Eliminierungsreaktionen an Kationen in Gasphase II Essigsäureeliminierung aus Androstanylacetaten

Elimination of acetic acid from the molecular ions of the epimeric androstanylacetates is investigated applying specific ²H-labelling and analysis of metastable transitions. Only 17β-androstanylacetate eliminates acetic acid in a 1,2-fashion to an extent of 16%. This contribution is shown to be a specific cis-elimination and after comparison with water-elimination in the corresponding alcohol a McLafferty type mechanism is attributed, which then appears to require a planar transition state.     

Carbonylverbindungen als Kohlenstoffsäuren

Proton transfer to carbon bases (enols) and from carbon acids (ketones) determines the rate of ketonization and enolization reactions, respectively. Kinetic studies performed over the last two decades have provided absolute rate constants and reliable equilibrium constants for a broad range of prototropic reactions. Structure-reactivity and free energy relationships now form a reliable framework to predict the reactivity of the transient species involved in these fundamental reactions. Comparison of reaction rates in aqueous solution with rates achieved by enzymes reveals the striking efficiency of the latter.