Formation of humic substances in the reaction of D-glucose with p-toluidine in anhydrous ethanol
https://doi.org/10.21285/2227-2925-2020-10-2-188-195
Abstract
The aim of the study was to investigate the processes of formation and structural group composition of the products formed during the reaction of D-glucose with p-toluidine in anhydrous ethanol using electronic and vibrational spectroscopy methods. The evolution of the profiles of the electronic spectra of working solutions shows the formation of a chromophore system: clear peaks at 380 and 440 nm are already present at a reaction time of 60 min. The appearance of an additional maximum at 520 nm (90, 120 min) likely corresponds to the formation of chromophores in condensed structures, as confirmed by a decrease in the values of the E4/Е6 indices over time. The dynamics of the transformation of structural elements is also clearly seen in the analysis of IR spectra: as the reactions proceed, the CH aliphatic component of the structure decreases, while the aromatisation and functionalisation of products by chromophore groups increases. For products obtained between 90 and 120 min, a clear band at 1656 cm-1, attributed to stretching vibrations of multiple bonds in conjugated C=C–C=O systems and azomethine fragments, indicates the of condensation reactions. In the spectra of insoluble solid products fractionated by water, the intensity of the bands at 1656 and 1190 cm-1 is significantly reduced; this is possibly due to the transfer of some of the coloured low molecular weight products to the aqueous phase. A comparison of the IR Fourier transform spectra of the final solid products with the spectra of natural and synthetic humic-like substances indicates their similar structural group composition. The intensity of the bands at 1620, 1508 and 815 cm-1 indicates a significant contribution of the aromatic component to the structure of the products of water-insoluble fractions; the water-soluble fractions mainly include aliphatic oxygen-containing structures resulting from the oxidative destruction of the initial carbohydrate. The synthesised products seem promising as convenient plant growth regulators with controlled release of the active substance.
About the Authors
I. S. Cherepanov
Udmurt State University
Russian Federation
Russian Federation
Cand. Sci. (Chemistry), Associate Professor
1 Universitetskaya St., Izhevsk 426034, Russian Federation
P. S. Kryukova
Udmurt State University
Russian Federation
Russian Federation
Student
1 Universitetskaya St., Izhevsk 426034, Russian Federation
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Review
For citations:
Cherepanov I.S., Kryukova P.S. Formation of humic substances in the reaction of D-glucose with p-toluidine in anhydrous ethanol. Proceedings of Universities. Applied Chemistry and Biotechnology. 2020;10(2):188-195. https://doi.org/10.21285/2227-2925-2020-10-2-188-195
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