THE FATS 59 



In these compounds the phenomenon of isomerism occurs owing 

 to the presence of primary and secondary alcohol groups in glycerol. 

 In the case of the diglycerides and the triglycerides mixed esters, in 

 which the fatty acid radical varies, are possible : 



(6) (7) 



CH 2 OC . CH 3 CH 2 OH 



CHOH CH OC.CIL, 



CH 2 00 . CH 2 . CH 3 CH 2 - OC . CH 2 CH 3 



(8) 

 CH 2 OC.CH 3 



CH OC.CH 2 .CH 3 



CH 2 OC . CH 2 . CH 2 . CH 3 



The glyceryl esters which compose the fatty material of living 

 matter whether animal or plant are mainly triglycerides, the 

 monoglycerides and diglycerides being seldom found in nature. The 

 natural fat is usually found to consist of a mixture of triglycerides ; 

 these triglycerides, instead of being mixed esters as in formula (8), are 

 generally simple esters as in formula (5). The differences in the composi- 

 tion of the natural fats depend therefore on the variety of the fatty 

 acid radical combined with the glycerol. 



The fatty acids which enter into the composition of the tri- 

 glycerides belong to two main homologous series : 



A. The saturated fatty acids, namely : 

 Formic acid, H.COOH 

 Acetic acid, CH 3 .COOH 

 Propionic acid, CH 3 . CH 2 . COOH 

 Butyric acid, CH 3 .CH 2 .CH 2 .COOH 

 Valerianic acid, CH 3 .(CH 2 ) 3 .COOH 

 Caproic acid, CH 3 .(CH 2 ) 4 .COOH 

 Caprylic acid, CH 3 . (CH 2 ) 6 . COOH 

 Capric acid, CH 3 (CH 2 ) 8 .COOH 

 Laurie acid, CH 3 (CH 2 ) 10 . COOH 

 Myristic acid, CH 3 (CH 2 ) 12 . COOH 

 Palmitic acid, CH 3 (CH 2 ) 14 .COOH 

 Stearic acid, CH 3 (CH 2 ) 16 . COOH 

 Arachidic acid, CH 3 (CH 2 ) 18 .COOH 

 Behenicacid, CH 3 (CH 2 ) 20 .COOH 

 Lignoceric acid, CH 3 (CH 2 ) 22 . COOH 



