Inside Back Cover: Dynamic Cross‐Exchange in Halophosphonium Species: Direct Observation of Stereochemical Inversion in the Course of an S N 2 Process (Angew. Chem. Int. Ed. 6/2018)

Unlike an unruly brolly or the striking lily of the Nile, the celebrated umbrella‐like S N 2 inversion has not been directly observed until now. In their Communication on page 1480 ff., K. Nikitin, D. G. Gilheany, et al. demonstrate direct observation of inversion in a low‐temperature NMR‐EXSY experiment using an inseparable mixture of isomers. Fast nucleophilic attack of a halide ion on a phosphonium center has all the characteristics of an associative process and leads to inversion of the P configuration.