Stearic acid ( , ) is a saturated

fatty acid In chemistry, in particular in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated and unsaturated compounds#Organic chemistry, saturated or unsaturated. Most naturally occurring fatty acids have an ...

with an 18-carbon chain. The

IUPAC name In chemical nomenclature, a preferred IUPAC name (PIN) is a unique name, assigned to a chemical substance and preferred among all possible names generated by IUPAC nomenclature. The "preferred IUPAC nomenclature" provides a set of rules for choos ...

is octadecanoic acid. It is a soft

wax Waxes are a diverse class of organic compounds that are lipophilic, malleable solids near ambient temperatures. They include higher alkanes and lipids, typically with melting points above about 40 °C (104 °F), melting to give lo ...

y solid with the formula . The

triglyceride A triglyceride (from '' tri-'' and '' glyceride''; also TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids. Triglycerides are the main constituents of body fat in humans and other vertebrates ...

derived from three molecules of stearic acid is called

stearin Stearin , or tristearin, or glyceryl tristearate is an odourless, white powder. It is a triglyceride derived from three units of stearic acid. Most triglycerides are derived from at least two and more commonly three different fatty acids. Like ...

. Stearic acid is a prevalent fatty-acid in nature, found in many animal and vegetable fats, but is usually higher in animal fat than vegetable fat. It has a melting point of °C and a

pKa In chemistry, an acid dissociation constant (also known as acidity constant, or acid-ionization constant; denoted ) is a quantitative measure of the strength of an acid in solution. It is the equilibrium constant for a chemical reaction :H ...

of 4.50. Its name comes from the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

word στέαρ "''stéar''", which means

tallow Tallow is a rendered form of beef or mutton suet, primarily made up of triglycerides. In industry, tallow is not strictly defined as beef or mutton suet. In this context, tallow is animal fat that conforms to certain technical criteria, inc ...

. The

salt In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...

s and

ester In chemistry, an ester is a compound derived from an acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds contain a distin ...

s of stearic acid are called stearates. As its ester, stearic acid is one of the most common saturated fatty acids found in nature and in the food supply, following

palmitic acid Palmitic acid (hexadecanoic acid in IUPAC nomenclature) is a fatty acid with a 16-carbon chain. It is the most common saturated fatty acid found in animals, plants and microorganisms.Gunstone, F. D., John L. Harwood, and Albert J. Dijkstra. The ...

.Gunstone, F. D., John L. Harwood, and Albert J. Dijkstra "The Lipid Handbook with Cd-Rom. 3rd ed. Boca Raton: CRC Press, 2007. , Dietary sources of stearic acid include meat, poultry, fish, eggs, dairy products, and foods prepared with fats; beef

lard Lard is a Quasi-solid, semi-solid white fat product obtained by rendering (animal products), rendering the adipose tissue, fatty tissue of a domestic pig, pig.

butterfat Butterfat or milkfat is the fatty portion of milk. Milk and cream are often sold according to the amount of butterfat they contain. Composition Butterfat is mainly composed of triglycerides. Each triglyceride contains three fatty acids. Butt ...

cocoa butter Cocoa butter, also called theobroma oil, is a pale-yellow, edible Vegetable oil, fat extracted from the cocoa bean (''Theobroma cacao''). It is used to make chocolate, as well as some ointments, toiletries, and pharmaceuticals. Cocoa butter h ...

, and

shea butter Shea butter ( , , or ; ) is a fat (triglyceride; mainly oleic acid and stearic acid) extracted from the nut of the African shea tree ('' Vitellaria paradoxa''). It is ivory in color when raw and commonly dyed yellow with borututu root or ...

are rich fat sources of stearic acid.

Production

In terms of its biosynthesis, stearic acid is produced from

palmitoyl-CoA Palmitoyl-CoA is an acyl-CoA thioester. It is an "activated" form of palmitic acid and can be transported into the mitochondrial matrix by the carnitine shuttle system (which transports fatty acyl-CoA molecules into the mitochondria), and once in ...

, with

malonyl-CoA Malonyl-CoA is a coenzyme A derivative of malonic acid. Biosynthesis Malonyl-CoA cannot cross membranes and there is no known malonyl-CoA import mechanism. The biosynthesis therefore takes place locally: * cytosol: Malonyl-CoA is formed by c ...

a two-carbon building block (after decarboxylation). Stearic acid is obtained from fats and oils by the

saponification Saponification is a process of cleaving esters into carboxylate salts and Alcohol (chemistry), alcohols by the action of aqueous alkali. Typically aqueous sodium hydroxide solutions are used. It is an important type of alkaline hydrolysis. When the ...

of the triglycerides using hot water (about 100 °C). The resulting mixture is then distilled. Commercial stearic acid is often a mixture of stearic and

s, although purified stearic acid is available. Commercially,

oleic acid Oleic acid is a fatty acid that occurs naturally in various animal and vegetable fats and oils. It is an odorless, colorless oil, although commercial samples may be yellowish due to the presence of impurities. In chemical terms, oleic acid is cl ...

, as found in

palm Palm most commonly refers to: * Palm of the hand, the central region of the front of the hand * Palm plants, of family Arecaceae ** List of Arecaceae genera **Palm oil * Several other plants known as "palm" Palm or Palms may also refer to: Music ...

and

soy The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume native to East Asia, widely grown for its edible bean. Soy is a staple crop, the world's most grown legume, and an important animal feed. Soy is a key source of f ...

, can be

hydrogenated Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organi ...

to give stearic acid.

Uses and occurrence

In general, the applications of stearic acid exploit its bifunctional character, with a polar head group that can be attached to metal cations and a nonpolar chain that confers solubility in organic solvents. The combination leads to uses as a surfactant and softening agent. Stearic acid undergoes the typical reactions of saturated carboxylic acids, a notable one being reduction to

stearyl alcohol Stearyl alcohol, or 1-octadecanol, is an organic compound classified as a saturated fatty alcohol with the formula CH3(CH2)16CH2OH. It takes the form of white granules or flakes, which are insoluble in water. It has a wide range of uses as an i ...

, and esterification with a range of alcohols. This is used in a large range of manufactures, from simple to complex electronic devices.

Food

Of the saturated fatty acids consumed in the United States, stearic acid consumption is second (26% of total saturated fatty acid intake) to palmitic acid (56% of total saturated fatty acid intake). Stearic acid is more abundant in animal fat (up to 33% in beef liver) than in vegetable fat (typically less than 5%). The important exceptions are the foods

(34%) and

, where the stearic acid content (as a

) is 28–45%. Examples of the use of stearic acid in food manufacturing include baked goods, frozen dairy products,

gelatin Gelatin or gelatine () is a translucent, colorless, flavorless food ingredient, commonly derived from collagen taken from animal body parts. It is brittle when dry and rubbery when moist. It may also be referred to as hydrolyzed collagen, coll ...

pudding Pudding is a type of food which can either be a dessert served after the main meal or a Savoury (dish), savoury (salty or sweet, and spicy) dish, served as part of the main meal. In the United States, ''pudding'' means a sweet, milk-based des ...

s, hard candy, and nonalcoholic beverages. Stearic acid (

E number E numbers, short for Europe numbers, are codes for substances used as food additives, including those found naturally in many foods, such as vitamin C, for use within the European Union (EU) and European Free Trade Association (EFTA). Commonly ...

''E570'') is found in some foods.

Soaps and cosmetics

Stearic acid is mainly used in the production of detergents, soaps, and cosmetics such as

shampoo Shampoo () is a hair care product, typically in the form of a viscous liquid, that is formulated to be used for cleaning (scalp) hair. Less commonly, it is available in solid bar format. (" Dry shampoo" is a separate product.) Shampoo is use ...

s and

shaving cream Shaving cream or shave cream is a category of cream cosmetics used for shaving preparation. The purpose of shaving cream is to soften the hair by providing lubrication. Different types of shaving creams include aerosol shaving cream (also kn ...

products. Stearate soap, such as

sodium stearate Sodium stearate (IUPAC: Sodium Octadecanoate) is the sodium salt of stearic acid. This white solid is the most common soap. It is found in many types of solid deodorants, rubbers, latex paints, and inks. It is also a component of some food additi ...

, could be made from stearic acid but instead are usually produced by

of stearic acid-containing triglycerides.

Ester In chemistry, an ester is a compound derived from an acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds contain a distin ...

s of stearic acid with

ethylene glycol Ethylene glycol ( IUPAC name: ethane-1,2-diol) is an organic compound (a vicinal diol) with the formula . It is mainly used for two purposes: as a raw material in the manufacture of polyester fibers and for antifreeze formulations. It is an odo ...

(

glycol stearate Glycol stearate (glycol monostearate or ethylene glycol monostearate) is an organic compound with the molecular formula C20H40O3. It is the ester of stearic acid and ethylene glycol. It is used as an ingredient in many types of personal care pr ...

and

glycol distearate Glycol distearate is the diester of stearic acid and ethylene glycol. It is mostly commonly encountered in personal care products and cosmetics where it is used to produce pearlescent effects as well as a moisturizer. Synthesis Glycol distearat ...

) are used to produce a pearly effect in shampoos, soaps, and other cosmetic products.

Lubricants, softening and release agents

In view of the soft texture of the sodium salt, which is the main component of soap, other salts are also useful for their lubricating properties.

Lithium stearate Lithium stearate is a chemical compound with the formula LiO2C(CH2)16CH3. It is formally classified as a soap (a salt of a fatty acid). Lithium stearate is a white soft solid, prepared by the reaction of lithium hydroxide and stearic acid. Lithiu ...

is an important component of grease. The stearate salts of zinc, calcium, cadmium, and lead are used as heat stabilizers for

PVC Polyvinyl chloride (alternatively: poly(vinyl chloride), colloquial: vinyl or polyvinyl; abbreviated: PVC) is the world's third-most widely produced synthetic polymer of plastic (after polyethylene and polypropylene). About 40 million tons o ...

. Stearic acid is used along with

castor oil Castor oil is a vegetable oil pressed from castor beans, the seeds of the plant ''Ricinus communis''. The seeds are 40 to 60 percent oil. It is a colourless or pale yellow liquid with a distinct taste and odor. Its boiling point is and its den ...

for preparing softeners in textile sizing. They are heated and mixed with caustic potash or caustic soda. Related salts are also commonly used as

release agent A release agent (also mold release agent, release coating, or mold release coating) is a chemical used to prevent other materials from bonding to surfaces. Release agents aid in processes involving mold release, die-cast release, plastic release ...

s, e.g. in the production of automobile tires. As an example, it can be used to make

casting Casting is a manufacturing process in which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a casting, which is ejected or ...

s from a

plaster Plaster is a building material used for the protective or decorative coating of walls and ceilings and for moulding and casting decorative elements. In English, "plaster" usually means a material used for the interiors of buildings, while "re ...

''piece mold'' or ''waste mold'', and to make a mold from a

shellac Shellac () is a resin secreted by the female Kerria lacca, lac bug on trees in the forests of India and Thailand. Chemically, it is mainly composed of aleuritic acid, jalaric acid, shellolic acid, and other natural waxes. It is processed and s ...

ked clay original. In this use, powdered stearic acid is mixed in water and the suspension is brushed onto the surface to be parted after casting. This reacts with the calcium in the plaster to form a thin layer of

calcium stearate Calcium stearate is a carboxylate salt of calcium, classified as a calcium soap. The salt is a component of some lubricants, surfactants, as well as many foodstuffs. It is a white waxy powder. Production and occurrence Calcium stearate is produc ...

, which functions as a release agent. Steric acid can be converted to

zinc stearate Zinc stearate is a "zinc soap" that is widely used industrially. In this context, soap is used in its formal sense, a metal salt of a fatty acid: in this case stearic acid. It is a white solid that repels water. It is insoluble in polar solvents s ...

, which is used as a

lubricant A lubricant (sometimes shortened to lube) is a substance that helps to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the function of transmitting forces, ...

for playing cards (

fanning powder Fanning may refer to: * Fanning (bees), a behaviour of worker bees signalling an entrance to a hive * Fanning (firearms), a shooting technique in which one hand holds a revolver and the other hits the hammer repeatedly * Fanning (surname) * Fannin ...

) to ensure a smooth motion when fanning. Stearic acid is a common lubricant during

injection molding Injection moulding (U.S. spelling: injection molding) is a manufacturing process for producing parts by injecting molten material into a mould, or mold. Injection moulding can be performed with a host of materials mainly including metals (for ...

and pressing of ceramic powders.

Niche uses

Being inexpensive, nontoxic, and fairly inert, stearic acid finds many niche applications. Varied examples of stearic acid use in manufacturing include soaps and greases, household soap products, synthetic rubber, cosmetic and pharmaceutical creams and lotions, candles, phonograph records, lubricants, shoe and metal polishes, food packaging, and rubber compounds. Stearic acid is used as a negative plate additive in the manufacture of lead-acid batteries. It is added at the rate of 0.6 g per kg of the oxide while preparing the paste. It is believed to enhance the

hydrophobic In chemistry, hydrophobicity is the chemical property of a molecule (called a hydrophobe) that is seemingly repelled from a mass of water. In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, thu ...

ity of the negative plate, particularly during dry-charging process. It also reduces the extension of

oxidation Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is ...

of the freshly formed lead (negative active material) when the plates are kept for drying in the open atmosphere after the process of tank formation. As a consequence, the charging time of a dry uncharged battery during initial filling and charging (IFC) is comparatively lower, as compared to a battery assembled with plates which do not contain stearic acid additive. Fatty acids are classic components of

candle A candle is an ignitable candle wick, wick embedded in wax, or another flammable solid substance such as tallow, that provides light, and in some cases, a Aroma compound, fragrance. A candle can also provide heat or a method of keeping time. ...

-making. Stearic acid is used along with simple

sugar Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose Glucose is a sugar with the Chemical formula#Molecular formula, molecul ...

corn syrup Corn syrup is a food syrup that is made from the starch of corn/maize and contains varying amounts of sugars: glucose, maltose and higher oligosaccharides, depending on the grade. Corn syrup is used in foods to soften Mouthfeel, texture, add vol ...

as a hardener in candies.

Metabolism

An isotope labeling study in humans concluded that the fraction of dietary stearic acid that oxidatively desaturates to

is 2.4 times higher than the fraction of

analogously converted to

palmitoleic acid Palmitoleic acid, or (9''Z'')-hexadec-9-enoic acid, is an omega-7 monounsaturated fatty acid (16:1n-7) with the formula CH3(CH2)5CH=CH(CH2)7COOH. It is a rare component of fats. It is a common constituent of the glycerides of human adipose tis ...

. Also, stearic acid is less likely to be incorporated into cholesterol esters. In epidemiologic and clinical studies, stearic acid was found to be associated with lowered

LDL Low-density lipoprotein (LDL) is one of the five major groups of lipoprotein that transport all fat molecules around the body in extracellular water. These groups, from least dense to most dense, are chylomicrons (aka ULDL by the overall densit ...

cholesterol Cholesterol is the principal sterol of all higher animals, distributed in body Tissue (biology), tissues, especially the brain and spinal cord, and in Animal fat, animal fats and oils. Cholesterol is biosynthesis, biosynthesized by all anima ...

in comparison with other saturated fatty acids.

Examples

;Salts *

Potassium stearate Potassium stearate is a metal-organic compound, a salt of potassium and stearic acid with the chemical formula . The compound is classified as a metallic soap, i.e. a metal derivative of a fatty acid. Synthesis Potassium stearate may be prepared b ...

Calcium stearate Calcium stearate is a carboxylate salt of calcium, classified as a calcium soap. The salt is a component of some lubricants, surfactants, as well as many foodstuffs. It is a white waxy powder. Production and occurrence Calcium stearate is produc ...

Cobaltous stearate Cobalt(II) stearate is a metal-organic compound, a salt of cobalt and stearic acid with the chemical formula . The compound is classified as a metallic soap, i.e. a metal derivative of a fatty acid. Synthesis An exchange reaction of sodium steara ...

Magnesium stearate Magnesium stearate is the chemical compound with the formula . It is a soap, consisting of salt containing two equivalents of stearate (the anion of stearic acid) and one magnesium cation (Mg2+). Magnesium stearate is a white, water-insoluble pow ...

* Mercuric stearate *

Sodium stearate Sodium stearate (IUPAC: Sodium Octadecanoate) is the sodium salt of stearic acid. This white solid is the most common soap. It is found in many types of solid deodorants, rubbers, latex paints, and inks. It is also a component of some food additi ...

Zinc stearate Zinc stearate is a "zinc soap" that is widely used industrially. In this context, soap is used in its formal sense, a metal salt of a fatty acid: in this case stearic acid. It is a white solid that repels water. It is insoluble in polar solvents s ...

;Esters * Estradiol stearate *

Glycol stearate Glycol stearate (glycol monostearate or ethylene glycol monostearate) is an organic compound with the molecular formula C20H40O3. It is the ester of stearic acid and ethylene glycol. It is used as an ingredient in many types of personal care pr ...

Stearin Stearin , or tristearin, or glyceryl tristearate is an odourless, white powder. It is a triglyceride derived from three units of stearic acid. Most triglycerides are derived from at least two and more commonly three different fatty acids. Like ...

Testosterone stearate Testosterone stearate, also known as testosterone octadecanoate, testosterone 17β-stearate, and androst-4-en-17β-ol-3-one 17β-stearate, is an injected anabolic-androgenic steroid (AAS) and an androgen ester – specifically, the C17β steara ...

References

External links

NIST Chemistry WebBook Entry
{{Authority control Fatty acids Stearates Alkanoic acids E-number additives