Jump to content

Stearic acid

From Wikipedia, the free encyclopedia
Stearic acid[1]
Skeletal formula of stearic acid
Ball-and-stick model of stearic acid
Stearic acid
Names
Preferred IUPAC name
Octadecanoic acid
Other names
Identifiers
3D model (JSmol)
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.000.285Edit this at Wikidata
EC Number
  • 200-313-4
KEGG
RTECS number
  • WI2800000
UNII
  • CCCCCCCCCCCCCCCCCC(=O)O
Properties
C18H36O2
Molar mass 284.484g·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]
0.00018 g/100 g (0 °C)
0.00029 g/100 g (20 °C)
0.00034 g/100 g (30 °C)
0.00042 g/100 g (45 °C)
0.00050 g/100 g (60 °C)[3]
Solubility Soluble in
[4]
Solubilityindichloromethane 3.58 g/100 g (25 °C)
8.85 g/100 g (30 °C)
18.3 g/100 g (35 °C)[4]
Solubilityinhexane 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]
Solubilityinethanol 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]
Solubilityinacetone 4.73 g/100 g[5]
Solubilityinchloroform 15.54 g/100 g[5]
Solubilityintoluene 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]
−220.8·10−6cm3/mol
Thermal conductivity 0.173 W/m·K (70 °C)
0.166 W/m·K (100 °C)[7]
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]
435.6 J/mol·K[2]
−947.7 kJ/mol[2]
−11342.4 kJ/mol[9]
Hazards
NFPA 704(fire diamond)
NFPA 704 four-colored diamondHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
1
0
Flash point 205 °C (401 °F; 478 K)
Lethal doseor concentration (LD, LC):
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 a saturatedfatty acidwith an 18-carbon chain.[9]TheIUPAC nameisoctadecanoic acid.[9]It is a softwaxysolid with the formulaCH3(CH2)16CO2H.[9]Thetriglyceridederived from three molecules of stearic acid is calledstearin.[9]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 69.4 °C (156.9 °F) °C and a pKa of 4.50.[11]

Its name comes from theGreekword στέαρ "stéar",which meanstallow.Thesaltsandestersof stearic acid are calledstearates.[9]As its 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 butterare rich fat sources of stearic acid.[9][12]

Production[edit]

In terms of its biosynthesis, stearic acid is produced frompalmitoyl-CoA,withmalonyl-CoAa two-carbon building block (after decarboxylation).

Stearic acid is obtained from fats and oils by thesaponificationof 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 inpalmandsoy,can behydrogenatedto give stearic acid.

Uses and occurrence[edit]

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]

Food[edit]

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]

Soaps and cosmetics[edit]

Stearic acid is mainly used in the production of detergents, soaps, and cosmetics such asshampoosandshaving creamproducts.[9]Stearate soap, such assodium stearate,could be made from stearic acid but instead are usually produced bysaponificationof stearic acid-containing triglycerides.Estersof stearic acid withethylene glycol(glycol stearateandglycol distearate) are used to produce a pearly effect in shampoos, soaps, and other cosmetic products.[9]

Lubricants, softening and release agents[edit]

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 stearateis an important component ofgrease.The stearate salts of zinc, calcium, cadmium, and lead are used as heat stabilisersPVC.Stearic acid is used along withcastor oilfor 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 makecastingsfrom aplasterpiece moldorwaste mold,and to make a mold from ashellackedclay 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]

Steric acid can be converted tozinc stearate,which is used as alubricantfor playing cards (fanning powder) to ensure a smooth motion whenfanning.Stearic acid is a common lubricant duringinjection moldingand pressing ofceramic powders.[18]

Niche uses[edit]

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 thehydrophobicityof the negative plate, particularly during dry-charging process. It also reduces the extension ofoxidationof 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 simplesugarorcorn syrupas a hardener incandies.[9]

Metabolism[edit]

Anisotope labelingstudy in humans[19]concluded that the fraction of dietary stearic acid thatoxidativelydesaturates tooleic acidis 2.4 times higher than the fraction ofpalmitic acidanalogously 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 loweredLDLcholesterolin comparison with other saturated fatty acids.[12]

Examples[edit]

Salts
Esters

References[edit]

  1. ^Susan Budavari, ed. (1989).Merck Index(11th ed.).Rahway, New Jersey:Merck & Co., Inc.p.8761.ISBN978-0-911910-28-5.
  2. ^abcdefghLide, David R., ed. (2009).CRC Handbook of Chemistry and Physics(90th ed.).Boca Raton, Florida:CRC Press.ISBN978-1-4200-9084-0.
  3. ^abRalston, A.W.; Hoerr, C.W. (1942). "The Solubilities of the Normal Saturated Fatty Acids".The Journal of Organic Chemistry.7(6): 546–555.doi:10.1021/jo01200a013.PMID20280727.
  4. ^abcd"stearic acid".Chemister.ru. 2007-03-19.Retrieved2017-06-30.
  5. ^abcSeidell, Atherton; Linke, William F. (1919).Solubilities of Inorganic and Organic Compounds(2nd ed.). D. Van Nostrand Company. p.677.
  6. ^abOctadecanoic acidin Linstrom, Peter J.; Mallard, William G. (eds.);NIST Chemistry WebBook,NIST Standard Reference Database Number 69,National Institute of Standards and Technology, Gaithersburg (MD) (retrieved 2014-06-15)
  7. ^Vargaftik, Natan B.; et al. (1993).Handbook of Thermal Conductivity of Liquids and Gases(illustrated ed.). CRC Press. p. 318.ISBN978-0-8493-9345-7.
  8. ^abcdvon Sydow, E. (1955). "On the structure of the crystal form B of stearic acid".Acta Crystallographica.8(9): 557–560.Bibcode:1955AcCry...8..557V.doi:10.1107/S0365110X55001746.
  9. ^abcdefghijklmnopqr"Stearic acid".PubChem, US National Library of Medicine. 29 April 2023.Retrieved5 May2023.
  10. ^Science Lab."Stearic acid MSDS"(PDF).Retrieved2020-09-30.
  11. ^Loften, J.R.; Linn, J.G.; Drackley, J.K.; Jenkins, T.C.; Soderholm, C.G.; Kertz, A.F. (August 2014)."Invited review: Palmitic and stearic acid metabolism in lactating dairy cows".Journal of Dairy Science.97(8): 4661–4674.doi:10.3168/jds.2014-7919.ISSN0022-0302.PMID24913651.
  12. ^abcdeHunter, J. E.; Zhang, J.; Kris-Etherton, P. M. (2009)."Cardiovascular disease risk of dietary stearic acid compared with trans, other saturated, and unsaturated fatty acids: A systematic review".American Journal of Clinical Nutrition.91(1): 46–63.doi:10.3945/ajcn.2009.27661.PMID19939984.
  13. ^Gunstone, F. D., John L. Harwood, and Albert J. Dijkstra "The Lipid Handbook with Cd-Rom. 3rd ed. Boca Raton: CRC Press, 2007.ISBN0849396883|ISBN978-0849396885
  14. ^abAnneken, David J.; Both, Sabine; Christoph, Ralf; Fieg, Georg; Steinberner, Udo; Westfechtel, Alfred (2006). "Fatty Acids".Ullmann's Encyclopedia of Industrial Chemistry.Weinheim: Wiley-VCH.doi:10.1002/14356007.a10_245.pub2.ISBN3527306730.
  15. ^abBeare-Rogers, J.; Dieffenbacher, A.; Holm, J.V. (2001)."Lexicon of lipid nutrition (IUPAC Technical Report)".Pure and Applied Chemistry.73(4): 685–744.doi:10.1351/pac200173040685.S2CID84492006.
  16. ^Aguilar, Fernando; Crebelli, Riccardo; Di Domenico, Alessandro; et al. (2017)."Re-evaluation of fatty acids (E 570) as a food additive".EFSA Journal.15(5): 4785.doi:10.2903/j.efsa.2017.4785.PMC7009963.PMID32625490.
  17. ^Angelo Nora; Alfred Szczepanek; Gunther Koenen (2005). "Metallic Soaps".Ullmann's Encyclopedia of Industrial Chemistry.Weinheim: Wiley-VCH.doi:10.1002/14356007.a16_361.ISBN978-3527306732.
  18. ^Tsenga, Wenjea J.; Mo Liua, Dean; Hsub, Chung-King (1999). "Influence of stearic acid on suspension structure and green microstructure of injection-molded zirconia ceramics".Ceramics International.25(2): 191–195.doi:10.1016/S0272-8842(98)00024-8.
  19. ^Emken, Edward A. (1994)."Metabolism of dietary stearic acid relative to other fatty acids in human subjects".American Journal of Clinical Nutrition.60(6): 1023S–1028S.doi:10.1093/ajcn/60.6.1023S.PMID7977144.

External links[edit]

Wikimedia Commons has media related toStearic acid.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Stearic_acid&oldid=1226537006"