138 



II. CHEMISTRY OF FATTY ACIDS AND GLYCEROL 



shown to have melting points which are strikingly similar to those of the 

 corresponding fatty acids. ^"^ These values are included in Table 47. 



Table 47 

 Melting Points of Amides, Anilides, and iV-METHYL Amides of Saturated Acids" 



" Adapted from A. W. Ralston, Fatty Acids and Their Derivatives, Wiley, 1948, p. 593. 

 ^ Freezing points. 



It seems probable that the amides may exist in either of two forms, i.e., 

 the keto or the enol form, which are in equilibrium. 



RC-NHa^ 



/OH 

 :RC=NH 



Keto 



Eiiol 



The irregularities in properties are believed to be ascribable to some form 

 of molecular association. The aberrant results are chiefly observed in the 

 lower members of the series, and the discrepancies are reduced by the in- 

 troduction of a phenyl group in the molecule. ^°^ Anilides have less ten- 

 dency to form association compounds than do the corresponding amides. 



It is believed that the association of amides results in the formation of 

 either linear or cyclic polymers. On the basis of the hydrogen-bonding 

 characteristics of the amides, Copley el aL^"" have suggested the following 

 stnictures for these polymers: 



R R 



C V X 



H I H 



R 



Linear polymer of amides 



50^ G. F. D'Alelio and E. E. Reid, J. Am. Chem. Soc, 5.9, 109-111 (1937). 

 «« A. N. Meldrum and W. E. S. Turner, /. Am. Chem. Soc, 97, 1605-1616 (1910). 

 *"« M. J. Copley, G. F. Zellhoefer, and C. S. Marvel, /. Am. Chem. Soc, 60, 2666-2673 

 (1938). 



