Theoretical study on vapour phase Beckmann rearrangement of cyclohexanone oxime over a high silica MFI zeolite

We have studied an activation mechanism of cyclohexanone oxime in a cavity of high silica MFI zeolite by using PIO analysis proposed by Fujimoto et al. DFT calculation reveals that the bond length of N–OH becomes longer when water coordinates on oxygen of oxime. The PIO clearly shows out-of-phase interaction between N and O. This out-of-phase interaction is also observed in the PIO of oxime/MFI zeolite cluster model and weakens the NO bond. Hydrogen bond of Si–OH of nest silanols to oxime is a trigger of vapour phase Beckmann rearrangement.