This reactivity increases as the number of double bonds increases. Conjugated Non-conjugated With the bonds in a conjugated position, there is a further increase in certain types of chemical reactivity. For example, fats are much more subject to oxidation and polymerization when bonds are in the conjugated position. Polyunsaturated Fatty Acids. Of the polyunsaturated fatty acids, linoleic, linolenic, arachidonic, eicosapentaenoic, and docosahexaenoic acids containing respectively two, three, four, five, and six double bonds are of most interest.
Vegetable oils are the principal sources of linoleic and linolenic acids.
Fish oils contain large quantities of a variety of longer chain fatty acids having three or more double bonds including eicosapentaenoic and docosahexaenoic acids. A number of saturated odd and even chain acids are present in trace quantities in many fats and oils. C. Isomerism of Unsaturated Fatty Acids Isomers are two or more substances composed of the same elements combined in the same proportions but differing in molecular structure. Unsaturated fatty acids can exist in either the cis or trans form depending on the configuration of the hydrogen atoms attached to the carbon atoms joined by the double bonds. If the hydrogen atoms are on the same side of the carbon chain, the arrangement is called cis .