Oleic acid

• (Z )-9- octadecenoic acid (IUPAC)
• Cis-9- octadecenoic
• Oleic acid
• 18:1 ( ω -9) (lipid Name )

Colorless and odorless liquid

Liquid

0.89 g · cm -3

17 ° C

360 ° C.

1.9 x 10-6 Pa ( 298 K)

Insoluble in water, soluble in methanol

1.4582 (20 ° C)

Not yet determined

Template: Infobox chemical / molecular formula search available

Oleic acid, and oleic acid, is the main agent of monounsaturated fatty acids (18:1). Your systematic name is ( Z )-9- octadecenoic acid and it is due to the location of their double bond, an omega -9 fatty acid. A naturally occurring isomer of oleic acid is the petroselinic acid, the trans isomer is called elaidic acid. The salts and esters of oleic acid known as oleates.

Occurrence

Oleic acid is chemically bound in front of triglycerides in nearly all natural ( plant and animal ) oils and fats. A particularly high proportion of such esterified oleic acid have, for example olive oil ( 70-75 %), peanut oil ( 50-70%), rapeseed oil (HEAR varieties 12-24 %, LEAR varieties 50-65 %), avocado oil ( 44-76 %), goose fat ( 41-72 % ), palm oil ( 37-42 %), lard ( 36-52 %), sesame oil ( 35-46 %), mutton ( 31-56 %), beef tallow (26 - 45% ), sunflower oil ( 14-65 %) and, in particular so-called high-oleic sunflower oil from specially bred varieties with 75-93 % oleic acid content.

Contrary to popular perception, these natural fats and oils contain no free oleic acid, but their glycerol esters.

Production and representation

The fatty acids can be obtained by alkaline hydrolysis of the corresponding triacylglycerols by the corresponding fats or oils are boiled with bases. The hydrolysis itself initially provides their salts. The free fatty acids are obtained by neutralization with (mineral) acid. Since the natural fats and oils always contain many different fatty acids, joins usually a separation by distillation of the resulting mixture to.

Commercial Oleic acid is obtained via hydrolysis and subsequent crystallization from tallow. Through this process, a concentration of about 70% can be obtained, which are called olein. As well as oleic acid, palmitoleic acid, linoleic acid and other unsaturated and saturated fatty acids may be included in this mixture. By hydrolyzing very high oleic vegetable oils such as olive oil, Euphorbia lathyris or high-oleic sunflower purities can be obtained by more than 90 %.

Properties

Physical Properties

Pure oleic acid is a colorless, oily and almost odorless liquid. The molar mass is 282.46 g mol -1, and the density of 0.89 g · cm - 3 having a melting point of 17 ° C and a boiling point of 360 ° C. The fatty acid is insoluble in water but soluble in methanol.

Chemical Properties

Oleic acid, as compared to polyunsaturated fatty acids (e.g. linoleic acid ) is only slightly sensitive to oxidation. They slowly oxidize in air under yellow coloring which is due to the formation of decomposition products. Major target of oxidation is the CC double bond. She will be promoted particularly by light, heat or dissolved metal ions and proceeds mainly via radical reaction mechanisms. Important intermediate step of oxidation is the formation of hydroperoxides ( -OOH ) in breaking the carbon-carbon double bond. The functional group ( -OOH ) is itself also radicals, thus promoting an oxidative chain reaction. Next can decompose to ketones and, if it comes to cleavage of the simple C -C bond, even to aldehydes or carboxylic acids hydroperoxides.

Oleic acid, and especially their salts are amphiphilic, meaning they contain both a polar, hydrophilic part ( the carboxyl group ) and a non-polar, lipophilic portion ( hydrocarbon chain).

Proof

The detection and assay of oleic acid as well as other fatty acids in the fats is carried out usually by gas chromatography of the methyl esters; supplement can be a separation of the unsaturated isomers with silver nitrate thin layer chromatography. A second detection method is the Bromwasserprobe. As a result one has a disappearance of the brown color.

Use

Oleic acid is used as a component of mixtures with other fatty acids in varying proportions, especially the manufacture of soaps and metal soaps and for surfactant production.