228 III. CHEMISTRY OF NEUTRAL FATS 



to "even" distribution. The proportion of completely saturated triglyc- 

 erides calculated on the basis of "even" and random distribution are 

 70.0% and 65.2%, respectively. The experimentally determined figure for 

 totally saturated triglycerides Avas 67.3%, which could be interpreted as 

 agreeing with either school of thought. 



Another instance in which a pattern of "even" distribution may be con- 

 fused with a random one occurs when the major fatty acids exceed 4 in 

 number. It is only in those fats having a maximum of 3 or 4 fatty acids 

 in major amounts that a clear-cut example of "even" distribution may be 

 observed. In those fats in which 6 or 7 principal acids occur, the calcula- 

 tion of their distribution is approximately similar, whether based upon the 

 principle of "even" distribution or on one of chance arrangement. Hil- 

 ditch and Maddison^^^ have shown that in certain marine oils in which 

 palmitic, hexadecenoic, oleic, eicosenoic, eicosatetraenoic, eicosapentaenoic, 

 docosapentaenoic, and docosahexaenoic acids are present, the distribution 

 of the acids agrees with the "even" scheme; however, the proportions of the 

 several types of glycerides also show a fairly close correspondence to a ran- 

 dom arrangement. Such types of evidence are obviously of little use in 

 giving a satisfactory answer to the problem. 



Another argument in support of the random method of assembling the 

 fatty acids has been based upon the composition of fats synthesized in 

 vitro from a mixture of fatty acids. Bhattacharya and Hilditch^^^ found 

 that, when diglycerides or triglycerides were produced artificially by heat- 

 ing diethylene^ glycol or glycerol at 145°C. under vacuum, in the presence of 

 traces of an aromatic sulfonic acid, with various mixtures of lauric, pal- 

 mitic, stearic, and oleic acids, the acids were arranged in a random manner. 

 Norris and Mattil-^* obtained similar results when interesterification tests 

 were performed. Thus, when soybean oil, cottonseed oil, a mixture of 

 tripalmitin and triolein, or one of lard and hydrogenated lard was heated 

 with a small amount of Sn(0H)2 as a catalyst at 225°C. for short periods, 

 a rearrangement occurred, with the newly formed triglycerides approxima- 

 ting the pattern indicative of chance arrangement. Naudet and Des- 

 nuelle^^* have reported similar data with substrates consisting either of 

 oleodistearin and stearodiolein or of tristearin and triolein. For example, 

 when an equimolecular mixture of tristearin and triolein was so treated, 

 the products obtained at the completion of the reaction consisted of 11.3% 

 of tristearin, 38.6% of oleodistearin, 39.2% of stearodiolein, and 10.9% of 

 triolein. Distribution on a random basis should have resulted in 12.5% of 

 each of the simple triglycerides and 37.5% of each of the mixed triglyc- 

 erides. 



«7 T. P. Hilditch and L. Maddison, /. Soc. Chem. Ind., 67, 253-257 (1948). 



298 F. A. Norris and K. F. Mattil, Oil & Soap, 2S, 289-291 (1946). 



299 M. Naudet and P. Desnuelle, Bull. soc. chim. [5], 14, 323-325 (1947). 



