Stearic acid

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Structural formula
Structural formula of stearic acid
General
Surname Stearic acid
other names
  • Octadecanoic acid ( IUPAC )
  • n- octadecanoic acid
  • Sebum acid ( obsolete )
  • Lactaric acid (obsolete)
  • Stearophanic acid (obsolete)
  • STEARIC ACID ( INCI )
Molecular formula C 18 H 36 O 2
Brief description

white, tasteless solid

External identifiers / databases
CAS number 57-11-4
EC number 200-313-4
ECHA InfoCard 100,000,285
PubChem 5281
ChemSpider 5091
DrugBank DB03193
Wikidata Q209685
properties
Molar mass 284.48 g mol −1
Physical state

firmly

density

0.94 g cm −3

Melting point

69.2-69.9 ° C

boiling point

370 ° C

Vapor pressure

9.5 · 10 −8 Pa (298 K)

solubility
Refractive index

1.4299 (80 ° C)

safety instructions
GHS labeling of hazardous substances
no GHS pictograms
H and P phrases H: no H-phrases
P: no P-phrases
MAK

not rated

Toxicological data

> 2,000 mg kg −1 ( LD 50 ,  rat ,  oral )

Thermodynamic properties
ΔH f 0

−949 kJ mol −1

As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C

Stearic acid is a saturated carboxylic and fatty acid . Their salts and esters are called stearates (systematically also octadecanoates ). Stearic acid is often incorrectly called stearin .

Stearic acid

Extraction and presentation

Stearic acid can be obtained from vegetable and animal oils and fats by saponification . Fat is cooked together with caustic soda and hydrolyzed into glycerine and the sodium salt of fatty acids ( soap ) . These fatty acid salts are converted back into fatty acids with mineral acids. Since fats usually contain a mixture of different glycerol esters of fatty acids, they have to be separated by distillation or are used as a mixture.

Chemical properties

Stearic acid is a very weak acid . Aqueous solutions of their alkali salts have a strong alkaline reaction.

use

Stearic acid is used as an additive in the automotive, food and drug industries. Stearin candles are made of stearic acid. Shaving foam often contains stearic acid. The sodium salt sodium stearate is used as a cleaning agent. Stearic acid is the starting material for the manufacture of various detergents. In the EU it is generally approved as a food additive (under the number E570 as a collective name for fatty acids) without maximum quantity restriction (quantum satis) for foodstuffs .

Occurrence

The acid occurs in the form of glycerol stearate in almost all animal and vegetable fats and oils, including hazelnuts and cocoa butter (30–37%). In particular, in the triacylglycerols of animal fats, besides palmitic acid, it is the dominant saturated fatty acid in terms of quantity: beef tallow (20–35%), mutton tallow (15–30%), pork lard (12–18%), butter fat (9–13%) . Vegetable lipids sometimes contain very high amounts, occasionally up to approx. 60–70% of stearic acid.

Contrary to popular belief, these natural fats and oils do not contain free stearic acid, but its glycerol esters .

Individual evidence

  1. ↑ Entry on STEARIC ACID in the CosIng database of the EU Commission, accessed on March 11, 2020.
  2. ↑ a b c d Entry on stearic acid. In: Römpp Online . Georg Thieme Verlag, accessed on March 26, 2010.
  3. ↑ a b c d e Entry on stearic acid in the GESTIS substance database of the IFA , accessed on December 20, 2019 (JavaScript required)
  4. ^ Albin H. Warth: The Chemistry and Technology of Waxes. Second Edition, Reinhold Publ., 1956, p. 34, online at babel.hathitrust.org, accessed November 6, 2017.
  5. ↑ CD Cappa, ER Lovejoy, AR Ravishankara: Evaporation Rates and Vapor Pressures of the Even-Numbered C 8 −C 18 Monocarboxylic Acids. In: J. Phys. Chem. A 112, (2008), pp. 3959-3964, doi : 10.1021 / jp710586m .
  6. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Organic Compounds, pp. 3-462.
  7. ↑ Stearic acid data sheet from Sigma-Aldrich , accessed on August 30, 2012 ( PDF ).
  8. ^ Basic thermodynamic data: enthalpy of formation and standard entropy (PDF; 54 kB). ( Memento of the original from February 21, 2014 in the Internet Archive ) Info: The @1@ 2Template: Webachiv / IABot / www.ksk.ch archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. ksk.ch, accessed on September 19, 2013.
  9. ↑ Franz v. Bruchhausen, G. Dannhardt, Siegfried Ebel, August-Wilhelm Frahm, Eberhard Hackenthal, Ulrike Holzgrabe: Hager's handbook of pharmaceutical practice . 5th edition. Springer, 1994, ISBN 978-3-642-63389-8 , pp. 657 ( limited preview in Google Book search).
  10. ↑ Emil Abderhalden (Ed.): Biochemisches Handlexikon . Volume VIII (1st supplementary volume). Springer, 1914, ISBN 978-3-642-88971-4 , pp. 241 ( limited preview in Google Book search).
  11. ↑ Walther Schrauth : Handbook of soap manufacturing . 6th edition. Springer, 1927, ISBN 978-3-662-35437-7 , pp. 18 ( limited preview in Google Book search).
  12. ^ August Chwala: Textile auxiliaries . Springer, 1939, ISBN 978-3-7091-5256-0 , pp. 110 ( limited preview in Google Book search).
  13. ↑ Octadecanoic acid at PlantFA Database, accessed November 6, 2017.

Web links

Wiktionary: stearic acid  - explanations of meanings, word origins, synonyms, translations