 | |
 | |
 | |
| Names | |
|---|---|
| Preferred IUPAC name Octadecanoic acid | |
Other names
| |
| Identifiers | |
| |
3D model (JSmol) | |
| 608585 | |
| ChEBI | |
| ChEMBL | |
| ChemSpider |
|
| DrugBank |
|
| ECHA InfoCard | 100.000.285 |
| EC Number |
|
| 11738 | |
| KEGG | |
| RTECS number |
|
| UNII | |
| |
| |
| Properties | |
| C18H36O2 | |
| Molar mass | 284.484 g·mol−1 |
| Appearance | White solid |
| Odor | Pungent, oily |
| Density | 0.9408 g/cm3 (20 °C)[2] 0.847 g/cm3 (70 °C) |
| Melting point | 69.3 °C (156.7 °F; 342.4 K)[2] |
| Boiling point | 361 °C (682 °F; 634 K) decomposes 232 °C (450 °F; 505 K) at 15 mmHg[2] |
| 0.0018 g/100 g (0 °C) 0.0029 g/100 g (20 °C) 0.0034 g/100 g (30 °C) 0.0042 g/100 g (45 °C) 0.0050 g/100 g (60 °C)[3] | |
| Solubility | Soluble in[4] |
| Solubility indichloromethane | 3.58 g/100 g (25 °C) 8.85 g/100 g (30 °C) 18.3 g/100 g (35 °C)[4] |
| Solubility inhexane | 0.5 g/100 g (20 °C) 4.3 g/100 g (30 °C) 19 g/100 g (40 °C) 79.2 g/100 g (50 °C) 303 g/100 g (60 °C)[4] |
| Solubility inethanol | 1.09 g/100 mL (10 °C) 2.25 g/100 g (20 °C) 5.42 g/100 g (30 °C) 22.7 g/100 g (40 °C) 105 g/100 g (50 °C) 400 g/100 g (60 °C)[3] |
| Solubility inacetone | 4.73 g/100 g[5] |
| Solubility inchloroform | 15.54 g/100 g[5] |
| Solubility intoluene | 13.61 g/100 g[5] |
| Vapor pressure | 0.01 kPa (158 °C)[2] 0.46 kPa (200 °C) 16.9 kPa (300 °C)[6] |
| −220.8·10−6 cm3/mol | |
| Thermal conductivity | 0.173 W/m·K (70 °C) 0.166 W/m·K (100 °C)[7] |
Refractive index (nD) | 1.4299 (80 °C)[2] |
| Structure | |
| B-form =Monoclinic[8] | |
| B-form = P21/a[8] | |
| B-form = Cs 2h[8] | |
a = 5.591 Å,b = 7.404 Å,c = 49.38 Å (B-form)[8] α = 90°, β = 117.37°, γ = 90° | |
| Thermochemistry | |
| 501.5 J/mol·K[2][6] | |
Std molar entropy(S⦵298) | 435.6 J/mol·K[2] |
Std enthalpy of formation(ΔfH⦵298) | −947.7 kJ/mol[2] |
Std enthalpy of combustion(ΔcH⦵298) | −11342.4 kJ/mol[9] |
| Hazards | |
| NFPA 704 (fire diamond) | |
| Flash point | 205 °C (401 °F; 478 K) |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | 4640 mg/kg (rats, oral)[10] 21.5 mg/kg (rats, intravenous)[4] |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Stearic acid (/ˈstɪərɪk/STEER-ik,/stiˈærɪk/stee-ARR-ik) is asaturated fatty acid with an 18-carbon chain.[9] TheIUPAC name isoctadecanoic acid.[9] It is a softwaxy solid with the formulaCH3(CH2)16COOH.[9] Thetriglyceride derived from three molecules of stearic acid is calledstearin.[9] Stearic acid is a prevalentfatty 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 69.4 °C (156.9 °F) °C and apKa of 4.50.[11]
Its name comes from theGreek word στέαρ "stéar", which meanstallow. Thesalts andesters of stearic acid are calledstearates.[9] As its glycerol ester, stearic acid is one of the most common saturated fatty acids found in nature and in the food supply, followingpalmitic acid.[12][13] Dietary sources of stearic acid include meat, poultry, fish, eggs, dairy products, and foods prepared with fats; beeftallow,lard,butterfat,cocoa butter, andshea butter are rich fat sources of stearic acid.[9][12]
In terms of its biosynthesis, stearic acid is produced frompalmitoyl-CoA, withmalonyl-CoA a two-carbon building block (after decarboxylation).
Stearic acid is obtained from fats and oils by thesaponification of the triglycerides using hot water (about 100 °C). The resulting mixture is then distilled.[14] Commercial stearic acid is often a mixture of stearic andpalmitic acids, although purified stearic acid is available. Commercially,oleic acid, as found inpalm andsoy, can behydrogenated to give stearic acid.
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.[9] 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 tostearyl alcohol, and esterification with a range of alcohols.[9] This is used in a large range of manufactures, from simple to complex electronic devices.[9]
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).[12] Stearic acid is more abundant in animal fat (up to 33% in beef liver[15]: 739 ) than in vegetable fat (typically less than 5%).[12] The important exceptions are the foodscocoa butter (34%) andshea butter, where the stearic acid content (as atriglyceride) is 28–45%.[9][15] Examples of the use of stearic acid in food manufacturing include baked goods, frozen dairy products,gelatins,puddings, hard candy, and nonalcoholic beverages.[9]
Stearic acid (E numberE570) is found in some foods.[9][16]
Stearic acid is mainly used in the production of detergents, soaps, and cosmetics such asshampoos andshaving cream products.[9] Stearate soap, such assodium stearate, could be made from stearic acid but instead are usually produced bysaponification of stearic acid-containing triglycerides.Esters of stearic acid withethylene glycol (glycol stearate andglycol distearate) are used to produce a pearly effect in shampoos, soaps, and other cosmetic products.[9]
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 is an important component ofgrease. The stearate salts of zinc, calcium, cadmium, and lead are used as heat stabilizers forPVC. Stearic acid is used along withcastor oil for preparing softeners in textile sizing. They are heated and mixed with caustic potash or caustic soda. Related salts are also commonly used asrelease agents, e.g. in the production of automobile tires. As an example, it can be used to makecastings from aplasterpiece mold orwaste mold, and to make a mold from ashellacked 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 ofcalcium stearate, which functions as a release agent.[17]
Stearic acid can be converted tozinc stearate, which is used as alubricant for playing cards (fanning powder) to ensure a smooth motion whenfanning. Stearic acid is a common lubricant duringinjection molding and pressing ofceramic powders.[18]
Being inexpensive, nontoxic, and fairly inert, stearic acid finds many niche applications.[9][14] 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.[9]
Stearic acid is used as a negative plate additive in the manufacture oflead-acid batteries.[citation needed] It is added at the rate of 0.6 g per kg of the oxide while preparing the paste. It is believed to enhance thehydrophobicity of the negative plate, particularly during dry-charging process. It also reduces the extension ofoxidation 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 ofcandle-making. Stearic acid is used along with simplesugar orcorn syrup as a hardener incandies.[9]
Anisotope labeling study in humans[19] concluded that the fraction of dietary stearic acid thatoxidatively desaturates tooleic acid is 2.4 times higher than the fraction ofpalmitic acid analogously converted topalmitoleic acid.Also, stearic acid is less likely to be incorporated intocholesterol esters.In epidemiologic and clinical studies, stearic acid was found to be associated with loweredLDLcholesterol in comparison with other saturated fatty acids.[12]
| Oil palms | |||||||
|---|---|---|---|---|---|---|---|
| Diseases and pests |
| ||||||
| Components | |||||||
| Processes | |||||||
| Products | |||||||
| Organisations |
| ||||||
| Policies, impacts and debates | |||||||
| By country | |||||||
| International | |
|---|---|
| National | |
| Other | |
