(Redirected from Glycerine)
| '' |
|---|
 Glycerol
 Ball-and-stick model of glycerol
 Space-filling model of glycerol |
| Chemical name | |
| Other names | glycerin
glycerine
propane-1,2,3-triol
1,2,3-propanetriol
1,2,3-trihydroxypropane
glyceritol
glycyl alcohol |
| Chemical formula | |
| Molecular mass | g/mol |
| CAS number | [http://www.nlm.nih.gov/cgi/mesh/2006/MB_cgi?term=56-81-5&rn=1 [56-81-5]] |
| HS number | Crude: 1520.00.00
Pure: 2905.45.00 |
| Density | g/cm³ |
| Viscosity | Pa.s |
| Melting point | °C (64.4°F) |
| Boiling point | °C (554°F) |
| Food energy | 4.32 kcal/g |
| SMILES | |
| Flash Point | 160 °C (closed cup) |
| Supplementary data page | |
|---|---|
| Structure & properties | ''n'', ''εr'', etc. |
| Thermodynamic data | Phase behavior
Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| |
'Glycerol' is a
chemical compound with the
formula HOCH
2CH(OH)CH
2OH. This colorless, odorless,
viscous liquid is widely used in pharmaceutical formulations. Also commonly called 'glycerin' or 'glycerine', it is a
sugar alcohol and fittingly is sweet-tasting and of low toxicity. Glycerol has three
hydrophilic alcoholic
hydroxyl groups that are responsible for its solubility in
water and its
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). It is a central component of
lipids.
Synthesis
Glycerol (3D model), showing the atoms and the lone electron pairs associated with the oxygen atoms (in pink)
Since glycerol forms the backbone of
triglycerides, it is produced on
saponification or
transesterification. Soap making and
biodiesel production are examples of the former and latter.
Until recently, synthetic glycerol was mainly manufactured at an industrial scale from
epichlorohydrin though this process is no longer economical. Glycerol is a 10% by-product of biodiesel manufacture (via the transesterification of vegetable oils). This has led to a glut of crude glycerol on the market. Although this crude glycerol (typically containing 20% water and residual esterification catalyst) can be refined to a purified form, a great deal of research is being conducted to try to make value-added molecules from glycerol, as an alternative to
incineration. One such programme to add value to this glut of glycerol is the UK-based initiative
The Glycerol Challenge. Some potential uses for glycerol include the following:
★ Hydrogen gas production
★
Glycerine acetate (potential fuel additive)
[1]
★ Compost additive
★ Citric acid production
★ Conversion to
propylene glycol[2][3].
★ Conversion to
acrolein[4][5]
★ Conversion to
ethanol[6]
★ Conversion to
epichlorhydrin[7].
Epichlorhydrin is a raw material for
epoxy resins.
Metabolism
Glycerol is a precursor for synthesis of
triacylglycerols and of
phospholipids in the liver and adipose tissue. When the body uses stored fat as a source of energy, glycerol and
fatty acids are released into the bloodstream. The glycerol component can be converted to
glucose by the
liver and provides energy for cellular metabolism.
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:
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.
Applications
Medicine and pharmaceutical technology
★ Used in medical and pharmaceutical preparations, mainly as a means of improving smoothness, providing
lubrication and as a
humectant. Also may be used to lower intracranial and intraocular pressures.
★ Used at 10% to prevent tannins from precipitating in ethanol extracts of plants (
tinctures).
★ Used as a substitute for alcohol, as a solvent that will create a therapeutic herbal extraction, but 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.
[8][9][10]
★ Used as a
prochiral building block in
organic synthesis.
★ Used as a
laxative when introduced into the rectum in
suppository or liquid (
enema) form; irritates the bowel and induces a
hyperosmotic effect.
★
Cough syrups, elixirs and
expectorants.
Personal care
★ Serves as an
emollient,
humectant, solvent, and
lubricant in personal care products.
★ Competes with
sorbitol although glycerol has better taste and higher solubility.
★
Toothpaste,
mouthwashes,
skin care products, shaving cream,
hair care products and
soaps
★
★ Glycerol is a component of glycerol
soap, which is made from
denatured alcohol, glycerol, sodium castorate (from
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 properties. It is possible to make glycerol soap at home.
It was once believed that when used as an emollient, glycerol should never be applied undiluted to the skin. It was thought that the same powerful
hygroscopic property that draws moisture out of the air to moisten the skin will draw moisture out of the skin if the glycerol is too concentrated. This in fact has proven to be untrue.
Foods and beverages
★ Serves as
humectant, solvent and sweetener, may help preserve foods.
★ Solvent for flavors (such as
vanilla) and
food coloring.
★
Humectant and softening agent in
candy,
cakes and casings for
meats and
cheeses.
★ Manufacture of mono- and di-glycerides for use as
emulsifiers
★ Used in manufacture of polyglycerol
esters going into
shortenings and
margarine.
★ Used as filler in low-fat food products (i.e.,
cookies).
★ Used as
thickening agent in
liqueurs.
★ Produced when
butter becomes
rancid.
Glycerol 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. Glycerol should not be consumed undiluted, as unhydrated glycerol will draw water from tissues, causing blistering in the mouth and gastric distress. As food additive, glycerol is also known as
E number E422.
Feed
Glycerol is increasingly used in feeding animals.
Polyether polyols
★ One of the major raw materials for the manufacture of
polyols for flexible foams, and to a lesser extent rigid
polyurethane foams
★ Glycerol is the initiator to which propylene oxide/ethylene oxide is added
Alkyd resins (plastics) and cellophane
★ Used in surface coatings and paints
★ Used as a softener and plasticizer to impart flexibility, pliability and toughness
★ Uses include meat casings, collagen casings (medical applications)and nonmeat packaging
★ Plasticizer in
cellophane.
Absolute alcohol
★ There is an
absolute alcohol production process by dehydration using glycerol.
Other applications
★ Manufacture of paper as a
plasticizer,
Nitroglycerin, humectant and
lubricant. Nitroglycerin is an essential ingredient of smokeless gunpower 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 defense priorities in the days leading up to World War II.
★ Used in lubricating, sizing and softening of yarn and fabric
★ Used in de-/anti-icing fluids, as in
vitrification of blood cells for storage in
liquid nitrogen
★ Patent applications have been filed for detergent
softeners and
surfactants based on glycerol (i.e., alkyl glyceryl
ethers) instead of
quaternary ammonium compounds.
★ A way to preserve leaves is to submerge them in a solution of glycerol and water.
::Use a mixture of one part glycerol to two parts water. Place the mixture in a flat pan, and totally submerge the leaves in a single layer in the liquid. You'll have to weigh them down to keep them submerged. In two to six days, they should have absorbed the liquid and be soft and pliable. Remove them from the pan and wipe off all the liquid with a soft cloth. Done correctly, the leaves will remain soft and pliable indefinitely.
★ Often used in the preparation of lichen for use in model scenery and dioramas
★ Can be added to solutions of water and soap to increase that solution's ability to generate
soap bubbles that will last a long time.
★ Used as an antifreeze or a
cryoprotectant in
cryogenic process.
★ Used in
fog machine fluids
★ Used in
hookah tobacco mixtures (called "ma'assel" or "shisha" tobacco), often along with molasses and/or honey.
★ Counteracts
phenol burns
★ Now that biodiesel production likely will produce large quantities of co-product glycerine (about 0.1 lb of glycerine per lb of biodiesel), processes are being announced to manufacture
propylene glycol and
epichlorohydrin, traditionally
propylene derivatives, from glycerine.
★ A process has been announced to produce
ethanol through the metabolic action of
E. coli[11].
★ Used by some endurance athletes to counteract dehydration by "glycerol loading" before an event.
★ Used to preserve bacteria at -80 (prevents lysing of cells).
★ Used to increase the density of samples in
gel electrophoresis, making them settle in the wells more efficiently.
★ Used in
PCR as an additive. It decreases the
dielectric constant of the mixture, which will weaken
hydrogen bonds in the double-stranded
DNA and lower the annealing temperature.
★ When mixed with
potassium permanganate,
iron oxide, and
aluminum, it produces a spontaneous self igniting
hypergolic thermite reaction.
★ Used in the conservation of waterlogged organic objects (such as leather and wood) to stabilise before freeze-drying treatment.
★ Used in ink for desktop printers as a viscosity controller and stabilizer.
Danger of contamination with diethylene glycol
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.
[12] 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.
[13] 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.
See also
★
Oleochemicals
References
★
U.S. Health.gov dietary guidelines
1. http://pubs.acs.org/cgi-bin/asap.cgi/enfuem/asap/pdf/ef060647q.pdf
2. chemweek's Business Daily, Tuesday May 8, 2007
3. http://www.dow.com/propyleneglycol/news/20070315b.htm, accessed June 25, 2007
4. Ott, L. et al, "The catalytic dehydration of glycerol in sub- and supercritical water: a new chemical process for acrolein production" Green Chemistry VOl. 8 iss. 2 p. 214-220, 2006
5. Watanabe, M. et al, "Acrolein synthesis from glycerol in hot-compressed water." Bioresource technology 98 (2007) 1285-1290
6. http://www.sciencedaily.com/upi/index.php?feed=Science&article=UPI-1-20070625-13174400-bc-us-glycerin.xml
7. http://epoxy.dow.com/epoxy/news/2007/20070326b.htm, accessed June 25, 2007
8.
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
9. David Winston www.herbaltherapeutics.com
10. http://www.newhope.com/nutritionsciencenews/NSN_backs/Apr_99/backtalk.cfm
11. http://www.sciencedaily.com/releases/2007/06/070626115246.htm
12. U.S. Food and Drug Administration. "FDA Advises Manufacturers to Test Glycerin for Possible Contamination." Released May 4, 2007. Last retrieved May 8, 2007.
13. WALT BOGDANICH and JAKE HOOKER. "From China to Panama, a Trail of Poisoned Medicine." New York Times. Published: May 6, 2007. Last retrieved May 8, 2007.
External links
★
Glycerol on BioChemInfo.org
★
Absolute alcohol using glycerol
★
Computational Chemistry Wiki
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