Stearin

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Stearin[1]
Skeletal formula of stearin
Space-filling model of the tristearin molecule
Powder of stearin
Names
Systematic IUPAC name
Propane-1,2,3-triyl tri(octadecanoate)
Other names
Tristearin; Trioctadecanoin; Glycerol tristearate; Glyceryl tristearate
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
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KEGG
UNII
  • {{#property:P3117}}Lua error in Module:EditAtWikidata at line 29: attempt to index field 'wikibase' (a nil value).
  • InChI=1S/C57H110O6/c1-4-7-10-13-16-19-22-25-28-31-34-37-40-43-46-49-55(58)61-52-54(63-57(60)51-48-45-42-39-36-33-30-27-24-21-18-15-12-9-6-3)53-62-56(59)50-47-44-41-38-35-32-29-26-23-20-17-14-11-8-5-2/h54H,4-53H2,1-3H3 ☒N
    Key: DCXXMTOCNZCJGO-UHFFFAOYSA-N ☒N
  • InChI=1S/C57H110O6/c1-4-7-10-13-16-19-22-25-28-31-34-37-40-43-46-49-55(58)61-52-54(63-57(60)51-48-45-42-39-36-33-30-27-24-21-18-15-12-9-6-3)53-62-56(59)50-47-44-41-38-35-32-29-26-23-20-17-14-11-8-5-2/h54H,4-53H2,1-3H3
    Key: DCXXMTOCNZCJGO-UHFFFAOYSA-N
  • CCCCCCCCCCCCCCCCCC(=O)OCC(COC(=O)CCCCCCCCCCCCCCCCC)OC(=O)CCCCCCCCCCCCCCCCC
Properties
C57H110O6
Molar mass 891.501 g·mol−1
Appearance White powder
Odor Odorless
Density
  • 0.862 g/cm3 (80 °C)
  • 0.8559 g/cm3 (90 °C)[2]
Melting point 54–72.5 °C (129.2–162.5 °F; 327.1–345.6 K)[3]
Insoluble
Solubility
1.4395 (80 °C)[2]
Structure
Triclinic (β-form)[4]
P1 (β-form)[4]
a = 12.0053 Å, b = 51.902 Å, c = 5.445 Å (β-form)[4]
α = 73.752°, β = 100.256°, γ = 117.691°
Thermochemistry
  • 1342.8 J/mol·K (β-form, 272.1 K)
  • 1969.4 J/mol·K (346.5 K)[3][5]
1534.7 J/mol·K (liquid)[5]
−2344 kJ/mol[5]
35806.7 kJ/mol[5]
Hazards
NFPA 704 (fire diamond)
[6]
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 ≥ 300 °C (572 °F; 573 K) closed cup[6]
Lethal dose or concentration (LD, LC):
2000 mg/kg (rats, oral)[6]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Stearin /ˈstɪərɪn/, 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.[7] Like other triglycerides, stearin can crystallise in three polymorphs. For stearin, these melt at 54 °C (α-form), 65 °C, and 72.5 °C (β-form).[3]

Note that stearin is also used to mean the solid component of an oil or fat that can be separated into components that melt at higher (the stearin) and lower (the olein) temperatures. This is the usage meant in an example such as palm stearin.

Occurrence

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Stearin is obtained from animal fats created as a byproduct of processing beef. It can also be found in tropical plants such as palm. It can be partially purified by dry fractionation by pressing tallow or other fatty mixtures, leading to separation of the higher melting stearin-rich material from the liquid, which is typically enriched in fats derived from oleic acid. It can be obtained by interesterification, again exploiting its higher melting point which allows the higher melting tristearin to be removed from the equilibrated mixture. Stearin is a side product obtained during the extraction of cod liver oil removed during the chilling process at temperatures below −5 °C.

Uses

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Stearin is used as a hardening agent in the manufacture of candles and soap.[8] It is mixed with a sodium hydroxide solution in water, creating a reaction which gives glycerin and sodium stearate, the main ingredient in most soap:

C3H5(C18H35O2)3 + 3 NaOH → C3H5(OH)3 + 3 C18H35OONa

Stearin is also added to aluminium flakes to help in the grinding process in making dark aluminium powder.[clarification needed]

See also

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References

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  1. ^ Merck Index, 11th Edition, 9669.
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  5. ^ a b c d Tristearin 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 2014-06-19)
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