Stearolic acid

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Stearolic acid
Stearolic acid.png
Names
IUPAC name
octadec-9-ynoic acid
Other names
9-octadecynoic acid
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.007.301 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 208-030-8
KEGG
PubChem CID
UNII
  • InChI=1S/C18H32O2/c1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18(19)20/h2-8,11-17H2,1H3,(H,19,20)
    Key: RGTIBVZDHOMOKC-UHFFFAOYSA-N
  • CCCCCCCCC#CCCCCCCCC(=O)O
Properties
C18H32O2
Molar mass 280.452 g·mol−1
Appearancesolid
Melting point 45 °C (113 °F; 318 K)
practically insoluble
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Stearolic acid is an acetylenic fatty acid characterized by an 18-carbon chain with a triple bond between carbons 9 and 10. It is a rare, naturally occurring unsaturated fatty acid, notable for its unique chemical structure and occurrence in certain plant species. Its structural formula is CH3(CH2)7C≡C(CH2)7COOH. [1] Its delta notation is 18:1Δ9a.

Contents

Stearolic acid is classified as an octadecynoic acid, [2] specifically with the triple bond at the 9-position, hence its common name, 9-octadecynoic acid. The acid is isomeric to linoleic acid and tartaric acid, the latter differing from stearolic acid only in the position of the triple bond. Stearic acid, which has a similar name, has the same chain length but is saturated.

Natural occurrence

Stearolic acid has been reported to occur in lipids of plant origin, in particular in the seed oil of Pyrularia edulis , Pyrularia pubera , Santalum album , Santalum acuminatum , Acanthosyris spinescens , and Exocarpus cupressiformis . Oils with a high stearolic acid content are drying oils that polymerize in relatively short times.

Its presence in these plants is relatively rare compared to more common fatty acids, such as stearic and oleic acids.

Stearolic acid is considered to be the main precursor of other acetylenic fatty acids, in particular ximenynic acid and exocarpic acid, with which it is frequently identified. [3] [4]

Synthesis

Stearolic acid can be synthesized from oleic acid through a process involving halogenation followed by double dehydrohalogenation, which introduces the acetylenic triple bond into the fatty acid chain. [5] [6]

The oleic to stearolic acid path Oleic to stearolic acid.svg
The oleic to stearolic acid path

Physical properties

The acid is practically insoluble in water, but readily soluble in diethyl ether and hot ethanol. [7]

Stearolic acid crystallizes in the monoclinic crystal system in the space group C 2h with the lattice parameters a = 9.551 Å; b = 4.686 Å, c = 49.15 Å and β = 53.4° and four formula units per unit cell. [8]

Chemical properties

Ozonolysis of stearolic acid yields 9,10-dioxostearic acid. This can also be formed by reacting stearolic acid with potassium permanganate, although depending on the pH-value, oxidative cleavage also occurs. [9]

When reacted with molten potassium hydroxide, stearolic acid decomposes into myristic acid and acetic acid.

Biological and chemical significance

Acetylenic fatty acids like stearolic acid are of interest for their unique chemical reactivity and potential biological activities. However, detailed studies on the biological roles and applications of stearolic acid are limited compared to more common fatty acids.

References

  1. ↑ Thomasson, H. J. (March 1954). "Stearolic Acid, an Essential Fatty Acid?". Nature . 173 (4401): 452. Bibcode:1954Natur.173..452T. doi:10.1038/173452a0. ISSN   1476-4687. PMID   13144781 . Retrieved 25 April 2025.
  2. ↑ "9-Octadecynoic acid". NIST . Retrieved 25 April 2025.
  3. ↑ Hettiarachchi, D. S.; Liu, Y. D.; Boddy, M. R.; Fox, J. E. D.; Sunderland, V. B. (2013). "Contents of Fatty Acids, Selected Lipids and Physicochemical Properties of Western Australian Sandalwood Seed Oil" . Journal of the American Oil Chemists' Society . 90 (2): 285–290. doi:10.1007/s11746-012-2162-3. ISSN   1558-9331 . Retrieved 25 April 2025.
  4. ↑ John, Isaac (1 July 2000). "Wink M. 1999. Biochemistry of plant secondary metabolism. Annual plant reviews, Volume 2 . 374 pp. Sheffield: Sheffield Academic Press Ltd. £85 (hardback) and Functions of plant secondary metabolites and their exploitation in biotechnology. Annual plant reviews, Volume 3 . 370 pp. Sheffield: Sheffield Academic Press Ltd. £79 (hardback)". Annals of Botany . 86 (1): 208–209. Bibcode:2000AnBot..86..208J. doi:10.1006/anbo.2000.1196. ISSN   0305-7364 . Retrieved 25 April 2025.
  5. ↑ Armstrong, Henry Edward (1876). Introduction to the Study of Organic Chemistry: The Chemistry of Carbon and Its Compounds. D. Appleton. p. 293. Retrieved 25 April 2025.
  6. ↑ Watts, Henry (1872). A Dictionary of Chemistry and the Allied Branches of Other Sciences. Longmans, Green, and Company. p. 1038. Retrieved 25 April 2025.
  7. ↑ "Stearolic acid". chemister.ru. Retrieved 25 April 2025.
  8. ↑ Müller, Alex; Bragg, William Lawrence (January 1997). "An X-ray investigation of certain long-chain compounds". Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character . 114 (768): 542–561. doi: 10.1098/rspa.1927.0057 .
  9. ↑ Ackman, R. G.; Dytham, R. A.; Wakefield, B. J.; Weedon, B. C. L. (1 January 1960). "Organic reactions in strong alkalis-II: Fission of di-ethylenic and acetylenic acids" . Tetrahedron . 8 (3): 239–245. doi:10.1016/0040-4020(60)80032-4. ISSN   0040-4020 . Retrieved 25 April 2025.
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