184 PROCEEDINGS OF THE AMERICAN ACADEMY 



explanation of the formation of derivatives of fumaric or maleic acid 

 by oxidation somewhat difficult (the same objection applies, of course, 

 to a still greater degree to the third formula); and still we cannot con- 

 sider this objection a serious one, while the normal behavior of sub- 

 stances containing the group C=C-C=C is not established, and the ease 

 with which molecular rearrangements take place in non-saturated com- 

 pounds is so well known. Until the structure of fumaric and maleic 

 acids is more definitely established, it would be useless to attempt any 

 discussion of the significance of the fact which we have established, 

 that maleic acid and its derivatives, and not the corresponding deriva- 

 tives of fumaric acid, are the first products formed in the decomposition 

 of the substituted pyromucic acids. 



If the carbon atoms in pyromucic acid are designated as usual, be- 

 ginning with the carboxyl group, 



/8 a 

 HC=C-COOH 

 \ 



O 

 /. 

 HC = CH 



y 8 



the constitution of the two isomeric dibrompyromucic acids may be 

 expressed by the names which we have given to them, the /3y-dibrom- 

 pyromucic acid (melting-point 191-192'^), j^assing by oxidation into 

 dibrommaleic acid, while the /38-dibrompyromucic acid yields mono- 

 brommaleic acid. 



The determination of the constitution of tlie monobrompyromucic 

 acids is a matter of no difficulty. The oxidation of the monobrom- 

 pyromucic acid melting at 183-184° directly to maleic or fumaric acid 

 shows that its bromine must be in the 8-position, and its foi'mula, 



HC = C-COOH 

 \ 



o 



/ 



HC=CBr 



On the other hand, the monobrompyromucic acid melting at 128- 

 129°, since it is formed by the reduction of either of the two dibrom- 

 pyromucic acids, must have its bromine atom at /?, and its formula is 

 therefore 



