like odor, which, when very pure, melts near room temperature. Millions of tonnes are produced annually, mainly as a precursor to nylon.

<span class="mw-page-title-main">Hydroquinone</span> Chemical compound

Hydroquinone, also known as benzene-1,4-diol or quinol, is an aromatic organic compound that is a type of phenol, a derivative of benzene, having the chemical formula C6H4(OH)2. It has two hydroxyl groups bonded to a benzene ring in a para position. It is a white granular solid. Substituted derivatives of this parent compound are also referred to as hydroquinones. The name "hydroquinone" was coined by Friedrich Wöhler in 1843.

<span class="mw-page-title-main">Cyclohexanone</span> Chemical compound

Cyclohexanone is the organic compound with the formula (CH2)5CO. The molecule consists of six-carbon cyclic molecule with a ketone functional group. This colorless oily liquid has a sweet odor reminiscent of benzaldehyde. Over time, samples of cyclohexanone assume a pale yellow color. Cyclohexanone is slightly soluble in water and miscible with common organic solvents. Millions of tonnes are produced annually, mainly as a precursor to nylon.

<span class="mw-page-title-main">Cumene</span> Chemical compound

Cumene (isopropylbenzene) is an organic compound that contains a benzene ring with an isopropyl substituent. It is a constituent of crude oil and refined fuels. It is a flammable colorless liquid that has a boiling point of 152 °C. Nearly all the cumene that is produced as a pure compound on an industrial scale is converted to cumene hydroperoxide, which is an intermediate in the synthesis of other industrially important chemicals, primarily phenol and acetone.

Autoxidation refers to oxidations brought about by reactions with oxygen at normal temperatures, without the intervention of flame or electric spark. The term is usually used to describe the gradual degradation of organic compounds in air at ambient temperatures. Many common phenomena can be attributed to autoxidation, such as food going rancid, the 'drying' of varnishes and paints, and the perishing of rubber. It is also an important concept in both industrial chemistry and biology. Autoxidation is therefore a fairly broad term and can encompass examples of photooxygenation and catalytic oxidation.

<span class="mw-page-title-main">Hydroperoxide</span> Class of chemical compounds

Hydroperoxides or peroxols are compounds of the form ROOH, where R stands for any group, typically organic, which contain the hydroperoxy functional group. Hydroperoxide also refers to the hydroperoxide anion and its salts, and the neutral hydroperoxyl radical (•OOH) consist of an unbond hydroperoxy group. When R is organic, the compounds are called organic hydroperoxides. Such compounds are a subset of organic peroxides, which have the formula ROOR. Organic hydroperoxides can either intentionally or unintentionally initiate explosive polymerisation in materials with unsaturated chemical bonds.

<i>tert</i>-Butyl hydroperoxide Chemical compound

tert-Butyl hydroperoxide (tBuOOH) is the organic compound with the formula (CH3)3COOH. It is one of the most widely used hydroperoxides in a variety of oxidation processes, like the Halcon process. It is normally supplied as a 69–70% aqueous solution. Compared to hydrogen peroxide and organic peracids, tert-butyl hydroperoxide is less reactive and more soluble in organic solvents. Overall, it is renowned for the convenient handling properties of its solutions. Its solutions in organic solvents are highly stable.

Isopropyl alcohol is a colorless, flammable organic compound with a pungent alcoholic odor.

<span class="mw-page-title-main">Cumene hydroperoxide</span> Aromatic organic chemical compound

Cumene hydroperoxide is the organic compound with the formula C6H5C(CH3)2OOH. An oily liquid, it is classified as an organic hydroperoxide. Products of decomposition of cumene hydroperoxide are methylstyrene, acetophenone, and 2-phenyl-2-propanol.

Alkoxylation is a chemical reaction that involves the addition of an epoxide to another compound. The usual manifestation of this reaction is ethoxylation of alcohols (ROH), in which case ethylene oxide is the alkoxylating agent:

References

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  2. 1 2 3 4 Haynes 2011, p. 3.384
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  8. ↑ Nijhuis TA, Makkee M, Moulijn JA, Weckhuysen BM (2006). "The Production of Propene Oxide: Catalytic Processes and Recent Developments". Industrial & Engineering Chemistry Research. 45 (10): 3447–3459. doi:10.1021/ie0513090. hdl: 1874/20149 .
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  11. ↑ "Summary of Sumitomo process from Nexant Reports". Archived from the original on 2006-01-17. Retrieved 2007-09-18.
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  14. ↑ Heilbron I, ed. (1953). Dictionary of Organic Compounds. Vol. 4. Oxford University Press. p.  249.
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  17. ↑ "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". fda.gov. June 2009. Archived from the original on 2011-02-09.
  18. ↑ 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.
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  31. ↑ "Scientists just detected this life-forming molecule in interstellar space for the first time". Science Alert. 2016-06-15.

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