92 III. OXIDATION AND METABOLISM 



(a) a,l3-Dehydrogenation. Quagliariello^"-^^ advanced the hypothesis that 

 Q!,(8-dehydrogenation accompanies or precedes the /^-oxidation of fatty 

 acids. Thus, a typical fatty acid would be dehydrogenated as follows:^ 



/3 a -2H a 



CH3(CH2)„-CH2CH2-COOH > CH3(CH2).CH:CH-COOH 



This reaction would be analogous to the conversion of succinic acid to fu- 

 marie acid. 



;8 a -2H /3 a 



HOOCCH2-CH2COOH > HOOCCH:CHCOOH 



Succinic acid Fumaric acid 



However, although the dehydrogenation of succinic acid occurs readily in 

 tissues, the corresponding reaction to the Q:,(8-unsaturated acid,^^ aconitic 

 acid, does not occur in the case of tricarballylic acid, although QuasteP^ 

 was able to demonstrate some dehydrogenation of tricarballylic acid by 

 Bacillus (Escherichia) coli. 



a'. Detection of Q;,/3-Unsaturated Acids: The occurrence of Q:,/3-unsat- 

 urated acids can be proved by virtue of the fact that they react with di-(2?- 

 dimethylaminophenyl)-ureide to form characteristic yellow ureides;^'* on 

 the other hand, saturated fatty acids form colorless ureides. This reaction 

 has been employed successfully by Breusch and Ulusoy^^ for the determina- 

 tion of Q!,|(3-misaturated fatty acids in fats. Even oily fatty acids can be 

 precipitated as crystalline ureides from an ether solution. The reaction is 

 as follows : 



CH.r(CH2)„CH:CHC00H + 



N— C6H4— N(CH3)2 



N— C6H4— N(CH3)2 

 a,;8-Unsaturated acid Di-(p-dimcthylaminophenyl)-ureide 



O 



II 

 CH3 • (CHOn • CH : CHC— N— C6H4— N(CH3 h 



I 



c=o 



HN— C6H4— N(CH3)2 

 Crystalline Yellow Ureide 



The Reaction Involved in the Separation of a,/3-unsaturated fatty Acids from a Fatty 

 Acid Mixture with di-(p-dimethylaminophenyl)-Ureide, According to the Method of 

 Zetzsche et al.^^ 



^^ G. Quagliariello, Atti accad. nazl. Lincei, Classe sci. fis. mat. e nat. [6], 16, 387-389, 

 552-554 (1932). 



" G. Quagliariello, Angew. Chem., 47, 370 (1934). 



