How many hydroxyl groups does glycerine contain?

1,2,3 propanetriol
Glycerine occurs in the metabolism. It can be found in numerous fats and oils from animals and plants.
Effect on the human body

The odorless, sweet-tasting, difficult to move and hygroscopic (water-attracting) liquid is relatively harmless when swallowed up to a quantity of 50 milliliters. Larger amounts lead to a state of intoxication with headache and kidney pain. Contact with the undiluted liquid on the skin can cause slight irritation.

Chemical-physical properties

Due to its three hydroxyl groups (OH groups), glycerine belongs to the molecular structure trihydric alcohols. The glycerine molecule is strongly polar and therefore readily soluble in water. Below the melting point, anhydrous glycerine solidifies into crystals. The three OH groups enable good reactivity: glycerine initially reacts with dried potassium permanganate to form smoke. The resulting heat accelerates the exothermic reaction so much that a jet of flame strikes out. Various manganese compounds such as potassium manganate (VI), manganese (IV) oxide and manganese (III) oxide are formed as reaction products. The glycerine is oxidized to water and carbon dioxide.

Glycerine reacts with potassium permanganate.

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Glycerine can be oxidized, producing glyceraldehyde and dihydroxyacetone. Glyceric acid is obtained with nitric acid. However, if a nitrating acid made from fuming nitric acid and concentrated sulfuric acid is used, the hydroxyl groups esterify to form trisnitric acid glycerol ester. This ester is known under the name nitroglycerin, which is a highly explosive and impact-sensitive explosive. Manufacturing is also associated with great risks. The Swedish chemist and industrialist Alfred Nobel (1833-1896) developed a method for stabilizing nitroglycerin. If it is soaked up with kieselguhr it loses its impact-sensitive properties and it can only be detonated with a detonation fuse. Nobel got very rich with the invention of dynamite. However, the price was very high. Some workers and his own brother were killed in explosion accidents during production.

Low dose nitroglycerin is an important heart drug. It has a strong vasodilator effect and is taken in angina pectoris and the associated shortness of breath or in the event of an impending heart attack. The capsules shown contain 0.8 milligrams of nitroglycerin:

Glycerine forms numerous esters with acids. Fats, for example, consist of triglycerides, which are accessible through the esterification of all three hydroxyl groups of glycerine with carboxylic acids:

The discovery of glycerine is attributed to the Swedish chemist Carl Wilhelm Scheele (1742–1786). When the pigment black lead (lead (II) oxide) acted on olive oil, Scheele received a sweet-tasting, oily liquid, which he initially called "oil sweet". The role of glycerine in soap formation was elucidated in 1823 by the French chemist Michel-Eugène Chevreul (1786–1889). In the past, glycerine was obtained as a by-product in soap production. Today it is mainly made from propene, a product used in the cracking of long-chain alkanes. The propene is first converted to allyl chloride (CH2= CH-CH2Cl) chlorinated, which is then converted to glycerine in several intermediate steps. Another important process is the hydroxylation of allyl alcohol with hydrogen peroxide and a tungsten oxide catalyst.
Glycerine is required on a large scale for the production of plastics such as polyurethane foams and of dyes. It is contained in creams and ointments as a humectant. In the car it can be found in the brake fluid and in the antifreeze. It also serves as a plasticizer for films or as a water-absorbing additive for dye baths, copier inks, as well as for printing and stamping inks. Esterification with nitric acid produces nitroglycerin. This explosive is the basic component of dynamite.