View source for Stearic acid

{{short description|Eighteen-carbon straight-chain fatty acid}}
{{distinguish|Stearolic acid}}
{{chembox
| Name           = 
| Reference      = <ref>{{cite book|title = Merck Index|edition = 11th|page = [https://archive.org/details/merckindexency00buda/page/8761 8761]|publisher = [[Merck & Co.|Merck & Co., Inc]]|year = 1989|isbn = 978-0-911910-28-5|editor = Susan Budavari|location = [[Rahway, New Jersey]]|title-link = Merck Index}}</ref>
| ImageFile      = Stearic acid.svg
| ImageSize      = 240px
| ImageClass     = skin-invert
| ImageName      = Skeletal formula of stearic acid
| ImageFile1     = Stearic-acid-3D-balls.png
| ImageClass1 = bg-transparent  
| ImageSize1     = 240px
| ImageName1     = Ball-and-stick model of stearic acid
| ImageFile2     = Stearic acid crystallized.jpg
| ImageSize2     = 200px
| ImageName2     = Stearic acid
| PIN            = Octadecanoic acid <!-- Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book) -->
| SystematicName = 
| OtherNames     = {{Unbulleted list|C18:0 ([[lipid number]]s)}}
| IUPACName      = 
| Section1       = {{Chembox Identifiers
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 57-11-4
| Beilstein = 608585
| ChEBI = 28842
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 5091
| ChEMBL_Ref = {{ebicite|correct|EBI}}
| ChEMBL = 46403
| DrugBank_Ref = {{drugbankcite|correct|drugbank}}
| DrugBank = DB03193
| EINECS = 200-313-4
| Gmelin = 11738
| IUPHAR_ligand = 3377
| KEGG = C01530
| PubChem = 5281
| RTECS = WI2800000
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 4ELV7Z65AP
| StdInChI=1S/C18H36O2/c1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18(19)20/h2-17H2,1H3,(H,19,20)
| StdInChIKey = QIQXTHQIDYTFRH-UHFFFAOYSA-N
| SMILES = CCCCCCCCCCCCCCCCCC(=O)O
  }}
| Section2       = {{Chembox Properties
| C=18 | H=36 | O=2
| Appearance = White solid
| Odor = Pungent, oily
| Density = 0.9408 g/cm<sup>3</sup> (20 °C)<ref name=crc /><br> 0.847 g/cm<sup>3</sup> (70 °C)
| MeltingPtC = 69.3
| MeltingPt_ref = <ref name=crc />
| BoilingPtC = 361
| BoilingPt_notes = <br> decomposes<br> {{convert|232|C|F K}}<br> at 15 mmHg<ref name=crc />
| Solubility = 0.0018 g/100 g (0 °C)<br> 0.0029 g/100 g (20 °C)<br>0.0034 g/100 g (30 °C)<br> 0.0042 g/100 g (45 °C)<br> 0.0050 g/100 g (60 °C)<ref name="Ralston">{{cite journal|year = 2010|title = Supporting Information Solubility and Mass Transfer Coefficient Enhancement of Stearic Acid through Hydrotropy |journal = Journal of Chemical & Engineering Data|volume = 55|issue = 9|pages = 2980–2984|doi = 10.1021/je901041n|last1 = Theneshkumar|first1 = S.|last2 = Gnanaprakash|first2 = D.|first3 = Nagendra Gandhi|last3 = N.}}</ref>
| SolubleOther = Soluble in {{ubl|alkyl [[acetate]]s| [[alcohol (chemistry)|alcohol]]s|[[methyl formate]]|[[phenyl group|phenyl]]s|[[carbon disulfide]]|[[carbon tetrachloride]]}}<ref name=chemister>{{cite web|url=http://chemister.ru/Database/properties-en.php?dbid=1&id=4852 |title=stearic acid |publisher=Chemister.ru |date=2007-03-19 |access-date=2017-06-30}}</ref>
| Solubility1 = 3.58 g/100 g (25 °C)<br> 8.85 g/100 g (30 °C)<br> 18.3 g/100 g (35 °C)<ref name=chemister />
| Solvent1 = dichloromethane
| Solubility2 = 0.5 g/100 g (20 °C)<br> 4.3 g/100 g (30 °C)<br> 19 g/100 g (40 °C)<br> 79.2 g/100 g (50 °C)<br> 303 g/100 g (60 °C)<ref name=chemister />
| Solvent2 = hexane
| Solubility3 = 1.09 g/100 mL (10 °C)<br> 2.25 g/100 g (20 °C)<br> 5.42 g/100 g (30 °C)<br> 22.7 g/100 g (40 °C) <br>105 g/100 g (50 °C)<br> 400 g/100 g (60 °C)<ref name=Ralston />
| Solvent3 = ethanol
| Solubility4 = 4.73 g/100 g<ref name=sioc>{{cite book|last1 = Seidell|first1 = Atherton|last2 = Linke|first2 = William F.|year = 1919|title = Solubilities of Inorganic and Organic Compounds|url = https://archive.org/details/solubilitiesino01seidgoog|publisher = D. Van Nostrand Company|edition = 2nd|page = [https://archive.org/details/solubilitiesino01seidgoog/page/n702 677]}}</ref>
| Solvent4 = acetone
| Solubility5 = 15.54 g/100 g<ref name=sioc />
| Solvent5 = chloroform
| Solubility6 = 13.61 g/100 g<ref name=sioc />
| Solvent6 = toluene
| RefractIndex = 1.4299 (80 °C)<ref name=crc />
| VaporPressure = 0.01 kPa (158 °C)<ref name=crc /><br> 0.46 kPa (200 °C)<br> 16.9 kPa (300 °C)<ref name=nist>{{nist|name=Octadecanoic acid|id=C57114|accessdate=2014-06-15|mask=FFFF|units=SI}}</ref>
| ThermalConductivity = 0.173 W/m·K (70 °C) <br>0.166 W/m·K (100 °C)<ref>{{cite book|last = Vargaftik|first = Natan B.|year = 1993|title = Handbook of Thermal Conductivity of Liquids and Gases|publisher = CRC Press|edition = illustrated|isbn = 978-0-8493-9345-7|url = https://books.google.com/books?id=DFo1sZBwdNgC&pg=PA318|page = 318|display-authors=etal}}</ref>
| MagSus = −220.8·10<sup>−6</sup> cm<sup>3</sup>/mol
  }}
| Section3       = {{Chembox Structure
| CrystalStruct = B-form = [[monoclinic crystal system|Monoclinic]]<ref name=csba>{{cite journal | doi = 10.1107/S0365110X55001746| title = On the structure of the crystal form B of stearic acid| journal = Acta Crystallographica| volume = 8| issue = 9| pages = 557–560| year = 1955| last1 = von Sydow| first1 = E.| bibcode = 1955AcCry...8..557V}}</ref>
| SpaceGroup = B-form = P2<sub>1</sub>/a<ref name=csba />
| PointGroup = B-form = C{{sup sub|s|2h}}<ref name=csba />
| LattConst_a = 5.591&nbsp;Å
| LattConst_b = 7.404&nbsp;Å
| LattConst_c = 49.38&nbsp;Å (B-form)<ref name=csba />
| LattConst_alpha = 
| LattConst_beta = 117.37
| LattConst_gamma = 
  }}
| Section4       = {{Chembox Thermochemistry
| HeatCapacity = 501.5 J/mol·K<ref name=crc>{{CRC90}}</ref><ref name=nist />
| DeltaHf = −947.7 kJ/mol<ref name=crc />
| DeltaHc = −11342.4 kJ/mol<ref name=pubchem/>
| Entropy = 435.6 J/mol·K<ref name=crc />
  }}
| Section5       = {{Chembox Hazards
| MainHazards = 
| FlashPtC = 205
| AutoignitionPtC = 
| NFPA-H = 1
| NFPA-F = 1
| NFPA-R = 0
| LD50 = 4640 mg/kg (rats, oral)<ref>{{cite web |url=https://hmdb.ca/system/metabolites/msds/000/000/745/original/HMDB00827.pdf |title=Stearic acid MSDS |author=Science Lab.com |access-date=2020-09-30}}</ref><br>21.5 mg/kg (rats, intravenous)<ref name=chemister />
  }}
| Section6       = 
}}
'''Stearic acid''' ({{IPAc-en|ˈ|s|t|ɪər|ɪ|k}} {{respell|STEER|ik}}, {{IPAc-en|s|t|i|ˈ|ær|ɪ|k}} {{respell|stee|ARR|ik}}) is a [[saturated fatty acid]] with an 18-carbon chain.<ref name="pubchem">{{cite web |title=Stearic acid |url=https://pubchem.ncbi.nlm.nih.gov/compound/5281 |publisher=PubChem, US National Library of Medicine |access-date=5 May 2023 |date=29 April 2023}}</ref> The [[IUPAC name]] is '''octadecanoic acid'''.<ref name=pubchem/> It is a soft [[wax]]y solid with the formula {{chem2|CH3(CH2)16COOH}}.<ref name=pubchem/> The [[triglyceride]] derived from three molecules of stearic acid is called [[stearin]].<ref name=pubchem/> 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 {{convert|69.4|C|F}} &nbsp;°C and a [[Acid dissociation constant|pKa]] of 4.50.<ref>{{cite journal |last1=Loften |first1=J.R. |last2=Linn |first2=J.G. |last3=Drackley |first3=J.K. |last4=Jenkins |first4=T.C. |last5=Soderholm |first5=C.G. |last6=Kertz |first6=A.F. |date=August 2014 |title=Invited review: Palmitic and stearic acid metabolism in lactating dairy cows |journal=Journal of Dairy Science |volume=97 |issue=8 |pages=4661–4674 |doi=10.3168/jds.2014-7919 |issn=0022-0302|doi-access=free |pmid=24913651 }}</ref>

Its name comes from the [[Greek language|Greek]] word στέαρ "''stéar''", which means [[tallow]]. The [[Salt (chemistry)|salt]]s and [[ester]]s of stearic acid are called '''stearates'''.<ref name=pubchem/> As its glycerol ester, stearic acid is one of the most common saturated fatty acids found in nature and in the food supply, following [[palmitic acid]].<ref name="hunter">{{cite journal | doi = 10.3945/ajcn.2009.27661| pmid = 19939984| title = Cardiovascular disease risk of dietary stearic acid compared with trans, other saturated, and unsaturated fatty acids: A systematic review| journal = American Journal of Clinical Nutrition| volume = 91| issue = 1| pages = 46–63| year = 2009| last1 = Hunter | first1 = J. E. | last2 = Zhang | first2 = J.| last3 = Kris-Etherton | first3 = P. M. | doi-access = free}}</ref><ref name=lipidhb>Gunstone, F. D., John L. Harwood, and Albert J. Dijkstra "The Lipid Handbook with Cd-Rom. 3rd ed. Boca Raton: CRC Press, 2007. {{ISBN|0849396883}} | {{ISBN|978-0849396885}}</ref> Dietary sources of stearic acid include meat, poultry, fish, eggs, dairy products, and foods prepared with fats; beef [[tallow]], [[lard]], [[butterfat]], [[cocoa butter]], and [[shea butter]] are rich fat sources of stearic acid.<ref name=pubchem/><ref name=hunter/>

== Production ==
In terms of its biosynthesis, stearic acid is produced from [[palmitoyl-CoA]], with [[malonyl-CoA]] a two-carbon building block (after decarboxylation).

Stearic acid is obtained from fats and oils by the [[saponification]] of the triglycerides using hot water (about 100&nbsp;°C). The resulting mixture is then distilled.<ref name=Ullmann>{{Ullmann|doi=10.1002/14356007.a10_245.pub2|isbn=3527306730|title=Fatty Acids|year=2006|last1=Anneken|first1=David J.|last2=Both|first2=Sabine|last3=Christoph|first3=Ralf|last4=Fieg|first4=Georg|last5=Steinberner|first5=Udo|last6=Westfechtel|first6=Alfred}}</ref> Commercial stearic acid is often a mixture of stearic and [[palmitic acid]]s, although purified stearic acid is available. Commercially, [[oleic acid]], as found in [[palm oil|palm]] and [[soybean oil|soy]], can be [[hydrogenated]] 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.<ref name=pubchem/> 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]], and esterification with a range of alcohols.<ref name=pubchem/> This is used in a large range of manufactures, from simple to complex electronic devices.<ref name=pubchem/>

===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).<ref name=hunter/> Stearic acid is more abundant in animal fat (up to 33% in beef liver{{r|lexicon|p=739}}) than in vegetable fat (typically less than 5%).<ref name=hunter/> The important exceptions are the foods [[cocoa butter]] (34%) and [[shea butter]], where the stearic acid content (as a [[triglyceride]]) is 28–45%.<ref name=pubchem/><ref name="lexicon">{{cite journal|year = 2001|title = Lexicon of lipid nutrition (IUPAC Technical Report)|journal = Pure and Applied Chemistry|volume = 73|issue = 4|pages = 685–744|doi = 10.1351/pac200173040685|doi-access=free|last1 = Beare-Rogers|first1 = J.|last2 = Dieffenbacher|first2 = A.|last3 = Holm|first3 = J.V.|s2cid = 84492006}}</ref> Examples of the use of stearic acid in food manufacturing include baked goods, frozen dairy products, [[gelatin]]s, [[pudding]]s, hard candy, and nonalcoholic beverages.<ref name=pubchem/>

Stearic acid ([[E number]] ''E570'') is found in some foods.<ref name=pubchem/><ref>{{cite journal|display-authors=3 |first1=Fernando |last1=Aguilar |first2=Riccardo |last2=Crebelli |first3=Alessandro |last3=Di Domenico |first4=Birgit |last4=Dusemund |first5=Maria Jose |last5=Frutos |first6=Pierre |last6=Galtier |first7=David |last7=Gott |first8=Ursula |last8=Gundert-Remy |first9=Claude |last9=Lambré |first10=Jean-Charles |last10=Leblanc |first11=Oliver |last11=Lindtner |first12=Peter |last12=Moldeus |first13=Alicja |last13=Mortensen |first14=Pasquale |last14=Mosesso |first15=Dominique |last15=Parent-Massin |first16=Agneta |last16=Oskarsson |first17=Ivan |last17=Stankovic |first18=Ine |last18=Waalkens-Berendsen |first19=Rudolf Antonius |last19=Woutersen |first20=Matthew |last20=Wright |first21=Maged |last21=Younes |title=Re-evaluation of fatty acids (E 570) as a food additive |journal=EFSA Journal |date=2017 |volume=15 |issue=5 |page=4785 |doi=10.2903/j.efsa.2017.4785 |pmid=32625490 |pmc=7009963 |url=https://www.efsa.europa.eu/en/efsajournal/pub/4785|doi-access=free}}</ref>

===Soaps and cosmetics===
Stearic acid is mainly used in the production of detergents, soaps, and cosmetics such as [[shampoo]]s and [[shaving cream]] products.<ref name=pubchem/> Stearate soap, such as [[sodium stearate]], could be made from stearic acid but instead are usually produced by [[saponification]] of stearic acid-containing triglycerides. [[Ester]]s of stearic acid with [[ethylene glycol]] ([[glycol stearate]] and [[glycol distearate]]) are used to produce a pearly effect in shampoos, soaps, and other cosmetic products.<ref name=pubchem/>

===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]] is an important component of [[grease (lubricant)|grease]]. The stearate salts of zinc, calcium, cadmium, and lead are used as heat stabilizers for [[PVC]].  Stearic acid is used along with [[castor oil]] 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]]s, e.g. in the production of automobile tires.  As an example, it can be used to make [[casting]]s from a [[plaster]] ''piece mold'' or ''waste mold'', and to make a mold from a [[shellac]]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]], which functions as a release agent.<ref name=Ull2>{{Ullmann|author1=Angelo Nora|author2=Alfred Szczepanek|author3=Gunther Koenen|title=Metallic Soaps|year=2005|doi=10.1002/14356007.a16_361}}</ref>

Stearic acid can be converted to [[zinc stearate]], which is used as a [[lubricant]] for playing cards ([[fanning powder]]) to ensure a smooth motion when [[card manipulation|fanning]]. Stearic acid is a common lubricant during [[injection molding]] and pressing of [[ceramic forming techniques|ceramic powders]].<ref>{{cite journal |title=Influence of stearic acid on suspension structure and green microstructure of injection-molded zirconia ceramics |first=Wenjea J. |last=Tsenga |author2=Mo Liua, Dean |author3=Hsub, Chung-King |journal=Ceramics International|volume=25 |issue=2 |pages=191–195 |year=1999 |doi=10.1016/S0272-8842(98)00024-8}}</ref>

===Niche uses===
Being inexpensive, nontoxic, and fairly inert, stearic acid finds many niche applications.<ref name=pubchem/><ref name=Ullmann/> 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.<ref name=pubchem/>

Stearic acid is used as a negative plate additive in the manufacture of [[Lead–acid battery|lead-acid batteries]].{{citation needed|date=May 2023}} 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]]ity of the negative plate, particularly during dry-charging process. It also reduces the extension of [[redox|oxidation]] 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]]-making. Stearic acid is used along with simple [[sugar]] or [[corn syrup]] as a hardener in [[Candy|candies]].<ref name=pubchem/>

==Metabolism==
An [[isotope labeling]] study in humans<ref>{{cite journal|last = Emken|first = Edward A.|year = 1994|title = Metabolism of dietary stearic acid relative to other fatty acids in human subjects|journal = American Journal of Clinical Nutrition|volume = 60|pages = 1023S–1028S|pmid = 7977144|issue = 6|doi = 10.1093/ajcn/60.6.1023S|doi-access = free}}</ref> concluded that the fraction of dietary stearic acid that [[redox|oxidatively]] desaturates to [[oleic acid]] is 2.4 times higher than the fraction of [[palmitic acid]] analogously converted to [[palmitoleic acid]].
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]] [[cholesterol]] in comparison with other saturated fatty acids.<ref name=hunter/>

===Examples===
;Salts
*[[Potassium stearate]]
* [[Calcium stearate]]
* [[Cobaltous stearate]]
* [[Lithium stearate]]
* [[Magnesium stearate]]
* [[Mercuric stearate]]
* [[Sodium stearate]]
* [[Zinc stearate]]
;Esters
* [[Estradiol stearate]]
* [[Glycol stearate]]
* [[Stearin]]
* [[Testosterone stearate]]

==References==
{{reflist}}

==External links==
{{Commons category|Stearic acid}}
*[http://webbook.nist.gov/cgi/cbook.cgi?Name=stearic+acid&Units=SI NIST Chemistry WebBook Entry]

{{Stearates}}
{{Fatty acids}}
{{Lipids}}
{{Palm oil}}

{{Authority control}}

[[Category:Fatty acids]]
[[Category:Stearates]]
[[Category:Alkanoic acids]]
[[Category:E-number additives]]