220 PROCEEDINGS OF THE AMERICAN ACADEMY 



made, that the constitution of mucobromic acid was probably repre 

 sented by the formula, — 



CBr^ = CH — CO — COOH 



In 1879, Toennies,* in investigating the action of bromine upon 

 dibrompyroraucic acid f in Baeyer's laboratory, found that a sub- 

 stance, C4H2Br202, was formed according to the equation, — 



C,R,Bv,0, + Br^ + H^O = C.H^Br^O^ + CO^ + 2HBr, 



and that this could readily be converted into mucobromic by oxidation. 

 This mode of formation led Toennies to the conclusion that muco- 

 bromic acid was the half-aldehyde of dibromfumaric acid. Further 

 investigation in this direction Toennies relinquished in order to avoid 

 interference with my work. 



At the time of the publication of this paper by Toennies, my own 

 experiments had shown that this view was in part correct. The 

 conversion of mucobromic acid by the action of argentic oxide or 

 other oxidizing agents into the dibrommaleic acid of Kekule showed 

 with sufficient precision that it was the half-aldehyde of this acid. On 

 the other hand, it was evident that the dibrommaleic acid itself did 

 not belong to the fumaric series, as could fairly be inferred from its 

 mode of preparation ; but that it was in reality a substituted maleic 

 acid, since it could be carried unchanged through its anhydride. 



A more direct proof of this fact was furnished by the discovery by 

 Bandrowski J of an isomeric acid of higher melting point, which could 

 be converted into this by distillation. 



Although it cannot be said that the constitution of fumaric and 

 maleic acids is definitely established, the brilliant researches recently 

 published from Fittig's laboratory leave but little doubt that the 

 formula of maleic acid is, — 



CK, — COOH 

 I 



= c — coon 



If this view of its structure be adopted, the structure of mucobromic 

 acid must be represented by one of the formulte, — 



* Berichte der deutsch. chem. Gesellsch., xii. 1202. 

 t Ibid., xi. 1Q88. 

 } Ibid., xii. 1232. 



I 



