Pathways of Decomposition of Indole Derivatives 193 



multiple pH chromatograms results from tautomerization at high pH 

 values (22). 



The two aldehydic compounds investigated in this study, lAAL 

 and lA, produce in chromatography unusually large spots (Figures 

 5 and 6). Thanks to the properties of double chromatograms (27) 

 those spots can be interpreted in terms of different states of polymeri- 

 zation of these compounds. Spontaneous precipitation occurring in 

 aged solutions of lAAL and lA may also result from polymerization 

 which probably occurs through the side-chain as in the corresponding 

 aliphatic aldehydes. Solutions of lAA (0.1 per cent) in boiled (air- 

 free) water exposed to ultraviolet radiation do not produce the brown 

 discoloration of ordinary solutions but instead become milky. This 

 also may be due to polymerization of which there is evidence in 

 double chromatograms (Figure 7). It is seen that the spot in the 

 upper right-hand corner is in reality quadruple and composed of 

 two primary spots IX and X on the diagonal and two secondary 

 spots, one of them a spot of IX produced from the substance of spot 

 X and the other one, a spot of X, produced from the substance of 

 spot XI. The best interpretation of this composite spot seems to 

 be that IX is a polymer of X (I A A). 



In Table 1 is shown the number of spots and zones of decompo- 

 sition products of indole derivatives in chromatograms and ionograms 

 which exhibited the properties just described. The derivatives them- 

 selves are included in the number whenever they possessed the cor- 

 respondnig property. 



DISCUSSION 



The most significant result of these studies is perhaps the small 

 number of spots and zones of our chromatograms and ionograms that 

 give the Salkowski and the Gordon-Weber reactions. Only in the case 

 of TRPH, IPA, and lAA was it possible to demonstrate the presence 

 of the immediate product of degradation of the side-chain, IPA, 

 lAAL and IGCA, respectively. The demonstration of IGXA in the 

 case of IGCA and of lA in that of IGXA was doubtful. The prod- 

 ucts of more advanced degradation of the side-chain are even more 

 rare, and only lAA, among the decomposition products of TRPH 

 and, with IGCA, among those of IPA, is detectable in some of our 

 chromatograms. The identification of lA in the chromatograms of 

 TRPH, IPA, lAAL and IGXA is doubtful in view of the possible 

 confusion with o-aminobenzene derivatives with the same Rf. It 

 seems, therefore, that degradation of the side-chain is not a major 

 pathway in the spontaneous decomposition (aging) or the decomposi- 

 tion induced by ultraviolet radiation- of the indole derivatives. 



