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glycerol

glycerol, glycerin, glycerine, or 1,2,3-propanetriol (prō´pāntrī´ŏl), CH2OHCHOHCH2OH, colorless, odorless, sweet-tasting, syrupy liquid. Glycerol is a trihydric alcohol. It melts at 17.8°C, boils with decomposition at 290°C, and is miscible with water and ethanol. It is hygroscopic; i.e., it absorbs water from the air; this property makes it valuable as a moistener in cosmetics. Glycerol is present in the form of its esters (glycerides) in all animal and vegetable fats and oils. It is obtained commercially as a byproduct when fats and oils are hydrolyzed to yield fatty acids or their metal salts (soaps). Glycerol is also synthesized on a commercial scale from propylene (obtained by cracking petroleum), since supplies of natural glycerol are inadequate. Glycerol can also be obtained during the fermentation of sugars if sodium bisulfite is added with the yeast. Glycerol is widely used as a solvent; as a sweetener; in the manufacture of dynamite, cosmetics, liquid soaps, candy, liqueurs, inks, and lubricants; to keep fabrics pliable; as a component of antifreeze mixtures; as a source of nutrients for fermentation cultures in the production of antibiotics; and in medicine. It has many other uses as well.

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glycerol

glycerol A trihydric alcohol, chemically 1,2,3‐propane triol (CH2OHCHOHCH2OH), also known as glycerine. Simple or neutral fats are esters of glycerol with three molecules of fatty acid, i.e. triacylglycerols, sometimes known as triglycerides. See also glycerides.

Glycerol is a colourless, odourless, viscous liquid, sweet to taste; it is made from fats by alkaline hydrolysis (saponification). Used as a solvent for flavours, as a humectant to keep foods moist, and in cake batters to improve texture and slow staling.

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glycerol

glycerol (glycerine; propane-1,2,3,-triol) A trihydric alcohol, HOCH2CH(OH)CH2OH. Glycerol is a colourless sweet-tasting viscous liquid, miscible with water but insoluble in ether. It is widely distributed in all living organisms as a constituent of the glycerides, which yield glycerol when hydrolysed. Glycerol itself is used as an antifreeze molecule by certain organisms.

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glycerol

glyc·er·ol / ˈglisəˌrôl; -ˌräl/ • n. a colorless, sweet, viscous liquid, CH2(OH)CH(OH)CH2(OH), formed as a by-product in soap manufacture. It is used as an emollient and laxative, and for making explosives and antifreeze.

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glycerol

glycerol (glycerine) Thick, syrupy, sweet liquid (1,2,3–trihydroxypropane, CH2OHCH(OH)CH2OH) obtained as a by-product of soap, and synthesized industrially from propene. It is used in the manufacture of various products, including paints, cosmetics, and explosives.

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glycerol

glycerol A three-carbon, linear, trihydroxy alcohol. Its fatty esters are a very important constituent of many lipids, and some of its phosphorylated derivatives are intermediates in glycolysis.

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glycerol

glycerol A 3-carbon, linear, trihydroxy alcohol. Its fatty esters are a very important constituent of many lipids, and some of its phosphorylated derivatives are intermediates in glycolysis.

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Glycerol

Glycerol

KEY TERMS

Resources

Glycerol is the common name of the organic compound whose chemical structure is HOCH2 CHOH CH2OH. Propane-1,2,3-triol or glycerin (USP), as it is also called, consists of a chain of three carbon atoms with each of the end carbon atoms bonded to two hydrogen atoms (CH) and a hydroxyl group (OH) and the central carbon atom is bonded to a hydrogen atom (CH) and a hydroxyl group (OH). Glycerol is a trihydric alcohol because it contains three hydroxyl or alcohol groups.

Glycerin is a thick liquid with a sweet taste that is found in fats and oils and is the primary triglyceride found in coconut and olive oil. It was discovered in 1779, when the Swedish chemist Carl Wilhelm Scheele (1742-1786) washed glycerol out of a heated a mixture of lead oxide (PbO) and olive oil. Today, it is obtained as a byproduct from the manufacture of soaps.

One important property of glycerol or glycerin is that is not poisonous to humans. Therefore it is used in foods, syrups, ointments, medicines, and cosmetics. Glycerol also has special chemical properties that allow it to be used where oil would fail. Glycerol is a thick syrup that is used as the body for many syrups, such as cough medicines and lotions used to treat ear infections. It is also an additive in vanilla extracts and other food flavorings.

Glycerin is added to ice cream to improve its texture, and its sweet taste decreases the amount of sugar needed. The base used in making toothpaste contains glycerin to maintain smoothness and shine. The cosmetic industry uses glycerin in skin conditioning lotions to replace lost moisture, relieve chapping, and keep skin soft. It is also added to shampoos to make them flow easily when poured from the bottle.

Raisins in cereals stay soft because they have been soaked in glycerol. Meat casings and food wrapping papers use glycerin to give them flexibility without brittleness. Similarly, tobacco is treated with this thick chemical to prevent the leaves from becoming brittle and crumbling during drying. It also adds sweetness to chewing tobacco.

Glycerol is added during the manufacture of soaps to prepare shiny transparent bars. Its trihydric alcohol structure makes it a useful chemical in the manufacture of various hard foams, like those that are placed under siding in buildings and around dish washers and refrigerators for insulation and sound proofing. Its chemical structure also makes it an excellent catalyst in the microbiological production of vinegar from alcohol.

In the manufacture of foods, drugs, and cosmetics, oil cannot be used as a lubricant because it might come in contact with the products and contaminate them. Therefore, the nontoxic glycerol is used to reduce friction in pumps and bearings. Gasoline and other hydrocarbon chemicals dissolve oil-based greases, so glycerin is used in pumps for transferring these fluids. Glycerol is also applied to cork gaskets to keep them flexible and tough when exposed to oils and greases as in automobile engines.

Glycerin is used as a lubricant in various operations in the textile industry, and can be mixed with sugar to make a nondrying oil. Glycerol does not turn into a solid until it is cooled to a very low temperature. This property is utilized to increase the storage life of blood. When small amounts of glycerin are added to red blood cells, they can be frozen for up to three years.

Chemical derivatives of glycerol or propane-1,2,3-triol are important in a wide range of applications. Nitroglycerin is the trinitrate derivative of glycerol, the key ingredient in the manufacture of dynamite explosives. Nitroglycerin can also be used in conjunction with gun cotton or nitrocellulose as a propellant in military applications. In the pharmaceutical industry, nitroglycerin relieves chest pains and in the treatment of various heart ailments. Another derivative, guaiacol glyceryl ether, is an ingredient in cough medicines, and glycerol methacry-late is used in the manufacture of soft contact lenses to make them permeable to air.

Glycerol esters are utilized in cakes, breads, and other bakery products as lubricants and softening agents. They also have similar applications in the making of candies, butter, and whipped toppings. A

KEY TERMS

Acetins Derivatives of glycerol prepared by heating glycerol with acetic acid.

specially designed glycerol ester called caprenin can be used as a low calorie replacement for cocoa butter.

The acetins are derivatives of glycerol that are prepared by heating glycerol with acetic acid. Monoacetin is used in the manufacture of dynamite, in tanning leather, and as a solvent for various dyes. Diacetin, another derivative of glycerol, is used as a solvent and a softening agent. Triacetin, the most useful of the acetins, is used in the manufacture of cigarette filters and as a component in solid rocket fuels. It is also used as a solvent in the production of photographic films, and has some utility in the perfume industry. Triacetin is added to dried egg whites so that they can be whipped into meringues.

See also Fat.

Resources

BOOKS

Carey, Francis A. Organic Chemistry. New York: McGraw-Hill, 2002.

Newman, A.A. Glycerol. Cleveland: C.R.C. Press, 1968.

OTHER

Pioneer Thinking. What Is Glycerin? <http://www.pioneerthinking.com/glycerin.html> (accessed November 25, 2006).

Andrew Poss

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Glycerol

Glycerol

Glycerol is the common name of the organic compound whose chemical structure is HOCH2-CHOHCH2OH. Propane-1,2,3-triol or glycerin (USP), as it is also called, consists of a chain of three carbon atoms with each of the end carbon atoms bonded to two hydrogen atoms (C-H) and a hydroxyl group (-OH) and the central carbon atom is bonded to a hydrogen atom (C-H) and a hydroxyl group (-OH). Glycerol is a trihydric alcohol because it contains three hydroxyl or alcohol groups. Glycerin is a thick liquid with a sweet taste that is found in fats and oils and is the primary triglyceride found in coconut and olive oil. It was discovered in 1779, when the Swedish chemist Carl Wilhelm Scheele (1742-1786) washed glycerol out of a heated a mixture of lead oxide (PbO) and olive oil. Today, it is obtained as a byproduct from the manufacture of soaps.

One important property of glycerol or glycerin is that is not poisonous to humans. Therefore it is used in foods, syrups, ointments, medicines, and cosmetics. Glycerol also has special chemical properties that allow it to be used where oil would fail. Glycerol is a thick syrup that is used as the "body" to many syrups, for example, cough medicines and lotions used to treat ear infections. It is also an additive in vanilla extracts and other food flavorings. Glycerin is added to ice cream to improve the texture, and its sweet taste decreases the amount of sugar needed. The base used in making toothpaste contains glycerin to maintain smoothness and shine. The cosmetic industry employs glycerin in skin conditioning lotions to replace lost skin moisture, relieve chapping, and keep skin soft. It is also added in hair shampoos to make them flow easily when poured from the bottle. The raisins found in cereals remain soft because they have been soaked in glycerol. Meat casings and food wrapping papers use glycerin to give them flexibility without brittleness. Similarly, tobacco is treated with this thick chemical to prevent the leaves from becoming brittle and crumbling during drying. It also adds sweetness to chewing tobacco. Glycerol is added during the manufacture of soaps in order to prepare shiny transparent bars. The trihydric alcohol structure of glycerin makes it a useful chemical in the manufacture of various hard foams, like those that are placed under siding in buildings and around dish washers and refrigerators for insulation and sound proofing. Analogously, the chemical structure of glycerol makes it an excellent catalyst in the microbiological production of vinegar from alcohol.

In the manufacture of foods, drugs, and cosmetics, oil cannot be employed as a lubricant because it might come in contact with the products and contaminate them. Therefore, the nontoxic glycerol is used to reduce friction in pumps and bearings. Gasoline and other hydrocarbon chemicals dissolve oil-based greases, so glycerin is used in pumps for transferring these fluids. Glycerol is also applied to cork gaskets to keep them flexible and tough when exposed to oils and greases as in automobile engines. Glycerin is used as a lubricant in various operations in the textile industry, and can be mixed with sugar to make a nondrying oil. Glycerol does not turn into a solid until it is cooled to a very low temperature . This property is utilized to increase the storage life of blood . When small amounts of glycerin are added to red blood cells, they can be frozen and maintained for up to three years.

Chemical derivatives of glycerol or propane-1,2,3-triol are important in a wide range of applications. Nitroglycerin is the trinitrate derivative of glycerol. One application of this chemical is as the key ingredient in the manufacture of dynamite explosives . Nitroglycerin can also be used in conjunction with gun cotton or nitrocellulose as a propellant in military applications. In the pharmaceutical industry, nitroglycerin is considered a drug to relieve chest pains and in the treatment of various heart ailments. Another derivative, guaiacol glyceryl ether , is an ingredient in cough medicines, and glycerol methacrylate is used in the manufacture of soft contact lenses to make them permeable to air. Glycerol esters are utilized in cakes, breads, and other bakery products as lubricants and softening agents. They also have similar applications in the making of candies, butter, and whipped toppings. A specially designed glycerol ester called caprenin can be used as a low calorie replacement for cocoa butter.

The acetins are derivatives of glycerol that are prepared by heating glycerol with acetic acid . Monoacetin is used in the manufacture of dynamite, in tanning leather, and as a solvent for various dyes. Diacetin, another derivative of glycerol, is used as a solvent and a softening agent. Triacetin, the most useful of the acetins, is used in the manufacture of cigarette filters and as a component in solid rocket fuels. It is also used as a solvent in the production of photographic films, and has some utility in the perfume industry. Triacetin is added to dried egg whites so that they can be whipped into meringues.

See also Fat.


Resources

books

Carey, Francis A. Organic Chemistry. New York: McGraw-Hill, 2002.

Newman, A.A. Glycerol. Cleveland: C.R.C. Press, 1968.


Andrew Poss

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Glycerol

Glycerol

OVERVIEW

Glycerol (GLIH-ser-ol) is a clear, colorless, odorless, sweet-tasting syrupy liquid. It is a trihydric alcohol, meaning that its molecules contain three hydroxyl (−OH) groups. Glycerol occurs naturally in all animal and plant cells. Glycerol was discovered in 1779 by the German chemist Karl Wilhelm Scheele (1742–1786) and named by the French chemist Michel Eugéne Chevreul (1786–1889) because of its sweet taste (glycos means "sweet" in Greek). In 1836 the French chemist Théophile-Jules Pelouze (1807–1867) determined the molecular formula for glycerol, and three decades later, in 1872, the compound was first synthesized (created in a laboratory) by the French chemist Charles Friedel (1832–1899). About 250 million kilograms (500 million pounds) of glycerol are produced in the United States each year, the majority of which goes to the production of food and personal care products.

KEY FACTS

OTHER NAMES:

Glycerin; glycerine; glycyl alcohol

FORMULA:

CH2OHCHOHCH2OH

ELEMENTS:

Carbon, hydrogen, oxygen

COMPOUND TYPE:

Trihydric alcohol (organic)

STATE:

Liquid

MOLECULAR WEIGHT:

92.09 g/mol

MELTING POINT:

18.1°C (64.6°F)

BOILING POINT:

290°C (554°F)

SOLUBILITY:

Miscible with water and alcohol; insoluble in ether, benzene, and chloroform

HOW IT IS MADE

The traditional method of making glycerol is by the saponification of fats. Fats are the esters of glycerol and one or more alcohols. When a fat is hydrolyzed in the presence of a catalyst, it is converted into the glycerol and alcohols from which it was originally made. This type of hydrolysis is called saponification because it is the usual method by which soaps (the Latin word for "soap" is sapon). Glycerol can be obtained, then, as a byproduct in the manufacture of soaps.

A number of synthetic methods for making glycerol are also available. Most of these procedures begin with propylene (propene; CH2=CHCH3) and chlorine and involve a series of steps that convert the three-carbon propylene to the three-carbon glycerol. Glycerol can also be obtained by treating simple sugars with hydrogen over a nickel catalyst. In the United States, about 80 percent of all glycerol produced is obtained by saponification methods, and the remaining 20 percent is made by synthetic methods.

COMMON USES AND POTENTIAL HAZARDS

The most common use for glycerol in the United States is in food products, where it acts as a sweetener and as a thickener in many foods. For example, it is added to ice cream to improve texture and to candy products and baked goods to increase the sweetness of the product. It is also used to make the flexible coatings on cheeses, sausages, and other meat products. About one-quarter of all glycerol made in the United States is used in the food products industry.

Nearly the same amount of glycerol is used in the preparation of personal care products, such as skin, hair, and soap products (23 percent) and in oral hygiene products, such as toothpastes and mouthwashes (17 percent). Some of the products that include glycerol are moisturizers, detergents, soaps, hair coloring agents, mascara, nail polish, nail polish removers, perfumes, body lotions, hair sprays, shaving creams, lipsticks, cough medicines, shampoos, and hair conditioners. Glycerol is also used as a humectant in tobaccos. A humectant is a material that helps a product conserve moisture and prevent it from drying out.

Interesting Facts

  • As winter approaches, many insects begin to produce glycerol to replace the water in their body tissues. Glycerol acts as an antifreeze to prevent the insects from freezing during the coldest part of the year.

Other uses for glycerol include:

  • In the manufacturer of explosives;
  • In the production of a variety of plastics and polymers, such as polyether polyols, urethanes, and alkyd resins;
  • As a lubricant in pumps, bearings, gaskets, and other mechanical systems;
  • In the manufacture of ink rolls, inks, and rubber stamps;
  • As an emulsifying agent, a material that helps two liquids that are not soluble in each other to stay mixed;
  • As an antifreeze; and
  • In a number of medical applications, such as the treatment of glaucoma and stroke.

Glycerol poses some safety problems because it is combustible and explosive under certain conditions. It presents no health hazards under normal circumstances of use, however.

Words to Know

ESTER
An organic compound formed in the reaction between an organic acid and an alcohol.
HYDROLYSIS
The process by which a compound reacts with water to form two new compounds.
MISCIBLE
able to be mixed; especially applies to the mixing of one liquid with another.
SYNTHESIS
A chemical reaction in which some desired chemical product is made from simple beginning chemicals, or reactants.

FOR FURTHER INFORMATION

"Glycerol." International Chemical Safety Cards. http://www.healthy-communications.com/msdsglycerin1.html (accessed on October 10, 2005).

"Glycerol." PDRhealth. http://www.pdrhealth.com/drug_info/nmdrugprofiles/nutsupdrugs/gly_0304.shtml (accessed on October 10, 2005).

Legwold, Gary. "Hydration Breakthrough." Bicycling (July 1994): 72-73.

"Material Safety Data Sheet: Glycerine." Department of Chemistry, Iowa State University. http://avogadro.chem.iastate.edu/MSDS/glycerine.htm (accessed on October 10, 2005).

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Glycerol

Glycerol

Glycerol, also known as glycerin, or glycerine, is a hygroscopic (water-absorbent) fluid. In its pure form, it is a sweet-tasting, colorless, odorless, and viscous liquid that is 100% soluble in water. Simply put, glycerol is a combination of sugar and alcohol; glycerol is the term used whenever the biological qualities of this compound are discussed.

Glycerol, either in a freestanding state or as a derivative compound, is an important feature in a number of important chemical functions within the body. The first of these is glycolysis, the process by which the carbohydrate product glucose is converted to a usable energy form. Glycolysis is a Greek word, a combined meaning "sweet" and "splitting," which neatly summarizes how the glucose molecule is reduced for the purpose of fuel production of adenosine triphosphate (ATP). Glycerol, in the form of glycerates, is created in this process.

Glycerol is also an important component of triglycerides, the storage form of fats that are ingested into the body as food. These compounds take their name from the fact the glycerol binds three fatty acids together into one compound for storage. Triglycerides are stored in adipose tissues, chiefly located at the abdomen and the buttocks. Glycerol is commonly referred to as the backbone provided to the fatty acids that are the largest component of the fats when they are stored in their triglyceride form. Glycerol and fatty acids are released through the breakdown of fats through the process of lipolysis. Adipose tissues are those specially constructed in the body to accommodate stores of fat for future energy use. When the adipose tissues are triggered to release their fat stores, the triglycerides are reduced to their two constituent parts, fatty acids and glycerol. The fatty acids are directed into the bloodstream for transport to a desired muscle for conversion into energy; the glycerol is transported to the liver where it is reformulated into glucose, and ultimately redirected for energy creation.

In its state as found outside of the body, glycerol has many uses. It is approximately 60% as sweet as granular table sugar and is consequently used as a food and beverage sweetener. Glycerol and its derivatives are also used as humectants, substances that will keep materials moist (as glycerol is a powerful water-absorbing agent). Glycerol also has a number of uses as a lubricant.

Glycerol has been the subject of considerable sports science review. The main research focus has centered on the question of whether the ability of glycerol, if added to the water or other fluids consumed by endurance athletes as part of their competition hydration strategy, would assist in the creation of a hyper-hydration state, in which the effect of a particular quantity of fluid consumed in hot or humid conditions would be increased. In theory, the consumption of glycerol with fluid will increase the effective concentration of the water, known as the osmolarity, in the blood and the tissue of the athlete. This increased osmolarity would remain until the glycerol was removed from the bloodstream by the kidneys and broken down by the body. The simple ingestion of large volumes of water will also increase osmolarity, but only in the short term; the body will quickly begin to produce greater corresponding amounts of urine to offset the osmolarity effect. Numerous scientific studies had been conducted employing varying amounts of glycerol in relation to fluids, with inconclusive results. The bulk of these studies were conducted using exercise samples that were of moderate intensity, approximately 50% of the subject's VO2 max.

At the 2004 Athens Olympics, American marathoner Deena Kastor won a bronze medal in what was widely viewed as a very surprising result. In the hot weather conditions of that intense championship race, Kastor had hydrated herself with a glycerol solution. Further research has tended to confirm that in high-intensity endurance exercise scenarios, glycerol will promote greater hydration than water alone. Glycerol is broadly available as a supplement for the purpose of producing a hyper-hydration state; until 1997, glycerol was a prohibited substance in international athletics. Glycerol is now permitted for use by athletes by the World Anti-Doping Agency (WADA).

Glycerol, in the form of iodinated glycerol, is sometimes prescribed as an expectorant, a medication designed to loosen the phlegm and mucous of the lungs and the breathing passages in asthma or bronchitis sufferers. It has a number of side effects, particularly nausea, headaches, and stomach upset.

see also Fat intake; Liver function.

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