SAPONIFIABLE LIPIDS 



71 



Additional fatty acids which are limited in their occurrence will be mentioned where ap- 

 propriate in the following sections of this chapter. 



Name 



Laurie 



Myristic 



Palmitic 



Stearic 



Arachidic 



Behenic 



Lignoceric 



Palmitoleic 



Oleic 



Linoleic 



Linolenic 



Elaeostearic 



Arachidonic 



Erucic 



TABLE 1. SOME COMMON FATTY ACIDS 



Structure 

 CH3(CH2)ioCOOH 

 CH3(CH2)i2COOH 

 CH3(CH2)i4COOH 

 CH3(CH2)i6COOH 

 CH3(CH2)i8COOH 

 CH3(CH2)2oCOOH 

 CH3(CH2)22COOH 

 CH3(CH2)5CH = CH(CH2)7COOH 

 CH3(CH2)7CH = CH(CH2)7COOH 

 CH3(CH2)4CH = CHCH2CH = CH(CH2)7COOH 

 CH3CH2CH = CHCH2CH = CHCH2CH = CH(CH2)7COOH 

 CH3(CH2)3CH = CHCH = CHCH = CH(CH2)7COOH 



CH3(CH2)4CH = CHCH2CH = CHCH2CH = CHCH2CH = CHCH2(CH2)2COOH 

 CH3(CH2)7CH = CH(CH2)iiCOOH 



TRIGLYCERIDES 



Triglycerides are esters of glycerol with three fatty acid molecules: 





 II 



H2COCR 

 ,11 I 



RCOCH 



1? 



H^OCR 



// 



The normal situation is for the three fatty acids to be different and the molecule therefore 

 described as a "mixed triglyceride." Those which are solid at room temperature are 

 called fats, whereas liquid triglycerides are called oils. Most natural fats and oils are 

 not single compounds but mixtures of triglycerides, although one may be predominant. 

 Chemically, fats contain a larger proportion of saturated fatty acids, and oils have more 

 of the unsaturated acids. Oils are further subdivided into drying and non-drying oils. 

 The former are oxidized in the air to form tough films which make them valuable in paints 

 and varnishes. The latter, while they may be oxidized and become rancid, remain liquids. 



