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| PIN = Octadecanoic acid <!-- Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book) -->
| PIN = Octadecanoic acid <!-- Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book) -->
| SystematicName =
| SystematicName =
| OtherNames = Stearic acid<br />C18:0 ([[Lipid number]]s)
| OtherNames = {{Unbulleted list|Stearic acid|C18:0 ([[Lipid number]]s)}}
| IUPACName =
| IUPACName =
| Section1 = {{Chembox Identifiers
| Section1 = {{Chembox Identifiers
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| BoilingPt_notes = <br> decomposes<br> {{convert|232|C|F K}}<br> at 15 mmHg<ref name=crc />
| BoilingPt_notes = <br> decomposes<br> {{convert|232|C|F K}}<br> at 15 mmHg<ref name=crc />
| Solubility = 0.00018 g/100 g (0 °C)<br> 0.00029 g/100 g (20 °C)<br>0.00034 g/100 g (30 °C)<br> 0.00042 g/100 g (45 °C)<br> 0.00050 g/100 g (60 °C)<ref name="Ralston">{{cite journal|year = 1942|title = The Solubilities of the Normal Saturated Fatty Acids|journal = The Journal of Organic Chemistry|volume = 7|issue = 6|pages = 546–555|doi = 10.1021/jo01200a013|last1 = Ralston|first1 = A.W.|last2 = Hoerr|first2 = C.W.|pmid = 20280727}}</ref>
| Solubility = 0.00018 g/100 g (0 °C)<br> 0.00029 g/100 g (20 °C)<br>0.00034 g/100 g (30 °C)<br> 0.00042 g/100 g (45 °C)<br> 0.00050 g/100 g (60 °C)<ref name="Ralston">{{cite journal|year = 1942|title = The Solubilities of the Normal Saturated Fatty Acids|journal = The Journal of Organic Chemistry|volume = 7|issue = 6|pages = 546–555|doi = 10.1021/jo01200a013|last1 = Ralston|first1 = A.W.|last2 = Hoerr|first2 = C.W.|pmid = 20280727}}</ref>
| SolubleOther = Soluble in alkyl [[acetate]]s, [[Alcohol (chemistry)|alcohol]]s, [[methyl formate|HCOOCH<sub>3</sub>]], [[phenyl group|phenyl]]s, [[carbon disulfide|CS<sub>2</sub>]], [[carbon tetrachloride|CCl<sub>4</sub>]]<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>
| 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 />
| 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
| Solvent1 = dichloromethane
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}}
}}
| Section3 = {{Chembox Structure
| 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.}}</ref>
| 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 />
| SpaceGroup = B-form = P2<sub>1</sub>/a<ref name=csba />
| PointGroup = B-form = C{{sup sub|s|2h}}<ref name=csba />
| PointGroup = B-form = C{{sup sub|s|2h}}<ref name=csba />
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| HeatCapacity = 501.5 J/mol·K<ref name=crc>{{CRC90}}</ref><ref name=nist />
| HeatCapacity = 501.5 J/mol·K<ref name=crc>{{CRC90}}</ref><ref name=nist />
| DeltaHf = −947.7 kJ/mol<ref name=crc />
| DeltaHf = −947.7 kJ/mol<ref name=crc />
| DeltaHc = −11342.4 kJ/mol<ref name=pubchem/>
| DeltaHc = −11342.4 kJ/mol<ref>National Center for Biotechnology Information (2021). PubChem Compound Summary for CID 5281, Stearic acid. Retrieved January 7, 2021 from https://pubchem.ncbi.nlm.nih.gov/compound/Stearic-acid.</ref>
| Entropy = 435.6 J/mol·K<ref name=crc />
| Entropy = 435.6 J/mol·K<ref name=crc />
}}
}}
| Section5 = {{Chembox Hazards
| Section5 = {{Chembox Hazards
| MainHazards =
| MainHazards =
| FlashPtC = 113
| FlashPtC = 205
| AutoignitionPtC =
| AutoignitionPtC =
| NFPA-H = 1
| NFPA-H = 1
Line 90: Line 90:
| Section6 =
| 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. The [[IUPAC name]] is '''octadecanoic acid'''. It is a [[wax]]y solid with the formula {{chem2|CH3(CH2)16CO2H}}. 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'''. As its ester, stearic acid is one of the most common saturated fatty acids found in nature following [[palmitic acid]].<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> The [[triglyceride]] derived from three molecules of stearic acid is called [[stearin]].
'''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)16CO2H}}.<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 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 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/>
== Occurrence and production ==
⚫
Stearic acid is more abundant in animal fat (up to 30%) than in vegetable fat (typically <5%). The important exceptions are the foods [[cocoa butter]] (34%)<ref>{{Cite web|title=硬脂酸;十八烷酸;十八酸;十八碳烷酸;Stearic acid;Octadecanoic acid;物理性质,化学性质,英文名,分子量,结构式,分子式,CAS号,制备方法,用途,溶点,沸点,毒性,MSDS,供应商,公司|url=http://www.chemyq.com/xz/xz12/116648yvdhe.htm|access-date=2020-06-17|website=www.chemyq.com}}</ref> and [[shea butter]], where the stearic acid content (as a [[triglyceride]]) is 28–45%.<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>


== Production ==
In terms of its biosynthesis, stearic acid is produced from carbohydrates via the [[fatty acid synthesis]] machinery wherein [[acetyl-CoA]] contributes two-carbon building blocks.<ref>{{cite web | title= Fatty Acids: Straight-chain Saturated, Structure, Occurrence and Biosynthesis| publisher= Lipid Library, The American Oil Chemists' Society | date= 30 April 2011| website= lipidlibrary.aocs.org| url= http://lipidlibrary.aocs.org/lipids/fa_sat/index.htm | archiveurl= https://web.archive.org/web/20110721024641/http://lipidlibrary.aocs.org/lipids/fa_sat/index.htm |archivedate=21 July 2011 }}</ref>
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.
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==
==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]], and esterification with a range of alcohols. This is used in a large range of manufactures, from simple to complex electronic devices.{{Cn|date=February 2021}}
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/>


===As food additive===
===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>{{cite journal |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>


⚫
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, cosmetics, detergents===

⚫
Stearic acid is mainly used in the production of detergents, soaps, and cosmetics such as [[shampoo]]s and [[shaving cream]] products. 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. Detergents are obtained from amides and quaternary alkylammonium derivatives of stearic acid.{{Cn|date=February 2021}}
⚫
===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===
===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 stabilisers [[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>
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 stabilisers [[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>


Steric 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> It is also used as a mold release for [[foam latex]] that is baked in stone molds.{{Cn|date=February 2021}}
Steric 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===
===Niche uses===
Being inexpensive, nontoxic, and fairly inert, stearic acid finds many niche applications.<ref name=Ullmann/> Stearic acid is used as a negative plate additive in the manufacture of [[Lead–acid battery|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]]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]]. In [[fireworks]], stearic acid is often used to coat [[metal]] powders such as [[aluminium]] and [[iron]]. This prevents oxidation, allowing compositions to be stored for a longer period of time.{{Cn|date=February 2021}}
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==
==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}}</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]].
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]].
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>{{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>
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===
===Examples===
;Salts
;Salts
*[[Potassium stearate]]
* [[Calcium stearate]]
* [[Calcium stearate]]
* [[Cobaltous stearate]]
* [[Cobaltous stearate]]

Latest revision as of 08:03, 31 May 2024

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 100.000.285 Edit this at Wikidata
EC Number
  • 200-313-4
KEGG
RTECS number
  • WI2800000
UNII
  • CCCCCCCCCCCCCCCCCC(=O)O
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]
0.00018 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]
Solubility in dichloromethane 3.58 g/100 g (25 °C)
8.85 g/100 g (30 °C)
18.3 g/100 g (35 °C)[4]
Solubility in hexane 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 in ethanol 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 in acetone 4.73 g/100 g[5]
Solubility in chloroform 15.54 g/100 g[5]
Solubility in toluene 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]
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 dose or 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 their standard state (at 25 °C [77 °F], 100 kPa).

Stearic acid (/ˈstɪərɪk/ STEER-ik, /stiˈærɪk/ stee-ARR-ik) is a saturated fatty acid with an 18-carbon chain.[9] The IUPAC name is octadecanoic acid.[9] It is a soft waxy solid with the formula CH3(CH2)16CO2H.[9] The triglyceride derived from three molecules of stearic acid is called stearin.[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 the Greek word στέαρ "stéar", which means tallow. The salts and esters of stearic acid are called stearates.[9] 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.[12][13] 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.[9][12]

Production

[edit]

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 °C). The resulting mixture is then distilled.[14] Commercial stearic acid is often a mixture of stearic and palmitic acids, although purified stearic acid is available. Commercially, oleic acid, as found in palm and soy, can be hydrogenated to 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 to stearyl 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 foods cocoa butter (34%) and shea butter, where the stearic acid content (as a triglyceride) 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 number E570) 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 as shampoos and shaving cream products.[9] Stearate soap, such as sodium stearate, could be made from stearic acid but instead are usually produced by saponification of stearic acid-containing triglycerides. Esters 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.[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 stearate is an important component of grease. The stearate salts of zinc, calcium, cadmium, and lead are used as heat stabilisers 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 agents, e.g. in the production of automobile tires. As an example, it can be used to make castings from a plaster piece mold or waste mold, and to make a mold from a shellacked 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.[17]

Steric acid can be converted to zinc stearate, which is used as a lubricant for playing cards (fanning powder) to ensure a smooth motion when fanning. Stearic acid is a common lubricant during injection molding and pressing of ceramic 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 of lead-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 the hydrophobicity of the negative plate, particularly during dry-charging process. It also reduces the extension of 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 candies.[9]

Metabolism

[edit]

An isotope labeling study in humans[19] concluded that the fraction of dietary stearic acid that 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.[12]

Examples

[edit]
Salts
Esters

References

[edit]
  1. ^ Susan Budavari, ed. (1989). Merck Index (11th ed.). Rahway, New Jersey: Merck & Co., Inc. p. 8761. ISBN 978-0-911910-28-5.
  2. ^ a b c d e f g h Lide, David R., ed. (2009). CRC Handbook of Chemistry and Physics (90th ed.). Boca Raton, Florida: CRC Press. ISBN 978-1-4200-9084-0.
  3. ^ a b Ralston, 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. PMID 20280727.
  4. ^ a b c d "stearic acid". Chemister.ru. 2007-03-19. Retrieved 2017-06-30.
  5. ^ a b c Seidell, Atherton; Linke, William F. (1919). Solubilities of Inorganic and Organic Compounds (2nd ed.). D. Van Nostrand Company. p. 677.
  6. ^ a b Octadecanoic acid in 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. ISBN 978-0-8493-9345-7.
  8. ^ a b c d von 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. ^ a b c d e f g h i j k l m n o p q r "Stearic acid". PubChem, US National Library of Medicine. 29 April 2023. Retrieved 5 May 2023.
  10. ^ Science Lab.com. "Stearic acid MSDS" (PDF). Retrieved 2020-09-30.
  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. ISSN 0022-0302. PMID 24913651.
  12. ^ a b c d e Hunter, 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. PMID 19939984.
  13. ^ 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
  14. ^ a b Anneken, 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. ISBN 3527306730.
  15. ^ a b Beare-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. S2CID 84492006.
  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. PMC 7009963. PMID 32625490.
  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. ISBN 978-3527306732.
  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. PMID 7977144.
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