6 



PROCEEDINGS OP THE AMERICAN ACADEMY. 



xc = 



xc = 



C - COOH 



X 

 / 



cx 



xc = 



xc = 



CH 



x o + co 2 

 cx 



This then adds a molecule of haloid acid with the shifting of the double 

 bond in a manner identical with that observed by v. Baeyer and 

 Rupe* in the reduction of dichlormuconic acid : 



XC 



xc 



CH 



x o 



/ 



cx 



+ 



H 



X 



XC - CHo 



x o 



/ 

 XC - CX 9 



The addition product is then decomposed by water, giving the lac- 

 tone. Possibly a molecule of water is directly added to the trisubsti- 

 tuted furfuran, giving 



XC - CH 2 



\ 



XC 



o 

 cx 



OH 



which would at once pass into the lactone by the loss of haloid acid. 



The conversion of the /3y-dibrompyromucic acid into the dibromcro- 

 tonolactone, and of the /3y-dichlorpyromucic acid into the correspond- 

 ing dichlorcrotonolactone by the action of bromine in aqueous solution 

 likewise finds its explanation in the formation of a trisubstituted fur- 

 furan. In aqueous acid or alkaline solution the carboxyl of the sub- 

 stituted pyromucic acids is readily eliminated and replaced by bromine, 

 as was first shown by Hill and Hartshorn f in the case of the 8-brom- 

 pyromucic acid : 



XC = C - COOH 



\ 







} = CH 



XC = CBr 



+ Br 2 = X + C0 2 + HBr 



XC = CH 



By the addition of water the substituted lactone is formed as before. 

 We have shown that the bromanhydrides of mucobromic and muco- 

 chloric acids are also formed in this same reaction. This formation is 

 evidently due to the addition of bromine to the trisubstituted furfuran 

 and the decomposition of this product by water : 



* Ann. Chem. u. Pharm., CCLVI. 25. 



t Berichte d. deutsch. chem. Gesellsch., XVIII. 448. 



