X, A, 1 Gibbs and Brill: Diethylsuccinosvecinate 53 



The existence of mixed crystal forms in ethylsuccinosuccinate 

 and diethylquinonedihydroparacarboxylate was discovered by 

 Lehmann and discussed by Herrmann/^ The possibility of the 

 existence of desmotropic forms and derivatives has been dis- 

 cussed by Hantzsch and Herrmann," 



Hantzsch " refers to the oxidation of ethylsuccinosuccinate 

 as producing quinonedihydroterephthalic ester of the constitution 



H COOEt 

 \/ 

 H-A=0 



0=1 



H COOEt 

 which may indicate that the 3, 6 hydrogen atoms of ethylsuc- 

 cinosuccinate are the first to be oxidized. 



From the work described in this paper we believe that ethyl- 

 succinosuccinate can exist in two forms, the enol and keto, cis 

 and trans modifications being also possible ; it seems reasonable 

 to assume that one of these in the keto compound will favor the 

 migration to the enol form. Of the three forais which Baeyer 

 shows are possible for the enol modification the A^-^ 



COOEt 

 Ha/^— OH 



HOI 



COOEt 

 is the only one tenable when the labile hydrogen atoms are in the 

 1, 4 positions, which from, the evidence at hand, seems to be 

 the case. 



ENOL AND KETO FORMS 



When the mother liquor from which a considerable quantity 

 of ethylsuccinosuccinate has been obtained is concentrated, a 

 small amount of a yellow crystalline precipitate is thrown out. 

 The purification of this compound was effected by crystallizing 

 many times from absolute alcohol. The specimen thus obtained 

 differs from the first precipitate formed in color, melting point, 

 solubility, and absorption spectra and shows some differences 

 in chemical behavior. 



"Ber. d. deutschen ckem. Ges. (1886), 19, 2235. 

 "Ibid. (1887), 20, 2801. 

 "Ibid. (1886), 19, 26. 



