Glycerol
From Free net encyclopedia
| Glycerol | |
|---|---|
| Chemical name | 1,2,3-propanetriol |
| Chemical formula | C3H8O3 |
| Molecular mass | 92.09 g/mol |
| Melting point | 18°C |
| Boiling point | 290 °C |
| Density | 1.261 g/cm3 |
| Food energy | 4.32 kcal/g |
| CAS number | 56-81-5 |
| HS number | Crude Glycerol:1520.00.00 Pure Glycerol:2905.45.00 |
| SMILES | OCC(O)CO |
| Image:Glycerine chemical structure.png | |
Glycerol, also well known as glycerin and glycerine, and less commonly as propane-1,2,3-triol, 1,2,3-propanetriol, 1,2,3-trihydroxypropane, glyceritol, and glycyl alcohol is a colorless, odorless, hygroscopic, and sweet-tasting viscous liquid. Glycerin is a sugar alcohol and has three hydrophilic alcoholic hydroxyl groups (-OH) that are responsible for its solubility in water. Glycerin is prochiral. Glycerin is used in glycerin soap, in cosmetics and creams, in foods, in chemistry, and in glycerin fog machine mist. Glycerin is produced from dihydroxyacetone phosphate (DHAP) by the enzyme glycerol three-phosphate dehydrogenase (Gpd p) in the mitochondrion of the eukaryotic cell during glycolysis.[1]
Contents |
Glycerin and triglycerides
Image:Glycerol-3DModel.png When referring to its function in living organisms, the term glycerol is preferred. Glycerol is an important component of triglycerides (i.e. fats and oils) and of phospholipids. Glycerol is a three-carbon substance that forms the backbone of fatty acids in fats.(1) 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.
A byproduct of saponification and transesterification to obtain biodiesel, this is produced by hydrolysis of three ester linkages and loss of three equivalents of fatty acid from fat or biological oil.
Fats and oils are insoluble in water, because the OH groups of glycerin are replaced by ester groups. They are hydrophobic.
Glycerin and biodiesel
As a byproduct of biodiesel production, each of the OH sites in HO-CH2-CH(-OH)-CH2-OH is one of the three places where a fatty acid chain is broken off the triglyceride molecule.
See: transesterification.
Purification
Like biodiesel by-product, the purification of the lower glycerin phase involves: neutralisation, separation of unreacted methanol, dilution with wash liquid stream coming from methylester washing, splitting of soaps and final concentration up to 80%. Partially refined glycerin can be delivered as such to specialized distillers.
Feedstock pre-treatment and upgrading of glycerin to pharmaceutical grade (>99.7%) can be optionally implemented within the biodiesel factory itself.
When used in food, care should be taken to use only pure vegetable glycerin that is specifically labeled for use in food. "External use only" warnings should be heeded.
Applications
Drugs
- 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.
- Laxative suppositories, cough syrups, elixirs and expectorants.
Personal care
- Serves as an emollient, humectant, solvent and lubricant in personal care products
- Competes with sorbitol although glycerin has better taste and higher solubility.
- Toothpaste, mouthwashes, skin care products, hair care products and soaps
- Glycerin is a component of glycerin soap, which is made from denatured alcohol, glycerin, 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 moisturizing properties.
When used as an emollient, glycerin should never be applied undiluted to the skin. 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 glycerin is too concentrated. A minimum of two or three parts water should be added to one part glycerin.
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).
Glycerin has approximately 27 food 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. Glycerin should not be consumed undiluted, as unhydrated glycerin will draw water from tissues, causing blistering in the mouth and gastric distress. As food additive, glycerin (glycerol) is also known as E number E422.
Polyether polyols
- One of the major raw materials for the manufacture of polyols for flexible foams, and to a lesser extent rigid polyurethane foams
- Glycerin 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 glycerin.
Other applications
- Manufacture of paper as a plasticizer, Nitroglycerin, humectant and lubricant
- Humectant for pet foods to retain moisture and enhance palatability
- 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 glycerin (i.e., alkyl glyceryl ethers) instead of quaternary ammonium compounds.
- A way to preserve leaves is to submerge them in a solution of glycerin and water.
- Use a mixture of one part glycerin 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.
- 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.
- Use as antifreeze 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
See also: oleochemicals.
External links
Sources
Glycerine is also the title of a single (albeit mispronounced) from the album Sixteen Stone by the band Bush.cs:Glycerol da:Glycerin de:Glycerin es:Glicerol eo:Glicerino fr:Glycérol is:Glýseról it:Glicerolo he:גליצרול lv:Glicerīns lb:Glycerol nl:Glycerine ja:グリセリン pl:Gliceryna pt:Glicerina ru:Глицерин fi:Glyseroli sv:Propantriol zh:丙三醇