PRODUCTS OF DIMERIZATION OF UNSATURATED FATTY-ACIDS .11. THE FRACTION OF ALICYCLIC DIMERIC ACIDS

Dimeric fatty acids can be separated as their dimethylates by HPLC-chromatography [W. Link, G. Spiteller, Fat Sci. Technol. 92, 135 (1990)]. The main fraction of dimeric fatty acids obtained by the dimerisation of linoleic acid consists of alicyclic unsaturated dimeric fatty acids with the molecular weights 588 and 590. The structures of these compounds remained unknown until now. This fraction was subjected to hydrogenation, epoxidation and dehydrogenation with SeO2 and Pd/C. The investigation of the reaction products provided evidence that these dimeric acids are a mixture of the following compounds: Dimeric acids with a 6-ring and one double bond and dimeric acids with two 6-rings and a double bond could be identified. In both types of compounds the double bond can be either situated in the ring as well as outside the ring. In dimeric acids containing two rings this ring system can be condensed or separated by a C-chain. Besides dimeric acids with two 6-rings dimeric acids with one 6-ring and one 5-ring were found. Essential contributions to these deductions were obtained by an investigated of model compounds and model fractions.