128 MOLECULAR STRUCTURE 



liquid only slowly and with transformation into the other ; 

 on treatment with acid and shaking out with ether the 

 enol-form is recovered. It may be added that the two 

 formulae might be confirmed by the fact that the first 

 compound should exist in two isomeric states, like fumaric 

 and maleic acids : 



HCOH HOCH 



II and r || 



C 6 H 5 CCO 2 C 2 H 5 C 6 H 5 CC0 2 C 2 H 5 , 



while the second, containing an asymmetric carbon atom, 

 should split into two optical antipodes. 



As a second item towards the explanation of the be- 

 haviour of tautomeric compounds, Klister's 1 proof should 

 be mentioned that a mixture in chemical equilibrium can 

 actually be obtained by means of partial transformation. 

 The body considered was hexachlorketopentane, C 5 C1 6 O, 

 which is obtainable in two isomers, distinguished as /3- and 

 y-compounds, with the probable constitutional formulae : 



and 



Actually the /3-compound is distinguished by forming with 

 aniline in alcoholic solution a slightly soluble anilide, 

 which is made use of to determine the proportions of the 

 mixture. 



On heating, each isomer suffers a transformation leading 

 to a mixture in chemical equilibrium that shows all the 

 characteristics of a tautomeric compound. The formation 

 of this mixture was followed out at 210-5. Measured 

 amounts of /3-pentane were heated for a measured time (), 

 and after sudden cooling the fraction (x) converted into 



1 Zeitschr.f. Phys. Chem. 18. 161. 



