ABSORPTION SPECTRA AND CHEMICAL CONSTITUTION. 157 



The present investigation was undertaken with the view of ascertain- 

 ing whether a comparison of the absorption spectra of the two ethers 

 with the absorption spectra of o-oxycarbanil would, as in the cases of 

 isatin and carbostyril/ yield results from which the constitution of the 

 parent substance might be inferred. Assuming that one or other of the 

 ethers differs from o-oxycarbanil only in the substitution of the alkyl 

 group for an atom of hydrogen, the constitution of the two substances 

 being otherwise identical, we should expect the absorption spectra of the 

 parent substance and this ether to be practically the same. On the other 

 hand, the ether which differs in constitution from the parent substance 

 should give a different spectrum. Groenvik '^ gives 136-138°, Sandmeyer 

 137°, and Bender 141°, as the melting-point of o-oxycarbanil. Although, 

 apart from this slight difference, there was no reason to doubt the identity 

 of the substances obtained by these chemists, we thought it well to ex- 

 amine specimens prepared independently by two different methods and 

 selected for the purpose, the substances obtained by fusion of o-amino- 

 phenol with urea and by the decomposition of the lactim ether with 

 hydrochloric acid. We found that the two specimens when heated side 

 by side in capillary tubes behaved in exactly the same way, softening at 

 137° and melting completely at 139°-5. Solutions of the two specimens 

 gave identical spectra. 



The spectra of o-oxycarbanil and of the lactam ether are almost iden- 

 tical. The amount of general absorption is practically the same in both, 

 and the spectra of both substances show a well-marked absorption band 

 occupying the same position and persisting, in both cases, through the 

 eame range of dilution. The spectra of the enolic ether, on the other 

 hand, show a smaller amount of general absorption, and the absorption 

 band does not appear until a much greater degree of dilution is reached 

 than is required to bring out the band in the other two substances. The 

 range of the band of the enolic ester is also very small. The above curves 

 drawn from the photographs, show very clearly the relations between 

 the spectra of the various substances. 



The conclusion to which the investigation leads is that o-oxycarbanil 

 has the same structure as the lactam or ketonic ether, or, at all events 

 that the lactam structure very greatly predominates, if the assumption is 

 made that the parent substance in solution is a mixture of two tautomeric 

 forms. It is worthy of note that in the three cases of this kind which 

 have now been examined the parent substance possesses the ketonic or 

 lactam constitution. o-Oxycarbanil, it may be noted, gives no colour 

 reaction with ferric chloride. 



The substances used in this investigation were prepared exactly in 

 accordance with the directions given in the papers already quoted. Two 

 distinct preparations of each substance were made and several series of 

 photographs were taken of the absorption spectra of each preparation. 

 No appreciable difference could be detected in the various photographs of 

 the same substance. This is satisfactory evidence of the identity of the 

 compounds, and also of the purity of these particular preparations. 



• Hartley and Dobbie, Trans. Chew. Soc, 1899, 76, 640. 

 2 Bull Soc. Chim., 1876 [ii.], 25, 177. 



