The aim of this thesis was to probe the possibility to quantify the acidity of various classes of Lewis acids by NMR spectroscopic methods. Carbocations, silyliumions, thioureas, as well as Lewis acid assisted Lewis acids were among the investigated classes. Furthermore, a relationship between the experimentally quantified acidities and the catalytic activities of the Lewis acids in simple Diels-Alder reactions was investigated. Thereby, acidity-activity relationships were found and class specific questions could be answered.
