Stearolic acid

Stearolic acid

File:Stearolic acid.png
Names
IUPAC name octadec-9-ynoic acid
Other names 9-octadecynoic acid
Identifiers
CAS Number	506-24-1 ☒N
3D model (JSmol)	Interactive image
ChEBI	CHEBI:28801
ChEMBL	ChEMBL482804
ChemSpider	61475
ECHA InfoCard
EC Number	208-030-8
E number
KEGG	C08459
PubChem CID	68167
UNII	7M9KFA3WKU
CompTox Dashboard (EPA)	DTXSID90198647
InChI 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
SMILES CCCCCCCCC#CCCCCCCCC(=O)O
Properties
Chemical formula	C18H32O2
Molar mass	280.452 g·mol−1
Appearance	solid
Melting point	45 °C (113 °F; 318 K)
Solubility in water	practically insoluble
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

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. Its delta notation is 18:1Δ9a.

Stearolic acid is classified as an octadecynoic acid, 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.

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.

File: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.

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.

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.

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.