48 



Proceedings of the Royal Irish Academy. 



H 

 HC = C 



1 >o = 



HC = C 



Tetraphenol. 



H 



COOH 

 1 





HC = C 

 EC = C 



Pp'omucic acid, 



H 



COOH 



1 



1 



HC = C 



1 >o = 



HC = C' 



Dehydromucic ( 



COOH 





If we now, employing Baeyer's fonnula for pyrrol, write tlie three 

 ethyl derivatives, on the view stated above, the relation between theni 

 and the tetraphenol derivatives is at once apparent : 



H 

 HC = C 



I -^T^ (CHs) = Ethyl-pyrrol. 

 HC = C 



H 



COIs^H (C0H5) 



I 

 HC-C 



^IS" (C0H5) = Diethyl-carbo-pyiTol-amide. 

 HC = C 

 H 

 CONH (C2H5) 



HC = C 



^jS" (C2H5) = Triethyl-carbo-pyrrol-amide. 



HC = C 



CONHCC^Hs) 



We have now got the clue to the mechanism of the reactions by 

 which these bodies are obtained from mucic acid. Crum-Brown and 

 Limpricht have both obtained from mucic acid bodies whose formation 

 can only be accounted for on the hypothesis that it (mucic acid) is a 

 derivative of normal adipic acid, the oxidation product of normal 

 }iexane, Ce Hu. It must then have the constitution — 



