The stearic acid is a solid organic compound whose chemical formula is CH3(CHtwo)16COOH. It is a carboxylic acid that belongs to the group of long chain saturated fatty acids. It is yellowish-white in color and has an odor similar to that of tallow or animal fat..
It is called a fatty acid because it is present in many animal and vegetable fats and oils. It is part of the metabolism of most living beings and is generally found in the form of glycerin ester.
Cocoa has a high proportion of it, as well as the tallow of bovine animals, pork fat and butter. It is also present in vegetable oils such as corn. To obtain it, tristearin is hydrolyzed, that is, it is treated with water and alkali..
The ingestion of stearic acid with food and its effect on health currently poses doubts for researchers. It seems to have more harmful than beneficial effects.
It is useful in the preparation of drugs, water-insulating packaging, paraffin candles, lubricating greases, materials for molding figures, cosmetics, ointments, creams, among many other applications..
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The stearic acid molecule has a straight chain of 18 carbon atoms in which the last carbon atom is part of a carboxylic group -COOH. The carbon chain has only single C-C bonds as it is a saturated fatty acid.
Its expanded formula is:
CH3-CHtwo-CHtwo-CHtwo-CHtwo-CHtwo-CHtwo-CHtwo-CHtwo-CHtwo-CHtwo-CHtwo-CHtwo-CHtwo-CHtwo-CHtwo-CHtwo-COOH
-Stearic acid
-Octadecanoic acid
-Stearic acid
White to slightly yellow, crystalline solid with a mild sebum-like odor.
284.5 g / mol
69.3 ºC
383 ºC
196 ºC (closed cup method).
0.9408 g / cm3 at 20 ºC
Insoluble in water and floats on top of it. Slightly soluble in alcohol. Soluble in ether, acetone and chloroform.
pKto = 4.75
Stearic acid reacts with sodium hydroxide (NaOH) to form sodium stearate which is a soap. Most soaps contain sodium stearate.
Stearic acid and sodium stearate are considered generally safe and non-toxic compounds..
Stearic acid is one of the constituents of many oils and fats of vegetable and animal origin. It is generally found in the form of its glycerin ester.
It is present in many solid fats such as tallow and to a lesser extent in semi-solid fats such as lard, butter and in vegetable oils such as corn and cotton..
It is an important component of cocoa butter (38%) and shea (African tree that produces a type of nuts) (38.1%).
It is part of the metabolism of many living things, such as plants, mammals, humans, crustaceans and algae. This means that, for example, humans can synthesize it in their body.
Stearic acid, although it occurs naturally in the human body, is also ingested with foods that contain it both from its source and added to its composition..
It should be noted that among industrially processed foods, fats have been discontinued trans for being very harmful to human health. These fats were replaced by saturated fatty acids, including stearic acid..
The effects of this substitution are still under study. In general, long-chain saturated fatty acids increase low-density cholesterol levels, which is related to mortality from coronary and heart disease.
However, some studies indicate that stearic acid reduces low-density cholesterol, which suggests that it has antiatherogenic properties, that is, that it does not generate plaque formation in the arteries, but rather favors the health of blood vessels..
On the other hand, other research indicates that it has the highest prothrombotic potential of long-chain saturated fatty acids, this means that it can promote blood vessel plugging events.
In addition, high levels of stearic acid in the blood have been found to be toxic to certain cells of the pancreas, which can aggravate the symptoms of type 2 diabetes. This disease is common in people who are very overweight..
It is for these reasons that its effects are still being investigated since it has not been possible to clarify whether its action is favorable or not to the health of the human organism.
It can be obtained by hydrolysis of glycerin stearate or tristearin C3H5(COOC17H35)3, according to the following chemical reaction:
Triestearin + Sodium hydroxide → Sodium stearate + Glycerin
To produce it commercially, the hydrogenation of 18-carbon unsaturated fatty acids is carried out, such as those contained in cotton seeds and other vegetables..
In other words, hydrogen is added to the C = C double bonds of unsaturated fatty acids, remaining as C-C single bonds, as follows:
-CH = CH- + Htwo → -CHtwo-CHtwo-
Stearic acid is an important commercial chemical compound.
It is used in the pharmaceutical industry for the manufacture of various medicines, such as suppositories, coated pills for intestinal conditions or to coat bitter remedies, among others. It is also an ingredient in ointments or ointments.
Because it is insoluble in water, it is used in the food industry for insulating packaging and in the preparation of various types of waterproof materials..
It is also used as an ingredient in jellies, puddings, candies and non-alcoholic beverages because it gives them a certain viscosity..
It is used in the manufacture of stearin candles and is added to paraffin wax in small quantities. Due to its texture, it is also used in mouldable materials that are used to make three-dimensional models..
Also works in coatings against static electricity.
Its sodium salt is a soap and is also used to harden soaps. Because it is a harmless compound for humans, it is used to make cosmetics, as an emollient or a fatliquor for creams. Also serves to soften plastics.
Stearic acid is used to prepare other chemical compounds such as certain metallic stearates, for example aluminum, which is used to make lubricating greases by thickening the oils that make them up..
In addition, it is an ingredient in some pesticides, it is used in varnish dryers and as a vulcanization activator for synthetic rubber..
Stearic acid has been used successfully in ultraviolet (UV) light traps to attract dengue-transmitting mosquitoes.
Its characteristic odor is similar to that of lactic acid, which is the one found in the skin of human beings, so when placed in the traps it attracts mosquitoes, which are trapped in the device and die..
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