422 The Philippine Journal of Science 1913 



ring until the period between them has reached a point where 

 separation takes place. The band due to a disubstituted benzene 

 ring appears in its characteristic position, while the original 

 absorption shifts in the opposite direction toward the red. The 

 results of this new condition within the molecule are frequently 

 evident to the eye either by the production of color or through 

 fluorescence. 



A similar effect may be produced by increasing the residual 

 affinity of the side chain through the actual substitution of 

 active groups. Thus benzylidene phthalide (fig. 8), cyanbenzyl- 

 idene phthalide (fig. 9), phthalylacetic acid (fig. 10), and di- 

 phthalyl (fig. 11) all contain such unsaturated centers, and give 

 absorption spectra characterized by two bands even in alcohol 

 solution. The action of sulphuric acid on these compounds is 

 less marked, but entirely analogous. The less refrangible band 

 is shifted toward the red, while the second approaches the shorter 

 wave lengths characteristic of disubstituted benzene absorption. 



Phthalophenone in alcohol shows a single band (fig. 13) similar 

 to the simple phthalide from which it is derived. The effect of 

 replacing two hydrogen atoms by two phenyl groups does not 

 greatly alter the equilibrium. A slight shift of the band toward 

 the red and a decrease in its persistence mark the change. The 

 solution in sulphuric acid, however, is decidedly altered. As 

 before, the single original band is divided, the result being a less 

 refrangible band accompanied by disubstituted benzene absorp- 

 tion. A very strong band of great width and persistence also 



appears at — = 2220 in the color region. Oxydiphenyl phthalide 



A 



and phenolphthalein have been shown to give a similar band in 

 this solvent, 23 but the authors do not comment on the spectra. 



The change from a colorless solution to a colored one, or an 

 alteration in the existing color in compounds of the type studied 

 in this paper, cannot be explained logically by the quinoid theory. 

 In many cases such a change in structure is impossible. It is not 

 probable that phthalophenone assumes a true quinoid form when 

 dissolved in concentrated sulphuric acid. A more reasonable 

 explanation may be found in assuming a conjugation between 

 latent valencies of the unsaturated phenyl and carbonyl groups 

 similar to that suggested for the alkali salts of phthaloxime. 24 

 In this case, the increased energy is supplied by the solvent 



a Meyer und Fischer, Ber. d. deutsch. chem. Ges. (1913), 46, 80. 

 M Pratt and Gibbs, This Journal, Sec. A (1913), 8, 165. 



