Propylene glycol 228900 223234744 2008-07-03T04:51:20Z Scottpartlin 7413724 /* See also */ {{Chembox new | Reference = <ref>''[[Merck Index]]'', 11th Edition, '''7868'''.</ref> | Name = '''Propylene glycol''' | ImageFile = Propylene glycol chemical structure.png | ImageSize = 200px | ImageName = Propylene glycol | ImageFileR1 = PropyleneGlycol-spaceFill.png | ImageSizeR1 = 100px | ImageNameR1 = Space-filling model | ImageFileL1 = PropyleneGlycol-stickAndBall.png | ImageSizeL1 = 100px | ImageNameL1 = ball-and-stick model | IUPACName = propane-1,2-diol | OtherNames = propylene glycol | Section1 = {{Chembox Identifiers | CASNo = 57-55-6 | SMILES = CC(O)CO | RTECS = TY6300000 }} | Section2 = {{Chembox Properties | Formula = C<sub>3</sub>H<sub>8</sub>O<sub>2</sub> | MolarMass = 76.09 g/mol | Density = 1.036 g/cm³ | MeltingPt = -59 °C | Solubility = fully [[miscible]] | Solubility1 = fully [[miscible]] | Solvent1 = ethanol | Solubility2 = fully [[miscible]] | Solvent2 = diethyl ether | Solubility3 = fully [[miscible]] | Solvent3 = acetone | Solubility4 = fully [[miscible]] | Solvent4 = chloroform | BoilingPt = 188.2 °C | ThermalConductivity = {{{conductivity|0.34}}} W/m-K (50% H2O @ 90°C) }} | Section7 = {{Chembox Hazards | ExternalMSDS = [http://www.jtbaker.com/msds/englishhtml/p6928.htm External MSDS] | NFPA-H = 0 | NFPA-F = 1 | NFPA-R = 0 | NFPA-O = | RPhrases = | SPhrases = {{S24}} {{S25}} }} | Section8 = {{Chembox Related | Function = [[glycol]]s | OtherFunctn = [[Ethylene glycol]] }} }} '''Propylene glycol''', known also by the systematic name propane-1,2-diol, is an [[organic compound]] (a [[diol]] [[alcohol]]), usually a faintly sweet, odorless, and colorless clear viscous liquid that is [[hygroscopic]] and [[miscible]] with [[water]], [[acetone]], and [[chloroform]]. ==Chirality== Propylene glycol contains an asymmetrical carbon atom, so it exists in two [[stereoisomer]]s. The commercial product is a [[racemic]] mixture. Pure optical isomers can be obtained by hydration of optically pure propylene oxide.<ref>{{cite web|url=http://chemindustry.ru/1,2-Propanediol.php|title = 1,2-Propanediol|publisher=ChemIndustry.ru|accessdate=2007-12-28}}</ref> ==Production== Industrially propylene glycol is produced by [[propylene oxide]] hydration. Different manufacturers use non-catalytic high-temperature process at 200-220 °C or catalytic route which proceeds at 150-180 °C in presence of ion exchange resin or small amounts of sulfuric acid or alkali. Final products contain 20% 1,2-propanediol, 1.5% of dipropylene glycol and small amount of other polypropylene glycol.<ref>[http://chemindustry.ru/1,2-Propanediol.php 1,2-propanediol: chemical product info at CHEMINDUSTRY.RU<!-- Bot generated title -->]</ref> Propylene glycol can also be converted from [[glycerol]], a [[biodiesel]] byproduct. ==Applications== Propylene glycol is used: * As a [[moisturizer]] in [[medication|medicines]], [[cosmetics]], [[food]], [[toothpaste]], [[mouth wash]], and [[tobacco]] products * As a medical and sexual [[lubricant]] (A.K.A. "[[personal lubricant]]") * As an [[emulsification]] agent in [[angostura]] and orange [[bitters]] * As a [[solvent]] for [[Food coloring|food colors]] and [[flavoring]]s * As a [[humectant]] [[food additive]], labeled as [[E number]] E1520 * As a carrier in [[fragrance oil]]s * As a less-[[poison|toxic]] [[antifreeze]] * As a [[solvent]] used in mixing photographic chemicals, such as film developers * In [[smoke machine]]s to make artificial [[smoke]] for use in [[firefighter]]s' training and [[theater|theatrical]] productions * In [[e-cigarette|electronic cigarettes]] to make the produced vapor better resemble cigarette smoke * In hand sanitizers, [[Antiseptic|antibacterial]] lotions, and [[saline solution]]s * In [[cryonics]] * As a working fluid in hydraulic presses * As a [[coolant]] in liquid cooling systems * To regulate humidity in a cigar [[humidor]] * As the killing and preserving agent in pitfall traps, usually used to capture [[ground beetles]] * To treat livestock [[ketosis]] * As the main ingredient in [[deodorant]] sticks. * As an ingredient in Romney's Kendal Mint Cake Propylene glycol has similar properties as ethylene glycol (MEG). The industrial norm is to replace ethylene glycol by propylene glycol. ==Safety== Cases of propylene glycol poisoning are related to either inappropriate intravenous use or accidental ingestion by children.<ref>National Library of Medicine;. Human Toxicity Excerpts: CAS Registry Number: 57-55-6 (1,2-Propylene Glycol). Selected toxicity information from HSDB. 2005. </ref> The oral toxicity of propylene glycol is very low. In one study, rats were provided with feed containing as much as 5% PG over a period of 104 weeks and they showed no apparent ill effects.<ref>Gaunt, IF, Carpanini, FMB, Grasso, P and Lansdown, ABG, Long-term toxicity of propylene glycol in rats, Food and Cosmetics Toxicology, Apr. 1972, 10(2), pages 151 - 162. </ref> Because of its low chronic oral toxicity, propylene glycol is [[generally recognized as safe]] (GRAS) for use as a direct food additive. Serious toxicity will occur only at extremely high intakes over a relatively short period of time that result in plasma concentrations of over 4 g/L.<ref>Flanagan RJ;Braithwaite RA;Brown SS;Widdop B;de Wolff FA;. The International Programme on Chemical Safety: Basic Analytical Toxicology. WHO, 1995.</ref> Such levels of ingestion would not be possible when consuming reasonable amounts of a food product or dietary supplements containing ''at most'' 1 g/kg propylene glycol. The U.S. [[Food and Drug Administration]] (FDA) has determined propylene glycol to be "[[generally recognized as safe]]" for use in food, cosmetics, and medicines. Like [[ethylene glycol]], propylene glycol affects the body's chemistry by increasing the amount of acid. Propylene glycol is metabolized into [[pyruvic acid]], which is a normal metabolite in the breakdown of glucose, while ethylene glycol is metabolized into [[oxalic acid]], which is toxic. However, propylene glycol is not approved for use in cat food. The U.S. Food and Drug Administration has determined that propylene glycol in or on cat food has not been shown by adequate scientific data to be safe for use. Use of propylene glycol in or on cat food causes the feed to be adulterated and in violation of the Federal Food, Drug, and Cosmetic Act. 21CFR589.1001 Prolonged contact with propylene glycol is essentially non-irritating to the skin. Undiluted propylene glycol is minimally irritating to the eye, and can produce slight transient conjunctivitis (the eye recovers after the exposure is removed). Exposure to mists may cause eye irritation, as well as upper respiratory tract irritation.<ref>Dow Propylene Glycol Industrial Safety Data Sheet (http://www.dow.com/PublishedLiterature/dh_0361/09002f1380361176.pdf?filepath=propyleneglycol/pdfs/noreg/117-01515.pdf&fromPage=GetDoc), No. 248, November 17, 2003, page 1. </ref> Inhalation of the propylene glycol vapors appears to present no significant hazard in ordinary applications. However, limited human experience indicates that inhalation of propylene glycol mists could be irritating to some individuals. Therefore inhalation exposure to mists of these materials should be avoided. Some research has suggested that propylene glycol not be used in applications where inhalation exposure or human eye contact with the spray mists of these materials is likely, such as fogs for theatrical productions or antifreeze solutions for emergency eye wash stations.<ref>A Guide to Glycols (http://www.dow.com/PublishedLiterature/dh_02aa/09002f13802aaf25.pdf), page 36.</ref> Propylene glycol does not cause sensitization and it shows no evidence of being a carcinogen or of being genotoxic.<ref>1,2-Dihydroxypropane SIDS Initial Assessment Profile (http://www.chem.unep.ch/irptc/sids/OECDSIDS/57-55-6.pdf), UNEP Publications, SIAM 11, U.S.A, January 23-26, 2001, page 21.</ref><ref>Title 21, U.S. Code of Federal Regulations. 1999. </ref> Recent Clinical Journal of Medicine article states two cases of adult men experiencing psychosis from use of propylene glycol used in phenytoin injection USP. Both patients had to be switched to Cerebyx (Fosphenytoin Sodium) in order to avoid propylene glycol co-solvent. Research has suggested that individuals who cannot tolerate propylene glycol probably experience a special form of irritation, but that they only rarely develop allergic contact dermatitis. Other investigators believe that the incidence of allergic contact dermatitis to propylene glycol may be greater than 2% in patients with eczema.<ref>[American Medical Association, Council on Drugs. AMA Drug Evaluations Annual 1994. Chicago, IL: American Medical Association, 1994., p. 1224]</ref> Patients with [[vulvodynia]] and [[interstitial cystitis]] may be especially sensitive to propylene glycol. Women struggling with yeast infections may also notice that some OTC creams can cause intense burning.<ref>Elizabeth Vliet MD, Screaming To Be Heard: Hormonal Connections That Women Suspect and Doctors Ignore". M. Evans and Company, Inc. New York 1995</ref>Post menopausal women who require the use of an estrogen cream may notice that brand name creams made with propylene glycol often create extreme, uncomfortable burning along the vulva and perianal area. In these cases, patients can request that a local compounding pharmacy make a "propylene glycol free" cream which is much more tolerable.{{Fact|date=March 2008}} ==References== <references/> ==See also== * [[Ethylene glycol]] * [[1,3-Propanediol]] ==External links== * [http://www.atsdr.cdc.gov/csem/egpg/ ATSDR - Case Studies in Environmental Medicine: Ethylene Glycol and Propylene Glycol Toxicity] U.S. [[Department of Health and Human Services]] (public domain) * [http://www.dow.com/propyleneglycol/prod/pguspep.htm Propylene Glycol info at DOW Chemical] * [http://www.lyondell.com/Lyondell/Products/ByMarket/Pharmaceuticals/ExcepientSolubilizer/Propylene+GlycolUSPEP/ Propylene Glycol at Lyondell Chemical] * [http://www.scorecard.org/chemical-profiles/summary.tcl?edf_substance_id=57-55-6 Propylene Glycol info at Scorecard.com] * [http://chemindustry.ru/1,2-Propanediol.php Propylene Glycol - chemical product info: properties, production, applications.] [[Category:Alcohols]] [[Category:Polyols]] [[Category:Household chemicals]] [[Category:Alcohol solvents]] [[Category:Cosmetic chemicals]] [[Category:Food additives]] [[de:Propylenglykol]] [[et:Propüleenglükool]] [[es:Propilenglicol]] [[fr:Propylène glycol]] [[lv:1,2-propāndiols]] [[nl:Propyleenglycol]] [[ja:プロピレングリコール]] [[fi:Propyleeniglykoli]] [[pt:Propilenoglicol]] [[zh:丙二醇]]