Nontronite Catalysis in Polycondensation of Pyrogallol and Glycine and the Associated Reactions

Abstract

AbstractThe objective of this study was to investigate the catalytic power of nontronite (0.2‐2 µm) in the polycondensation of pyrogallol (1,2,3‐trihydroxybenzene) and glycine and the associated reactions involving the ring cleavage of pyrogallol and the decarboxylation and deamination of glycine in systems free of microbial activities. At the end of a 90‐h reaction period, nontronite catalyzed the ring cleavage of pyrogallol, as shown by the release of CO2. The release of CO2 in the nontronite‐pyrogallol system was six times higher than that for pyrogallol alone. Nontronite also catalyzed decarboxylation and deamination of glycine, as shown by the release of CO2 and NH3. The ability of nontronite to catalyze deamination of glycine was substantially enhanced by the presence of pyrogallol. Polycondensation of glycine and pyrogallol was greatly catalyzed by nontronite. This is indicated by the absorbances of the molecular visible absorption spectroscopy of the supernatants, yields of total N‐containing humic acids (HA) and fulvic acids (FA) and the fraction of glycine converted to nitrogenous polymer. The infrared (IR) and electron spin resonance (ESR) spectra of HA and FA formed in the supernatants of the reaction systems were similar to those of soil HA and FA. The sequence for the amounts of the total humic polymers formed in the system was: nontronite‐glycine‐pyrogallol > nontronite‐pyrogallol > glycine‐pyrogallol > pyrogallol. The catalytic effects of nontronite on the C turnover, N transformations, and humic substance formation in soils thus merit attention.