168 The Philippine Journal of Science ma 



A study of the absorption spectra of these and related com- 

 pounds was undertaken for the purpose of obtaining an insight 

 into their molecular arrangement and behavior and evidence 

 regarding the production of color in their salts. 



If the isomerism between the white and yellow phthaloximes 

 is correctly indicated by the above formulas, Ha and lib, it is 

 evident that their absorption spectra must be very closely related. 

 Macbeth, Stewart, and Wright 9 have studied the action of light 

 on unsaturated centers in a molecule, and state that no great 

 change takes place in the general absorptive power of a molecule 

 when such a center is shifted in space with respect to a saturated 

 radical. The carbonyl group in phthaloxime represents the point 

 of maximum unsaturation, while the hydroxyl can hardly be 

 looked upon as the center of much residual affinity. Any relative 

 change in space between carbonyl and hydroxyl should produce a 

 slight modification in the absorption spectrum, but the type would 

 remain the same. Hartley 10 has shown that the stereoisomeric 

 benzaldoximes have the same absorption spectra which show a 

 broad band in the benzene region. 



Hantzsch 13 - has examined several isomeric oximes and states 

 that the absorption spectra of a and y benzyl oximes, the two 

 para nitrobenzaldoximes, and of the chlortoluquinonoximes show 

 great similarity in each case between the two isomers. The syn 

 series absorbs somewhat more strongly than the anti, as might 

 be expected from the greater proximity and consequent mutual 

 influence of the two radicals. Wilson and Heilbron 12 have re- 

 cently prepared two semicarbazones of mesityl oxide, and find 

 corresponding differences due to nitrogen stereoisomerism. 

 Since these characteristics are manifested in the case under 

 discussion, it thus appears that the yellow phthaloxime should be 

 designated as si/w-phthaloxime and the white isomer as anti- 

 phthaloxime as represented by formulas Ha and lib. 



Prior workers have pointed out that absorption bands are not 

 to be attributed to any definite molecular structure, but rather 

 to the existence of dynamic compounds which are not necessarily 

 capable of isolation. The presence of an absorption band is due 

 to intramolecular change from one modification to another, and 

 is expressed by an actual change of linking, or is due to the po- 



' Journ. Chem. Soc. London (1912), 101, 599. 

 "Ibid. (1900), 77, 509. 



11 Ber. d. deutschen chem. Ges. (1910), 43, 1651. 



12 Journ. Chem. Soc. London (1913), 103, 377. 



