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1,2,3-propanetriol(prō`pāntrī'ŏl), CH2OHCHOHCH2OH, colorless, odorless, sweet-tasting, syrupy liquid. Glycerol is a trihydric alcoholalcohol,
any of a class of organic compounds with the general formula R-OH, where R represents an alkyl group made up of carbon and hydrogen in various proportions and -OH represents one or more hydroxyl groups.
..... Click the link for more information. . 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 estersester,
any one of a group of organic compounds with general formula RCO2R′ (where R and R′ are alkyl groups or aryl groups) that are formed by the reaction between an alcohol and an acid.
..... Click the link for more information. (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 antibioticsantibiotic,
any of a variety of substances, usually obtained from microorganisms, that inhibit the growth of or destroy certain other microorganisms. Types of Antibiotics
..... Click the link for more information. ; and in medicine. It has many other uses as well.
(1,2,3-trihydroxypropane; 1,2,3-propanetriol), the simplest trihydric alcohol HOCH2—CHOH—CH2OH; a syrupy, colorless, nontoxic, sweet, odorless liquid. Melting point, 17.9° C; boiling point, 290° C; density, 1.26 g/cm3(25° C). Upon supercooling, it forms a glassy mass at about -100° C. Glycerol may be distilled without decomposition only under vacuum or with superheated steam. It is miscible with water in all proportions (the boiling point of aqueous glycerol solutions decreases with decreasing glycerol concentration; these solutions are characterized by low freezing points), as well as with methanol, ethanol, and acetone. It is soluble in mixtures of alcohol with ether or chloroform but is insoluble in fats, petroleum ether, benzene, and carbon disulfide. It dissolves many inorganic and organic materials, such as salts, alkalies, and sugars; it is hygroscopic and absorbs water from the air up to 40 percent (by weight). Glycerol forms mono-, di-, and tri-derivatives. Like other alcohols, it forms metallic derivatives—glycerates. On reacting with hydrogen halides or phosphorus halides, halohydrins are formed—for example, α-chlorohydrin, C1CH2CHOHCH2OH, and α, γ-dichloro-hydrin, ClCH2CHOHCH2Cl. Glycerol oxidizes to glyceraldehyde (CH2OH—CHOH—CH=O), dihydroxyacetone (CH2OH—CO—CH2OH), and glyceric acid (CH2OH— CHOH—COOH), as well as CO2 and water.
The dehydration of glycerol leads to the formation of polyglycerols or acrolein. Glycerol reacts with aldehydes and ketones to give the corresponding acetals and ketals (for example, acetaldehyde-glycerol acetal and acetone-glycerol ketal). Reaction with mineral acids gives esters—for example, the treatment of glycerol with a mixture of nitric and sulfuric acids yields glycerol trinitrate, so-called nitroglycerin. Acylation with organic acids, or with their derivatives gives mono-, di-, and triglycerides. The triglycerides of higher fatty acids comprise the main part of fats and oils of vegetable and animal origin.
Glycerol was first prepared by the saponification of natural fats (K. Scheele, 1779). It is produced mainly by synthetic methods based on propylene:
Other methods for the synthesis of glycerol are also known. Glycerol is used in the production of explosives and synthetic resins. Epichlorohydrin, which is produced from glycerol or from the intermediates in its synthesis, is the raw material for the production of epoxy resins. Glycerol is an important component of many food, cosmetic, and pharmaceutical products. It is used in the printing, leather, textile, and paper industries. Aqueous solutions of glycerol are used as antifreezes.
In medicine, glycerol is used locally as a skin softener, as well as in suppositories and enemas as a laxative. It serves as a base for the preparation of ointments and liniments. Glycerol derivatives, such as fats and lipids, play an important biological role.