INTERACTION OF AQUACOBALAMIN WITH DIHYDROXYBENZENES

The interaction of aquacobalamin (H2OCbl) with dihydroxybenzenes – hydroxyquinone, catechol, resorcinol in aqueous solutions has been studied using UV-vis spectrometry. The rate constants of redox reactions have been determined. Their reaction mechanisms have been suggested. It is shown that reaction of aquacobalamin with hydroquinone is accompanied by reduction of Cbl(III) to Cbl(II). The structure of corrin ligand does not change. Reduction of aquacobalamin is accompanied by substitution of water by hydroquinone with formation of unstable complex Cbl(III)-hydroquinone decomposing to Cbl(II) and phenoxy radical – the latter further disproportionates to p-benzoquinone and hydroquinone. The rate of reaction between aquacobalamin and hydroquinone in weakly acidic, neutral and weakly alkaline solutions is decreasing with the increase in pH due to formation of inert hydroxocobalamin. Reaction of aquacobalamin with catechol also gives Cbl(II), but this reaction proceeds much slower than reduction of aquacobalamin with hydroquinone under the same conditions. Reaction of aquacobalamin with resorcinol in acidic, neutral and alkaline solutions does not lead to any changes in UV-vis spectra. Therefore it is assumed that resorcinol does not react with H2OCbl. Based on the previous data and data obtained in this work the following sequence of reducing activity of dihydroxybenzenes in aqueous solutions was proposed: hydroquinone >> catechol > resorcinol. The stability of dihydroxybenzenes in aqueous solutions in the presence of aquacobalamin and in the absence of oxygen increases in the reverse order. The reason of high reducing ability of hydroquinone is assumed to be low dipole moment of hydroquinone molecule. For citation: Makarov S.V., Kiseleva A.G., Makarova A.S., Logacheva O.I. Interaction of aquacobalamin with dihydroxybenzenes. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2025. V. 68. N 3. P. 36-41. DOI: 10.6060/ivkkt.20256803.7163.