viii, a, 3 Pratt and Gibbs: Two Phthaloximes 169 



tential possibility of such a change. The oscillation or free 

 period in connection with the reversible transformation of one 

 tautomeric form into another is synchronous with the oscillation 

 of the light waves absorbed. This transformation must be 

 understood to include changes that cannot be graphically repre- 

 sented by fixed structural formulas. These peculiar cases are 

 best indicated according to the partial valency theory developed 

 by Thiele. 13 This assumes that all the affinity of two atoms con- 

 nected by a double bond is not used in holding the atoms together, 

 but that there is a slight excess present in each atom. Thiele 

 designates this excess affinity by dotted lines. Application of 

 this idea to phthaloxime gives a formula that may be expressed 

 thus: 



yC==0 



C6H4 



\C==NOH 



The two sets of partial valencies may be assumed more com- 

 pletely to neutralize each other during one phase of the benzene 

 vibration when the atoms are in closer proximity to each other 

 than during the succeeding phase when they are more widely 

 separated. This varying adjustment of forces in connection 

 with the disturbing influence of the hydroxyl group may be 

 thought of as causing the ultra-violet absorption band of phthal- 

 oxime. The equilibrium is essentially the same in phthalic acid, 

 the esters of phthalic acid, and very similar in phthalimide. All 

 of these compounds may be expressed by analogous formulas. 

 Moreover, they all give absorption spectra showing similar ultra- 

 violet absorption bands. This must be considered as evidence 

 of corresponding structure. The influence of the benzene ring 

 is essential in these cases. 



The application of the partial valency theory to explain the 

 activity of carbonyl groups removes the indefiniteness inherent 

 in the method employed by Stewart and Baly 14 to represent this 

 condition. These authors suggest that nascent carbonyl groups 

 be indicated by printing the oxygen in heavy-faced type, thus 



-c- 



and that this condition is essentially dynamic in nature and 

 

 cannot be successfully represented by structural formulas which 



"Ann. d. Chem. (Liebig) (1899), 306, 87. 

 "Journ. Chem. Soc. London (1906), 89, 497. 



