Abstract:
This contribution delivers an overview over the wide scientific work of Jakob Meisenheimer. His first notable achievement was the correct interpretation of the adduct formed between nitro-group containing arenes and bases (Meisenheimer complexes). A further milestone was the revision of the syn-anti assignment of stereoisomeric oximes and the consequential realization, that in the course of the Beckmann rearrangement a migration of the residue in the anti-position occurs. With elegant experiments, Meisenheimer supported the ammonium theory of Hantzsch and Werner about the tetravalency of nitrogen in ammonium compounds. Meisenheimer succeeded with the first racemate separation of chiral amine oxides and phosphine oxides and he recognized early, that amines must have a pyramidal structure, although a separation of unsymmetrically substituted tert. amines in optical antipodes never succeeded. He explained this discrepancy by a fast inversion between the two antipodes, with a planar arrangement as the middle position. Meisenheimer disproved many examples in the literature, in which isomerism was explained by an „asymmetrical nitrogen atom“. As a „by-product“ of his work to separate the racemates of tert. amine oxides, Meisenheimer discovered the rearrangement of allyl/benzyl substituted amino oxides in O-allyl/benzylhydroxylamines (Meiseheimer rearrangement). In the, at that time, young area of biochemistry Meisenheimer investigated the chemism of the alcoholic, lactic acid and butyric fermentation and together with Buchner worked on cell-free fermentation processes. In a series on the structure and reactivity of Grignard reagents, Meisenheimer succeeded amongst other things in explaining the Grignard reduction, which depending on structure and conditions can compete with the actual Grignard addition. In mechanistic studies on substitution and addition, Meisenheimer delivered the first explanation for the Walden inversion, the trans-addition of bromine to double bonds and the “abnormal” substitution of allyl compounds.