424 The Philippine Journal of Science 1913 



Nitrosophthalimidene also typifies a condition of high activity 

 in the side chain, and its absorption spectrum in alcohol contains 

 three bands, one of which is in the color region (fig. 7). The 

 introduction of the unsaturated nitroso group replacing the imido 

 hydrogen has augmented the residual activity of the molecule and 

 has also provided the condition necessary for conjugation. The 

 complete structural formula corresponding to the absorption 

 spectrum may be represented as : 



CeH 



^H 2 /H 



CT (X 



<^ \n-no f=^ c 6 h 4 <^ ^n=no 



^0 -0__ H(M) 



containing a six-membered conjugated ring. The equilibrium is 

 shifted to the right by alkalies with salt formation. 



The absorption spectra of the compounds studied in which 

 nitrogen has replaced an atom of oxygen in the side chain are 

 especially interesting, but still more difficult to explain. Phthal- 

 imide (fig. 5) and phthalanil (fig. 12) give very similar absorp- 

 tion in ordinary solvents. The bands are shifted toward the 

 longer wave lengths about equal distances in sulphuric acid solu- 

 tion, but the persistence of the band of the former compound is 

 very greatly increased while that of the latter is only slightly 

 greater. The appearance of a benzene absorption band is not 

 evident in either compound in sulphuric acid. Phthalimidine 

 (fig. 6) more closely resembles the phthalic acid type, although 

 even here sulphuric acid does not result in the production of a 

 new absorption band. 



Phthalophenone anilide (fig. 14) shows much less pronounced 

 selective absorption than phthalophenone. The sulphuric acid 

 solution of the former still gives a color band heading at the 

 same place as that of the latter, but it appears at very much 

 greater concentration and is only about half as persistent. 



The absorption spectrum of phthaloxime is not greatly altered 

 by using sulphuric acid as a solvent, and no new bands are 

 produced. 



In every case the introduction of nitrogen in place of oxygen 

 has decreased the effect caused by sulphuric acid. This may be 

 explained readily if the theory regarding the action of sulphuric 

 acid on the phthalids be accepted. The natural affinity between 



