182 PROCEEDINGS OP THE AMERICAN ACADEMY 



who showed that pyromucic acid was not attacked by hydroxylamine, 

 and of Wagnei',* who failed to reduce the furfuran oxygen with zinc 

 ethyl. Of the known forms in v/hich oxygen occurs, therefore, there 

 remains only the oxide form, C-O-C, which can be assumed to exist 

 in the molecule of pyromucic acid. Moreover, Baeyer t has shown by 

 the conversion of furfurol into furfuracrylic, furfurpropionic, furonic, 

 and pimelic acids that the carboxyl group of the pyromucic acid is 

 attached directly to one of these two carbon atoms which bear the 

 oxygen atom. 



In accordance with these facts, Baeyer has proposed the following 

 three formulae for pyromucic acid, the first of which he suggested in 

 1870,$ the other two in 1877 §: — 



Of these three formuke, however, Baeyer preferred the second, since 

 li, appeared to explain most readily the formation from pyromucic acid 

 of derivatives of fumaric acid which Limpricht had observed. 



Since pyromucic acid forms an addition product containing four 

 atoms of bromine, to this tetrabromide must be assigned in any case 

 one and the same formula. 



Br Br 



HC-C-COOH 



\ 

 O 



/ 



HC - CH 

 Br Br 



The simultaneous formation from this tetrabromide of two dibrom- 

 pyromucic acids, which we have observed, one of which can be con- 

 verted by oxidation into raonobromfii marie (or monobrominaleic) acid, 

 the second into dibrommaleic (or mucobromic) acid, seems to us to 

 necessitate the rejection of the second formula. From the pyromucic 



* Ber. dor deutsch. ohem. Gesell., xvii. 1067. 



t Ibid., X. 1358. % Ibid., iii. 517. § Ibid., x. llWl. 



