| Experimental kinetic isotope effects and experimental transition states for several reactions along with some newly developed techniques for mechanism elucidation are discussed.;The reactions studied include electrophillic additions (bromination, epoxidation, dichlorcarbene) to pentene, Diels-Alder (retro, Lewis acid catalyzed, inverse electron demand) reactions, hydrogen atom abstraction (TBHP), and decarboxylation of 1,3-dimethylorotic acid.;Experimental transition states were suggested when there was good agreement between experiment and theory. The experimental transition state obtained for the epoxidation of pentene settled a 40 year old debate on the synchronicity of C-O bond formation. Dichlocarbene addition to pentene was the first experimental evidence for a non least-motion approach. The experimental transition state for the decarboxylation of 1,3-dimethylorotic acid may aid in explaining the difference between the uncatalyzed and enzymatic reactions.;New techniques for mechanism elucidation are discussed. They include the separation of primary and secondary isotope effects from starting material reactivities, the determination of 17O and 18O isotope effects, and stereochemical labeling. |
