Pathways of Decomposition of Indole Derivatives 



187 



- O + 



Fig. 4. lonogram of the ultraviolet decomposition products of indole-3-acetic 

 acid. Phosphate buffer 0.1 M, pH 7; 6 hrs., 140 volts. All the colored substances 

 (reddish brown) of the decomposed solution applied at the origin O remained 

 there (zone b). The lonogram was inspected under long-wave ultraviolet light 

 which revealed fluorescent zones a, b', c, and e. Under short-wave ultraviolet light 

 zone f (lAA) was seen as a dark zone due to the quenching of the blue fluorescence 

 of the filter paper. The ionogram was next exposed to ultraviolet radiation 

 through a stencil so that parallel longitudinal exposed bands alternated with 

 unexposed bands. As a result of ultraviolet exposure the blue fluorescence of zone 

 a was markedly intensified, that of zone c decreased and a bright turquoise green 

 fluorescence appeared in zone £. A new zone, d, with strong yellowish fluorescence 

 appeared, in part overlapping zone e. The ionogram was then cut longitudinally 

 in four strips, each of which contained an exposed and an unexposed band. N 

 HCl, Gordon-Weber reagent, and dinitrophenylhydrazine were applied to three 

 of the strips. iV HCl produced a red color in zone d, greatly intensified in the 

 irradiated portion and a pinkish buff coloration in the irradiated portion of zone 

 f. Almost the same colorations were observed in the strip which received the 

 Gordon-Weber reagent which in addition produced a purplish coloration in the 

 unexposed portion of zone £. Dinitrophenylhydrazine produced a brown color 

 in zones a, d, and the exposed portion of f. The color was intensified in the un- 

 exposed portion of a and in the exposed portion of d. Conventional hatching in- 

 dicating approximate fluorescence colors as in Figure 7. 



Sublimation Test 



The production of volatile indole derivatives like skatole and 

 indole in solutions applied to a strip of filter paper and decomposed 

 by exposure of the dry strip to ultraviolet radiation was detected by 

 sublimation onto a clean strip of the same paper. The exposed and 

 the clean strips, separated by a strip of Japanese lens paper, were 

 placed between two glass plates and the whole was set on a hot plate 

 at a temperature of 85° C. for 15 min. The clean sheet was then 

 sprayed with Ehrlich's reagent. 



RESULTS 



Spontaneous and Induced Decomposition 



Judging from the discoloration of their aqueous solutions, several 

 of the indole derivatives of this study decompose spontaneously in a 

 few minutes, hours, days, or years. This was observed with TRPH, 



