A theoretical study on the mechanism and rate constants of luteolin and selenium dioxide.

CONTEXT

This study investigates the reaction mechanism of luteolin with selenium dioxide in ethanol. Through a detailed search for transition states and thermodynamic energy calculations, it was found that the reaction proceeds via two possible pathways, leading to the formation of products P1 and P2, respectively. A common feature of both pathways is that the first elementary step results in the formation of the intermediate INT1. Kinetic calculations indicate that, within the temperature range of 273 to 340 K, the apparent rate constant (k2) for the formation of intermediate INT1 is significantly larger than those of k3 and k4, and all three rate constants increase substantially with temperature. Interestingly, the product P1 from the first pathway is thermodynamically and kinetically feasible, and is in complete agreement with experimental results. In contrast, the product P2 from the second pathway contains a Se-O-Se ether bond, which exhibits dynamic stability in its molecular structure. In conclusion, this study not only validates the experimental findings but also provides theoretical guidance for the synthesis of novel organoselenium compounds.

METHODS

All calculations were performed using the DFT/M06-2X/6-31G(d,p) method. The solvent effect was considered by applying the IEFPCM model in all calculations. The free energy (∆G) of each compound at 298.15 K was obtained with a correction factor of 0.967. The apparent rate constants for each step were calculated over a temperature range from 273.15 to 373.15 K using transition state theory.