1914^] Organic Compounds 87 



represented hy formula in which the carbon atoms are united 

 hj double or triple bonds. 



Wm. J. Hale explains color as being due in both aromatic 

 and aliphatic compounds to the oscillations of the bonds within 

 the molecule and this he calls isorropesis. His theory is that a 

 change in linkage produces the absorption bands. This he 

 illustrates by diacetyl in which the make and break may be 

 shown thus : 



CH3-C-C-CH3 CHs-C^C-CHs 



II II ^ II 



00 0-0 



The make and break contact between the oxygen atoms would 

 give marked activity to these atoms. The color in quinoid 

 compounds is due to isorrepsis in this manner : 



O 



II 



c c 



/ \ /l\ 



HC CH HC CH 



II II II I I 



HC CH HC O CH 



\ / w// 



c c 



II 

 o 



Isorropesis occurs between adjacent carbon atoms possessing 

 residual affinity and the para carbon atoms are considered as 

 possessing the relationship as indicated by their chemical be- 

 havior which is as if the atoms lay next each other. Isorropesis 

 need not always occur between oxygen atoms possessing residual 

 affinity but other atoms may show similar reactions. For ex- 

 ample the nitranilines, H2N-C6H4-Isr02, given an absorption 

 curve similar to that of para-benzoquinone. Here the residual 

 affinities of the N atoms are disturbed by the motion of the 

 benzene molecule. In compounds of the benzene structure, 

 the cause of the color begins with the vibration of the molecule 

 itself. 



The presence of other groups may augment or retard the 

 influence of unsaturated atoms undergoing isorropesis and con- 

 sequently the corresponding variations in the oscillation fre- 

 quency will be indicated by similar variation in the nature of 



