SYNTHESIS OF THE GLYCERIDES 167 



are possible. The simple triglycerides us,ually carry the name of the 

 component acid with a prefix of tri and a suffix of ein replacing the terminal 

 ic. In the case of the mono- or diglycerides, the same suffix is used with the 

 appropriate mono or di preceding the name of the acid. With mixed tri- 

 glycerides containing two molecules of one acid, the prefix di and the sufiLx 

 ein are given to this acid, while the name of the single acid precedes, with a 

 suffix yl replacing the terminal ic of the acid. Another method of ter- 

 minology employs the suffix yl for both constituents and ends the name with 

 the term glycerol. Still another modification involves numbering the glyc- 

 erol carbons 1,2,3 instead of a,l3,a'. Thus, the following names may cor- 

 rectly be applied to the following mixed triglyceride : 



HjC— OCO(CH2)i6CH3 



I 



HC— OCO(CH2):oCH3 



I 

 HjC— OCO(CH2)i6CH3 



/3-lauryl-Q;,Q:'-distearin, 2-lauryl-l,3-distearin, 2-laurodistearin, or /3-lauryl- 

 a,Q;'-distearjdglycerol. The glycerides are frequently referred to without 

 letter or number designation as "symmetrical" or "unsymmetrical." The 

 above compound could be called symmetrical lauryl-distearin. In the case 

 of the diglyceride, a:,Q!'-dipalmitin, the term symmetrical dipalmitin may 

 be used, while the a-/3-isomer would obviously be knowTi as unsymmetrical 

 dipalmitin. 



3. Synthesis of the Glycerides 



(1) Monoglycerides 



The monogl3''cerides have assumed considerable importance because of 

 their use in the preparation of the so-called "high ratio" shortenings. 

 The two series of compounds, a and ^, require different methods for sjai- 

 thesis. 



a. a-Monoglycerides. The classical method for the synthesis of 

 a-monoglycerides was developed by Emil Fischer, 2- ' although Berthelot^ 

 had, many years earlier, prepared a monostearin by heating an excess of 

 glycerol with stearic acid in a sealed tube at 200°C. However, since this 

 method also yielded di- and triglycerides with longer periods of heating, it 

 is evident that the product obtained was probably impure. 



Fischer's method involves the condensation of glycerol with acetone to 

 give l,2-isoprop)''lideneglycerol (acetoneglycerol), which is subsequently 

 esterified with an acyl chloride in the presence of cold quinoline. The 



2 E. Fischer, Ber., 53, 1621-1633 (1920). 



» E. Fischer, M. Bergmann, and E. Barwind, Ber., 53, 1589-1605 (1920). 

 * M. Berthelot, Chimie organique fondee siir la synthese, Vol. 2, 1860. Cited by B. F. 

 Daubert and C. G. Iving, Chem. Revs., 29,211 (1941). 



