Glycerol: Difference between revisions
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{{redirect4|Glycerine|Glycerin|the Bush song|[[Glycerine (song)]]}} |
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{{Chembox new |
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| Name = Glycerol |
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| ImageFileL1 = Glycerin_Skelett.svg |
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| ImageSizeL1 = 120px |
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| ImageNameL1 = Glycerol |
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| ImageFileR1 = Glycerol-3D-balls.png |
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| ImageSizeR1 = 120px |
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| ImageNameR1 = Ball-and-stick model of glycerol |
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| ImageFile2 = Glycerol-3D-vdW.png |
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| ImageSize2 = 150px |
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| ImageName2 = Space-filling model of glycerol |
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| IUPACName = Propane-1,2,3-triol |
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| OtherNames = glycerin<br /> glycerine<br /> propane-1,2,3-triol<br /> 1,2,3-propanetriol<br /> 1,2,3-trihydroxypropane<br /> glyceritol<br /> glycyl alcohol |
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| Section1 = {{Chembox Identifiers |
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| CASNo = 56-81-5 |
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| ChemSpiderID = 733 |
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| SMILES = OCC(O)CO |
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}} |
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| Section2 = {{Chembox Properties |
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| Formula = C<sub>3</sub>H<sub>5</sub>(OH)<sub>3</sub> |
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| MolarMass = 92.09382 g/mol |
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| Density = 1.261 g/cm³ |
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| Viscosity = 1.5 Pa·s |
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| MeltingPt = 18 °C (64.4°F) |
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| BoilingPt = 290 °C (554°F) |
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}} |
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| Section7 = {{Chembox Hazards |
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| NFPA-H = 1 |
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| NFPA-F = 1 |
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| NFPA-R = 0 |
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| NFPA-O = |
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| FlashPt = 160 °C (closed cup)}} |
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}} |
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'''Glycerol''' is a [[chemical compound]] also commonly called '''glycerin''' or '''glycerine'''. It is a colorless, odorless, [[Viscosity|viscous]] liquid that is widely used in pharmaceutical formulations. For human consumption, Glycerol is classified by the FDA among the [[sugar alcohol]]s as a caloric macronutrient. Glycerol has three [[hydrophilic]] [[hydroxyl group]]s that are responsible for its solubility in [[water]] and its [[Hygroscopy|hygroscopic]] nature. Its surface tension is 64.00 mN/m at 20 °C , and it has a temperature coefficient of -0.0598 mN/(m K). The glycerol substructure is a central component of many [[lipid]]s. Glycerol is sweet-tasting and of low toxicity. |
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==Synthesis and production== |
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[[Image:Glycerol-3DModel.png|thumb|left|Glycerol (3D model), showing the atoms and the lone electron pairs associated with the oxygen atoms (in pink)]] |
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Since glycerol forms the backbone of [[triglyceride]]s, it is produced on [[saponification]] or [[transesterification]]. [[Soap#soapmaking|Soap-making]] and [[biodiesel]] production are respective examples. |
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Glycerol is a 10% by-product of [[biodiesel production]] (via the transesterification of vegetable oils or animal fats). This has led to an excess of crude glycerol in the market, making the epichlorohydrin process no longer economical. |
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Current levels of glycerol production are running at about 350,000 tons per annum in the USA, and 600,000 tpa in Europe. This will increase as it implements [[Directive on the Promotion of the use of biofuels and other renewable fuels for transport|EU directive 2003/30/EC]] which requires replacement of 5.75% of petroleum fuels with biofuel across all Member States by 2010<ref>[http://www.theglycerolchallenge.org/ The Glycerol Challenge]</ref>. |
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Dr. Edman Tsang and his research group at Oxford's Department of Chemistry recently (2008) developed a potential solution by converting glycerol and hydrogen into methanol at low temperature (100 degrees celcius) and pressure (20 bar). |
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<br clear = left/> |
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==Applications== |
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In foods and beverages, glycerol serves as a [[humectant]], solvent and sweetener, and may help preserve foods. It is also used as filler in commercially prepared low-fat foods (e.g., [[cookie]]s), and as a [[thickening agent]] in [[liqueur]]s. Glycerol also serves as a way, along with water, to preserve certain types of leaves. Glycerol is also used as a sugar substitute. In this regard, it has approximately 27 calories per teaspoon and is 60% as sweet as [[sucrose]]. Although it has about the same [[food energy]] as table sugar, it does not raise [[blood sugar]] levels, nor does it feed the bacteria that form plaques and cause dental cavities. As a food additive, glycerol is also known as [[E number]] E422. |
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In [[organic synthesis]], glycerol is used as a readily available [[prochiral]] building block. |
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Glycerin can also serve as a substitute for petroleum based products. Glycerin derived [[epichlorohydrin]] and [[propylene glycol]] are substitutes for petroleum-based [[Polypropylene]]. |
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===Categorization=== |
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Glycerol is currently categorized by the American Dietetic Association as a carbohydrate. The FDA carbohydrate designation includes all caloric macronutrients excluding protein and fat. This group includes indigestible fibers, but not ash. Glycerin has a caloric density similar to table sugar, but a lower [[glycemic index]] and different metabolic pathway within the body, so some dietary advocates accept glycerin as a sweetener compatible with "low carb" diets.<!-- cribbing wildly from the original nonsense, with extensive rant on talk page --> |
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===Feedstock=== |
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It is one of the major raw materials for the manufacture of [[polyol]]s for flexible foams, and to a lesser extent rigid [[polyurethane]] foams.<!--Is it the other way around? Glycerol is the initiator to which propylene oxide/ethylene oxide is added--> |
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Glycerol is used to produce [[nitroglycerin]], which is an essential ingredient of smokeless gunpowder and various munitions. Reliance on soap-making to supply co-product glycerine made it difficult to increase production to meet wartime demand. Hence, synthetic glycerin processes were national defence priorities in the days leading up to World War II. |
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Glycerol is also used to manufacture mono- and di-glycerides for use as [[emulsifier]]s, as well as polyglycerol [[ester]]s going into [[shortening]]s and [[margarine]]. |
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===Research laboratory usage=== |
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Glycerol is a common component of solvents for enzymatic reagents stored at temperatures below zero degrees Celsius due to the depression of the freezing temperature of solutions with high concentrations of glycerol. It is also dissolved in water to reduce damage by ice crystals to laboratory organisms that are stored in frozen solutions, such as bacteria, nematodes, and fruit flies. Samples are loaded into agarose gel electrophoresis mixed in loading buffers that mainly consist of glycerol; when the sample is injected into wells, the glycerol causes the solution to sink through the running buffer to the bottom of the well. |
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===Pharmaceutical and personal care applications=== |
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Glycerol is used in [[medicine|medical]] and [[pharmaceutical]] and [[personal care]] preparations, mainly as a means of improving smoothness, providing [[lubrication]] and as a [[humectant]]. It is found in [[cough syrup]]s, elixirs and [[expectorant]]s, [[toothpaste]], [[mouthwash]]es, [[skin care]] products, shaving cream, [[hair care]] products, and [[soap]]s. |
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As a 10% solution, glycerol prevents tannins from precipitating in ethanol extracts of plants ([[tinctures]]). It is also used as a substitute for ethanol as a solvent in preparing herbal extractions. It is less extractive and is approximately 30% less able to be absorbed by the body. [[Fluid extract]] manufacturers often extract herbs in hot water before adding glycerin to make [[glycerites]].<ref> |
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Walter S. Long. ''The Composition of Commercial Fruit Extracts'' Transactions of the Kansas Academy of Science (1903-), Vol. 28, Jan. 14, 1916 - Jan. 13, 1917 (Jan. 14, 1916 - Jan. 13, 1917), pp. 157-161 doi:10.2307/3624347</ref><ref>[[David Winston]] www.herbaltherapeutics.com</ref><ref>[http://www.newhope.com/nutritionsciencenews/NSN_backs/Apr_99/backtalk.cfm Does Alcohol Belong In Herbal Tinctures?<!-- Bot generated title -->]</ref> |
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Used as a [[laxative]] when introduced into the rectum in [[suppository]] or liquid ([[enema]]) form; irritates the bowel and induces a [[laxative#Hydrating agents (osmotics)|hyperosmotic effect]]. |
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Glycerol is a component of glycerol [[soap]], which is made from [[denatured alcohol]], glycerol, sodium castorate (from [[Castor bean|castor]]), [[sodium cocoate]], [[sodium tallowate]], [[sucrose]], water, and [[parfum]] ([[fragrance]]). Sometimes one adds [[sodium laureth sulfate]]. This kind of soap is used by people with sensitive, easily-irritated [[skin]] because it prevents skin dryness with its [[wiktionary:moisturize|moisturizing]] properties. It is possible to make glycerol soap at home. |
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It is also used in de-/anti-icing fluids, as in [[vitrification]] of blood cells for storage in [[liquid nitrogen]] |
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In motion-picture production, glycerol is used as a non-evaporating substitute for perspiration on actors. It is also used in the formulation of some types of stage blood. |
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===Potential uses=== |
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A great deal of research is being conducted to try to make value-added molecules from crude glycerol (typically containing 20 % water and residual esterification catalyst) obtained from biodiesel production, as an alternative to disposal by [[incineration]]. One such program to add value to this glut of glycerol is the UK-based initiative [http://www.theglycerolchallenge.org The Glycerol Challenge]. Some potential uses for glycerol include the following: |
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*Hydrogen gas production unit<ref>{{cite journal | author = A. T. Marshall and R. G. Haverkamp | title = Production of Hydrogen by the Electrochemical Reforming of Glycerol-Water solutions in a PEM electrolysis cell | year = 2008 | journal = [[International Journal of Hydrogen Energy]] | volume = 33 | issue = 17 | pages = 4649-4654 | doi = 10.1016/j.ijhydene.2008.05.029}}</ref> |
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*[[Glycerine acetate]] (as a potential fuel additive)<ref>{{cite journal | author = J. A. Melero, R. vanGrieken, G. Morales and M. Paniagua | title = Acidic Mesoporous Silica for the Acetylation of Glycerol: Synthesis of Bioadditives to Petrol Fuel | year = 2007 | journal = [[Energy Fuels]] | volume = 21 | issue = 3 | pages = 1782–1791 | doi = 10.1021/ef060647q}}</ref> |
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*Compost additive |
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*For [[Tincture]] extraction and preservation of Essential oils and chemicals from herbs. |
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*Citric acid production |
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*Cosmetic bonding agent for makeup, including: eye shadow, lipstick, lipgloss, and lotions and also including eyedrops as well |
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*Can be used to moisten [[hookah]] tobacco if it's too dry or bought as "dry" tobacco.. |
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*Conversion to [[propylene glycol]]<ref>{{cite press release | title = Dow Achieves Another Major Milestone in its Quest for Sustainable Chemistries |date=15 March 2007 | publisher = [[Dow Chemical Company]] | url = http://www.dow.com/propyleneglycol/news/20070315b.htm}}</ref>. |
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*Conversion to [[acrolein]]<ref>{{cite journal | author = L. Ott, M. Bicker and H. Vogel | doi = 10.1039/b506285c | title = The catalytic dehydration of glycerol in sub- and supercritical water: a new chemical process for acrolein production | [[Green Chemistry (journal)|Green Chemistry]] | volume = 8 | issue = 2 | pages = 214–220 | year = 2006 | journal = Green Chemistry}}</ref><ref>{{cite journal | author = Watanabe, M. et al | title = Acrolein synthesis from glycerol in hot-compressed water | journal = [[Bioresource Technology]] | year = 2007 | volume = 98 | pages = 1285–1290 | doi = 10.1016/j.biortech.2006.05.007}}</ref> |
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* Conversion to [[ethanol]]<ref name = Yazdani>{{cite journal | author = S. S. Yazdani and R. Gonzalez | title = Anaerobic fermentation of glycerol: a path to economic viability for the biofuels industry | year = 2007 | journal = [[Current Opinion in Biotechnology]] | volume = 18 | issue = 3 | pages = 213–219 | doi = 10.1016/j.copbio.2007.05.002 | laysummary = http://www.sciencedaily.com/releases/2007/06/070626115246.htm | laysource = ScienceDaily | laydate = 27 Jun 2007}}</ref> |
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*Conversion to [[epichlorhydrin]]<ref>{{cite press release | publisher = [[Dow Chemical Company]] | url = http://epoxy.dow.com/epoxy/news/2007/20070326b.htm | title = Dow Epoxy Advances Glycerine-To-Epichlorohydrin and Liquid Epoxy Resins Projects by Choosing Shanghai Site |date=26 March 2007}}</ref>, a raw material for [[epoxy resins]]. |
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*Glycerol may be used as antifreeze for plants, if mixed with water in a 10% solution. It is believed to be effective at temperatures near -18°C |
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*Glycerin may serve as a source of energy used in waste water treatment plant digesters |
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==Metabolism== |
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Glycerol is a precursor for synthesis of [[triacylglycerol]]s and of [[phospholipid]]s in the liver and [[adipose tissue]]. When the body uses stored fat as a source of energy, glycerol and [[fatty acid]]s are released into the bloodstream. The glycerol component can be converted to [[glucose]] by the [[liver]] and provides energy for cellular metabolism. |
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Before glycerol can enter the pathway of [[glycolysis]] or [[gluconeogenesis]] (depending on physiological conditions), it must be converted to their intermediate [[glyceraldehyde 3-phosphate]] in the following steps: |
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{|class="toccolours" border="0" style="font-size:90%" align="center" |
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|- |
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| bgcolor="lightgreen" align="center" | [[Glycerol]] |
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| bgcolor="pink" colspan="2" align="center" | [[Glycerol kinase]] |
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| bgcolor="lightgreen" align="center" | [[Glycerol-3-phosphate]] |
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| bgcolor="pink" colspan="2" align="center" | [[Glycerol-3-phosphate dehydrogenase]] |
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| bgcolor="lightgreen" align="center" | [[Dihydroxyacetone phosphate]] |
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| bgcolor="pink" colspan="2" align="center" | [[Triosephosphate isomerase]] |
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| bgcolor="lightgreen" align="center" | [[Glyceraldehyde 3-phosphate]] |
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|- |
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| rowspan="3" align="center" | [[Image:Glycerin_Skelett.svg|100px]] |
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| valign="bottom" align="center" | ATP |
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| valign="bottom" align="center" | ADP |
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| rowspan="3" align="center" | [[Image:Glycerol-3-phosphate.png|100px]] |
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| valign="bottom" align="center" | NAD<sup>+</sup> |
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| valign="bottom" align="center" | NADH<br /> |
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| rowspan="3" align="center" | [[Image:DHAP.png|125px]] |
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| |
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| |
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| rowspan="2" align="center" | [[Image:G3P-2D-skeletal.png|150px]] |
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|- |
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| colspan="2" align="center" | [[Image:biochem reaction arrow foward YYNN horiz med.svg|60px]] |
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| colspan="2" align="center" | [[Image:biochem reaction arrow reversible YYYY horiz med.svg|60px]] |
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| colspan="2" align="center" | [[Image:GG-Pfeil 1.svg|60px]] |
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|- |
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| valign="top" | |
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| valign="top" | |
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| valign="top" align="center" | NAD<sup>+</sup> |
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| valign="top" align="center" | NADH<br /> |
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| valign="top" | |
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| valign="top" | |
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| valign="top" | |
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|} |
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The enzyme [[glycerol kinase]] is present only in the liver. In adipose tissue, glycerol 3-phosphate is obtained from [[dihydroxyacetone phosphate]] (DHAP) with the enzyme [[glycerol-3-phosphate dehydrogenase]]. |
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== Historical cases of contamination with diethylene glycol == |
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On May 4, 2007, the US [[Food and Drug Administration]] advised all US makers of medicines to test all batches of glycerine for the toxic [[diethylene glycol]].<ref>U.S. Food and Drug Administration. [http://www.fda.gov/bbs/topics/NEWS/2007/NEW01628.html "FDA Advises Manufacturers to Test Glycerin for Possible Contamination."] Released May 4, 2007. Last retrieved May 8, 2007.</ref> This follows an occurrence of 100 fatal poisonings in [[Panama]] resulting from a Chinese factory deliberately falsifying records in order to export the cheaper diethylene glycol as the more expensive glycerol.<ref>WALT BOGDANICH and JAKE HOOKER. [http://www.nytimes.com/2007/05/06/world/06poison.html "From China to Panama, a Trail of Poisoned Medicine."] New York Times. Published: May 6, 2007. Last retrieved May 8, 2007.</ref> Glycerine and diethylene glycol are similar in appearance, smell, and taste. The US [[Federal Food, Drug, and Cosmetic Act]] was passed following the 1937 "[[Elixir Sulfanilamide]]" incident of poisoning caused by diethylene glycol contamination of medicine. |
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==See also== |
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*[[Oleochemical]]s |
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*[[Nitroglycerin]] |
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==References== |
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*[http://www.health.gov/dietaryguidelines/dga2005/report/HTML/G1_Glossary.htm U.S. Health.gov dietary guidelines] |
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{{reflist|2}} |
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==External links== |
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{{wiktionary}} |
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*[http://www.biocheminfo.org/klotho/html/glycerol.html Glycerol on BioChemInfo.org] |
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*[http://journeytoforever.org/biofuel_library/Mariller.html Absolute alcohol using glycerol] |
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*[http://www.compchemwiki.org/index.php?title=Glycerol Computational Chemistry Wiki] |
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*[http://twt.mpei.ac.ru/MAS/Worksheets/PrGlycerol.mcd Physical Property of glycerol] |
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[[Category:Alcohols]] |
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[[Category:Polyols]] |
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[[Category:Food additives]] |
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[[Category:Household chemicals]] |
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[[Category:Cosmetic chemicals]] |
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[[Category:Alcohol solvents]] |
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[[Category:Laxatives]] |
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[[Category:Glassforming liquids and melts]] |
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{{Link FA|pt}} |
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[[ar:جليسرول]] |
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[[bg:Глицерин]] |
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[[ca:Glicerol]] |
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[[cs:Glycerol]] |
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[[da:Glycerin]] |
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[[de:Glycerin]] |
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[[et:Glütserool]] |
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[[el:Γλυκερίνη]] |
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[[es:Glicerol]] |
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[[eo:Glicerino]] |
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[[fr:Glycérol]] |
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[[gl:Glicerol]] |
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[[ko:글리세롤]] |
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[[hr:Glicerol]] |
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[[is:Glýseról]] |
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[[it:Glicerolo]] |
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[[he:גליצרול]] |
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[[lv:Glicerīns]] |
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[[lb:Glycerol]] |
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[[lt:Glicerolis]] |
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[[hu:Glicerin]] |
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[[nl:Glycerine]] |
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[[ja:グリセリン]] |
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[[no:Glyserol]] |
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[[nn:Glyserol]] |
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[[pl:Gliceryna]] |
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[[pt:Glicerol]] |
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[[ro:Glicerină]] |
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[[ru:Глицерин]] |
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[[sk:Glycerol]] |
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[[sl:Glicerol]] |
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[[su:Gliserol]] |
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[[fi:Glyseroli]] |
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[[sv:Propantriol]] |
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[[vi:Glyxêrin]] |
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[[tr:Gliserin]] |
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[[uk:Гліцерин]] |
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[[zh:丙三醇]] |
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