Derivation: The name for linoleic acid, as with α-linolenic acid, derives from Limun usitatissium (common name the flax plant) which is a known rich dietary source of the fatty acid.
Chemical name: cis-n-6,9-octadecadionoic acid, cis-∆-9,12-octadecadionoic acid; C18:2n-6
Proper name: linoleic acid
Structure, and classification
Linoleic acid is polyunsaturated fatty acid with 18 carbons and two double bonds. The first double bond is 6 carbon molecules from the omega (n-, ω-) (methyl) carbon, with the other double bond methylene interrupted (on carbon 9). From the delta (∆-) end, the first double bond is 9 carbons from the carboxyl carbon with the other double bond methylene interrupted (on carbons 12). The classification of LA is therefore as an omega-6 or delta-9 fatty acid. The placement of the double bonds on the fatty acid chain are in the cis-configuration, and this gives the molecule a pronounced curvature due to the repulsion of the hydrogen molecules on the same side of the molecule. However, due to the presence of only two double bonds, this curvature is not as great as seen with α-linolenic acid. The structure of LA is shown in figure 1.
Figure 1. The structure of the essential fatty acid linoleic acid. The placement of the double bonds with the cis-configuration produces a curvature in the molecule.