LIPIDES 77 



TABLE 4-1. (Continued) 



Name 

 • Structural 



Common Systematic Formula 



C. Linolenic Acid Series 



Linolcnic 9,12,1 5-Octadecatrienoic C17H29COOH 



Eleostearic 9,11,13-Octadecatrienoic C17H29COOH 



D. Arachidonic Series 



Parinaric 9,11,13,15-Octadecatetraenoic C17H27COOH 



Arachidonic 5,8,11,14-Eicosatetraenoic C19H31COOH 



E. Clupanodonic Series 



Clupanodonic 4,8,12,15,19-Docosapentaenoic C21H33COOH 



III. Unsaturated Monohydroxy Fatty Acids — Ricinoleic Series 

 Ricinoleic 12-Hydroxy-9-octadecenoic C17H32OHCOOH 



IV. Cyclic Fatty Acids — Chaulmoogric Scries 

 Hydnocarpic 11-A^-Cyclopentenyl-n-undecanoic acid C15H27COOH 



Chaulmoogric 1 S-A^-Cyclopentenyl-w-tridecanoic acid C17H31COOH 



sattirated fatty acid. One of the outstanding effects is on the melting 

 point of the acid. Whereas stearic acid melts at 69.6°C., oleic acid 

 melts at 13°C. Linolic and linolenic acids melt at — 5°C. and 

 — 14.5°C., respectively. Thus, the introduction of one or more double 

 bonds in a long-chain fatty acid produces a compound which is liquid 

 at 20°C. The liquid state of most vegetable fats can be attributed to 

 large percentages of unsaturated fatty acid components. 



Unsaturated fatty acids are far more chemically reactive than their 

 saturated analogues. For example, oxygen reacts with the double bond 

 of an unsaturated acid to form an ethylene oxide linkage. In the case 

 of a polyunsaturated acid, such as linolenic, the addition of oxygen 

 to the double bonds results in the production of a resinous compound. 

 Fats containing large quantities of such polyunsaturated acids are 

 important to the paint and varnish industry, where the formation of 

 a tough resinous film is desirable in the drying of these products. 

 Linseed and tung fats are examples of natural pioducts used in the 

 paint industry. 



Reactions 



Althotigh fatty acids enter into all the reactions customarily ex- 

 pected of the funtional groups which they contain, few of these 

 merit discussion in this book. Those that do are hydrogenation and 

 reduction, soap production, and esterification. 



