From the Felkin‐Anh Rule to the Grignard Reaction: an Almost Circular 50 Year Adventure in the World of Molecular Structures and Reaction Mechanisms with Computational Chemistry**

This rosarium article relates the adventure started 50 years ago of a computational chemist who was interested in molecules; what are they, what are their shape and how do they react. The story describes results, still valid today, obtained with highly simplified models of chemical reality and elementary computational methods and the gain resulting from the use of better models and more elaborate computational methods. It was necessary to select examples. In this presentation, focus is on hydride and dihydrogen complexes as well as on nucleophiles. Nucleophiles were considered as free hydrides in gas phase at the start of the rosarium while the Grignard reaction is treated with ab initio molecular mechanisms at the end of it.