Modern chemistry experiences a fast development of new reactions with dominance in organometallics and recently also organocatalysis. The massive synthetic progress however greatly foreruns mechanistic studies and the deeper insight is often rather limited. This large unexplored area accordingly challenges pioneering research and formulation of new concepts in chemistry. The present research project uses the most powerful tools of several research disciplines and aims towards the investigation of the elementary steps in organic reactions by means of mass spectrometry (MS) in combination with electrospray ionization (ESI) and quantum chemistry with a particular focus on ion spectroscopy.The research will concentrate on elementary reactions in catalysis, e.g. the interaction of catalysts with substrates or bimolecular reactions of reactant/catalyst complexes. A major innovative contribution consists in applying ion spectroscopy for the structural characterization of reaction intermediates using a newly proposed tandem mass spectrometer with a cooled linear ion trap, which will allow two-photon experiments with IR and UV tunable lasers. The experiments will provide specific information about various intermediates and will help to disentangle even complicated mixtures or isomeric ions. In addition, an innovative experiment is designed, in which bimolecular reactivity of isobaric ions will be studied individually. Kinetics of selected reactions in solution will also be followed by ESI/MS. The combined efforts of these different approaches will provide a comprehensive understanding of the reaction mechanisms and will lead to the formulation of new general concepts in organic and organometallic reactivity.