|Various computational methods have been applied in order to explore potential energy surfaces (PES) and reaction mechanisms. Theoretical background and computational methods are introduced in chapter 1. Chapters 2-5 report four different studies exploring potential energy surfaces of inorganic and organic molecules in order to understand reaction mechanisms.
Chapter 2 reports an investigation of the singlet and triplet potential energy surfaces of BCP isomers. From constructed PES, intramolecular rearrangment mechanisms are studied, possible dissociation pathways are discussed, a conical intersection is located, and Renner-Teller species are investigated.
Chapter 3 reports the dissociation mechanism of phosphorus-containing hyponitrites at the B3LYP level. The cis-hyponitrite, XON=NOX (X=PF2, OPF2), is predicted to concertedly decompose to N2 plus phosphorus-containing radicals or to N2O plus the µ-oxo phosphorus species. The trans-hyponitrite can only decompose to N2 plus the phosphorus-containing radicals because there is a very high barrier for rearrangement to cis-hyponitrite. However, the silver cation is predicted to reverse the order of the two transition states through stronger interactions with the oxygen atoms in the transition state of the N2O-producing pathway.
Chapter 4 explains the reactions mechanism of “stable” bis(amino)silylene with halomethanes and reports that the reactions occur via a radical mechanism. To explain the discrepancy of the theoretical model chemistry with experimental observations, substituent effects on the nitrogen atoms and halogen effects on the halomethanes are investigated which explain experimental observations.
In Chapter 5, the reaction of atomic carbon with formaldehyde is reported. The possible singlet excited carbene (1B1) formation pathways are investigated by analyzing the singlet and triplet potential energy surfaces of ketene. The production of 1B1 methylene from deoxygenation by 1D carbon and potential energy surface crossing along the C-C and C-O bond stretching are considered.