CHEMICAL PROPERTIES OF FATTY ACIDS AXD RELATED COMPOUNDS 139 



V V 



^0— H-N^ /0-H— N,^ 



R~Cv /'C~R R^Ca. /C^R 



I I 



H H 



C'yclic pol.\-iner struoture of amides 



The cyclic dimers may form larger polymers through fusion. 



Of the many other series of amides and related compounds, several are of 

 interest to the fat chemist. For example, the amides of a number of un- 

 saturated fatty acids have been shown to be solids. Oleamide melts^*^^ at 

 75-76 °C., elaidamide at 93-94 °C., eiucamide at 82.5-83 °C., and brassid- 

 amide at 94 "C.^"* The amides of the dibasic acids deserve attention. 

 There are two series of such amides, depending upon whether one or two 

 amide groups are present. The monoamides have considerably lower melt- 

 ing points than do the diamides. Thus, the corresponding melting 'points 

 in °C. for the two types are as follows: adipic acid, monoamide,^"^ 125- 

 130, diamide^io-^'S 220; suberic acid,^"^ monoamide, 125-127, diamide, 

 216; azelaic acid,*"^ monoamide, 93-95, diamide, 175-176; and sebacic 

 acid,^"^ monoamide, 170, diamide, 210. 



The amides show considerable irregularity in solubility, which in some 

 cases seems to be a random distribution. The discrepancies are difficult to 

 explain, but may be related to polymer formation. The aliphatic amides 

 do not dissolve in water but in the organic solvents. In fact, the higher 

 amides are so hydrophobic that they are used in various waterproofing 

 preparations. Ralston, Hoerr, and PooP^^ reported variations from the 

 normal in benzene, ethyl acetate, and 2-butanone. Lauramide was found 

 to be more soluble than capramide, while palmitamide dissolved to a greater 

 extent than did myristamide. The monoamides of the dicarboxylic acids 

 are water-soluble, while the diamides are also slightly so. 



The aliphatic amides are essentially neutral substances, since the basic 

 effect of the amino group is compensated by the acidic reaction of the acyl 

 portion of the molecule. Although the amides are relatively stable com- 

 pounds, they can be hydrolyzed to ammonia and their parent fatty acid 

 when heated with hydrochloric acid or sodium hydroxide. The reaction is 

 especially responsive to heat, and it occurs at a rate which decreases with 

 the lengthening of the chain. Strenuous measures must be employed to 

 bring about hydrolysis of the high molecular weight amides. Alkaline hy- 



«<" O. Aschan, Ber., 31, 2344-2350 (1898). 



608 Y. Toyama, /. Soc. Chem. Irul. Japan, 25, 1053-1055 (1922); Chem. AbsL, 17, 3161 

 (1923); cited by A. W. Ralston, Fattxj Acids and Their Derivatives, Wiley, New York, 

 1948, p. 594. 



509 L. Etaix, Ann. chim. [7], 9, 356-409 (1896). 



610 L. Henry, /. Chem. Soc, 48, 886-887 (1885). 



"1 L. Henry, Cotnpt. rend., 100, 943-946 (1885). 



"2 A. W. Ralston, C. W. Hoerr, and W. O. Pool, J. Org. Chem., 8, 473-488 (1943). 



