Chemical formation, destruction and rearrangement processes compete with each other in natural processes. The understanding of the specific atomic-level factors steering chemical competition towards a macroscopic outcome is one of the main aims of physical chemistry.
This dissertation focuses on the dynamics and kinematics of competing processes in several of gas-phase ion-molecule reactions relevant in two distinct realms, namely the interstellar medium (ISM) and the organic chemistry laboratory. A combination of Crossed Beams and Velocity Map Imaging (VMI) spectrometry has been used in order to monitor the angle- and energy differential cross section of each product species.
The first series of investigations report on astrochemically relevant reactions in which different product species can be formed. The reactions H3+ + CO and HOCO+ + CO have been investigated in order to unravel the dynamics and relative abundance of the competing HCO+ and HOC+ product isomer formations. Moreover, competing charge and proton transfer reactions have been identified and analyzed for the ion-radical reaction H3+ + CH3.
The second part of the thesis deals with an important reaction in organic chemistry, namely the bimolecular nucleophilic substitution (SN2). The first study investigates possible preferential formations of NCCH3 or CNCH3 in CN- + CH3I combining electronic structure calculations and reactive scattering experiments. In a second study, secondary pathways competing with SN2 in F- + CH3I have been identified and their dynamical features have been discussed. Finally, this simplest X- + CH3Y case has been extended to more complex reactions and the competition between SN2 and base induced elimination (E2) has been investigated as a function of steric and energetic factors. First indications of inherent dynamical features in E2 reactions are reported.