CHEMICAL PROPERTIES OF FATTY ACIDS AND RELATED COMPOUNDS 123 



physical adsorption rather than in ester linkage. ^^^-^^^ Since the so-called 

 fat-by-hydrolysis represented lipid material in starch which could not be re- 

 moved by ether or carbon tetrachloride extraction, it was formerly believed 

 to be present in ester linkage. Schoch,^^^ however, found that the fat could 

 be removed almost completely by methanol, 80% dioxane, or other hydro- 

 philic fat solvents. This investigator also demonstrated that it was pos- 

 sible to reintroduce fatty acids into defatted starches by treatment with 

 fatty acid solutions; these reintroduced fatty acids were as tightly bound 

 as the true fat-by-hydrolysis. Since it has recently been shown that the 

 presence of fatty acids interferes with the amylose-iodine complex, ''^^ it is 

 believed that the fatty acid-amylose reaction is similar to that of the iodine- 

 amylose combination. Mikus et al.'^" have suggested that the fatty acid 

 retention is not due to a surface phenomenon but rather to a retention in 

 holes of the helices in the amylose structure. 



Melting points of the palmitate esters of the polyhydric alcohols are in- 

 cluded in Table 44. A description of cholesterol esters is included in Chap- 

 ter IV, while a discussion of xanthophyll and other carotenol esters is given 

 in Chapter VI. 



c. Formation and Preparation of Compounds Related to Fatty Acids 

 but Having Modifications of Carboxyl Group. Some of the changes in 

 the carboxyl group are so minor that the resulting compounds still possess 

 many of the properties associated with the lipids. Thus, the reduction of 

 fatty acids to aldehydes or even to alcohols yields a series of compounds 

 which possess fat-like properties. In many cases these substances are found 

 in nature. The corresponding hydrocarbons in which a complete removal 

 of the oxygen of the fatty acid has occurred are sometimes present in the 

 case of neutral fats, and are, in fact, rather important natural products. 

 The acid anhydrides, likewise, differ little from the fatty acids, and readily 

 revert to them. The amides lack many of the lipid properties, but are of 

 interest because of their widespread distribution in both the plant and the 

 animal kingdoms. The nitriles and acid chlorides are very important 

 derivatives of fatty acids which are of particular interest because of the 

 many reactions into which they enter. Each of these derivatives will be 

 considered in turn and their relationship to fatty acid reviewed. Several 

 other equally important derivatives, such as the amines, the ethers, the 

 sulfur-containing compounds, and the ketones differ sufficiently from the 

 fatty acids to justify their omission here. A discussion of these compounds 

 is to be found in Ralston.^ 



^" L. Lehrman, /. Am. Chem. Soc, 64, 2144-2146 (1942). 

 *^* R. L. Whistler and G. Ililbert, /. Am. Chem. Soc, 66, 1721-1722 (1944). 

 ••15 T. J. Schoch, /. Am. Chem. Soc, 60, 2824-2825 (1938). 

 ^16 T. J. Schoch and C. B. Williams, ./. Am. Chem. Soc, 66, 1232-1233 (1944). 

 ^" F. F. Mikus, R. M. Hixon, and R. E. Rundle, J. Am. Chem. Soc, 68, 1115-1123 

 (1946). 



