Klaus Schöffel

Titanium-silicalite catalyzed epoxidation of ethylene with hydrogen peroxide. A theoretical study

Abstract Active sites in titanium silicalite (TS-1) for selective oxidation of ethylene with H 2 O 2 were studied by using ab initio quantum chemical methods. Models of the active sites were energy optimised and the interaction with H 2 O and H 2 O 2 calculated. The binding situation of the resulting titanium hydroperoxo compounds were explained and transition states and activation energy for the epoxidation of ethylene were computed. The transition states were characterised by calculating the vibrational frequencies.

Vibrational frequencies of AlF3: An ab initio MO study evaluating different methods on a tricky case

Abstract The vibrational frequencies of AlF 3 have been calculated with ab initio methods at the Hartree-Fock level, at correlated levels (MP2, QCISD, MCSCF) and with the LDF method including local (LSD) and non-local spin density (NLSD) functions. The basis set sensitivity was examined with a large number of basis sets including polarization and diffuse functions. The calculations do not confirm the assignment of v 4 to 263 cm −1 , but suggest a frequency of ≈ 240 cm −1 for this mode. The v 1 mode most probably is close to 670–675 cm −1 . The lowest recommendable level for vibrational analysis of AlF 3 , and probably also for related species, seems to be HF/6-31 + G ∗ .

Substituent crowding in nitrobenzenes

Abstract The rotational motion of adjacent nitro groups in 1,2-dinitrobenzene and 1,2,4-trinitrobenzene has been investigated using X-ray diffraction and quantum chemical calculations. Pilot calculations on nitrobenzene indicate that density functional theory provides reliable geometries for this type of compound. Using this method for the substituted compounds, we find that rotation of the two adjacent nitro groups can take place quite freely within a groove in the potential surface that defines an interlocking cogwheel mode. The experimental structures of both molecules are found to have nitro group configurations corresponding to this mode of motion.

The Role of Computational Molecular and Material Science for the Chemical Industry

“Every attempt to employ mathematical methods in the study of chemical questions must be considered profoundly irrational and contrary to the spirit of chemistry. If mathematical analysis should ever hold a prominent place in chemistry — an aberration which is happily almost impossible — it would occasion a rapid and widespread degeneration of that science.”