174 III. CHEMISTRY OF NEUTRAL FATS 



The following simple and mixed triglycerides would be possible where 

 only two fatty acids (such as palmitic and stearic) are available: 



1. tripalmitin 



2. a-stearyl-a',/8-dipalmitin 



3. /3-stearyl-a,Q;'-dipalmitin 



4. a'-stearyl-Q!,/3-dipalm4tin 



5. a-palmityl-a',/3-distearin 



6. j3-palmityl-a,a'-distearin 



7. a'-palinityl-a,/3-distearin 



8. tristearin 



However, since the positions a and a' are equivalent, 2 and 4 as well as 5 

 and 7 are identical; this leaves the remaining 6 (1, 2, 3, 5, 6, and 8) as the 

 different possible compounds. 



(a) Symmetrical Mixed Triglycerides. The Fischer method,^ employing 

 alival, which is useful for the production of symmetrical diglycerides, can 

 be used to produce symmetrical mixed triglycerides. It is only necessary 

 to treat the diglyceride with the acyl chloride as indicated in the accom- 

 panying equation. The method of Griin and associates, ^"•"^^-^^ who used 



HzCOOCR HzCOOCR 



.J_.. R'COCI I / 



HCOH ►HCOCCR 



I I 



HzCOGCR HzCOOCR 



1,3-Diacylglyceiol Syniiiietrical 



mixed triglyceride 



symmetrical diglycerides prepared from glycerol disulfuric acid for acyla- 

 tion, is described below. 



HjCOH HjCOSOjH 



I 



HCOH "g^°^ - HCOH ^^^ 



I 

 HzCOH HsCGSGjH 



Glycerol 1,3-Glycerol di- HsCOOCR HXOOCR 



sulfuric acid ^[^^ ^^^ HCOOCR' 



I I 



HjCOOCR HsCGOCR 



1 ,o-Diacyl- Symmetrical 



glycerol mixed triglyceride 



(6) Unsymmcirical Mixed Triglycerides. The most satisfactory method 

 for the preparation of the unsymmetrical triglycerides is by the acylation 



HjCOH HjCGGCr' 



H^oH -I^ii^i^-^ HCGGCR' 



I I 



H2COGCR HzCGOCR 



l-Acylglj-cerol Unsymmetrical 



mixed triglyceride 



of the a-monoglyceride." The Fischer method given above has been sat- 

 " J. C. Irvine, J. McDonald, and C. W. Soutar, /. Chem. Soc, 107, 337-351 (1915). 



