Molecular Recognition in Mechanochemistry: Insights from Solid‐State NMR Spectroscopy

Angewandte Chemie, vol. 136

Abstract

Abstract Molecular‐recognition events are highly relevant in biology and chemistry. In the present study, we investigated such processes in the solid state under mechanochemical conditions using the formation of racemic phases upon reacting enantiopure entities as example. As test systems, α‐(trifluoromethyl)lactic acid (TFLA) and the amino acids serine and alanine were used. The effects of ball‐milling and resonant acoustic mixing (RAM) on the formation of racemic phases were probed by using solid‐state Nuclear Magnetic Resonance (NMR) spectroscopy. In a mixer mill, a highly efficient and fast racemic phase formation occurred for both TFLA and the two amino acids. RAM led to the racemic phase for TFLA also, and this process was facilitated upon employing pre‐milled enantiopure entities. In contrast, under comparable conditions RAM did not result in the formation of racemic phases for serine and alanine.

Authors 11

1. Calogero Quaranta Aachen Institute of Organic Chemistry

   RWTH Aachen University

   Affiliation as printed

   Institute of Organic Chemistry RWTH Aachen University Landoltweg 1 52074 Aachen Germany

2. Igor d’Anciães Almeida Silva

   Max Planck Institute for Chemical Energy Conversion

   Affiliation as printed

   Max Planck Institute for Chemical Energy Conversion Stiftstr. 34–36 45470 Mülheim/Ruhr Germany

3. Sven Moos Aachen Institute of Technical and Macromolecular Chemistry

   Max Planck Institute for Chemical Energy Conversion · RWTH Aachen University

   Affiliation as printed

   Institute of Technical and Macromolecular Chemistry RWTH Aachen University Worringerweg 2 52074 Aachen Germany

   Max Planck Institute for Chemical Energy Conversion Stiftstr. 34–36 45470 Mülheim/Ruhr Germany

4. Ettore Bartalucci Aachen Institute of Technical and Macromolecular Chemistry

   Max Planck Institute for Chemical Energy Conversion · RWTH Aachen University

   Affiliation as printed

   Institute of Technical and Macromolecular Chemistry RWTH Aachen University Worringerweg 2 52074 Aachen Germany

   Max Planck Institute for Chemical Energy Conversion Stiftstr. 34–36 45470 Mülheim/Ruhr Germany

5. Leeroy Hendrickx Aachen Institute of Technical and Macromolecular Chemistry

   RWTH Aachen University

   Affiliation as printed

   Institute of Technical and Macromolecular Chemistry RWTH Aachen University Worringerweg 2 52074 Aachen Germany

6. Benjamin M. D. Fahl Aachen Institute of Crystallography

   RWTH Aachen University

   Affiliation as printed

   Institute of Crystallography RWTH Aachen University Jägerstr. 17–19 52066 Aachen Germany

7. Claudia Pasqualini Aachen Institute of Organic Chemistry

   University of Siena · RWTH Aachen University

   Affiliation as printed

   Department of Biotechnology Chemistry and Pharmacy University of Siena via Aldo Moro, 2 I-53100 Siena Italy

   Institute of Organic Chemistry RWTH Aachen University Landoltweg 1 52074 Aachen Germany

8. Francesco Puccetti Aachen Institute of Organic Chemistry

   RWTH Aachen University

   Affiliation as printed

   Institute of Organic Chemistry RWTH Aachen University Landoltweg 1 52074 Aachen Germany

9. Mirijam Zobel Aachen Institute of Crystallography

   RWTH Aachen University

   Affiliation as printed

   Institute of Crystallography RWTH Aachen University Jägerstr. 17–19 52066 Aachen Germany

10. Carsten Bolm Aachen Institute of Organic Chemistry

    RWTH Aachen University

    Affiliation as printed

    Institute of Organic Chemistry RWTH Aachen University Landoltweg 1 52074 Aachen Germany

11. Thomas Wiegand Aachen Institute of Technical and Macromolecular Chemistry

    Max Planck Institute for Chemical Energy Conversion · RWTH Aachen University

    Affiliation as printed

    Institute of Technical and Macromolecular Chemistry RWTH Aachen University Worringerweg 2 52074 Aachen Germany

    Max Planck Institute for Chemical Energy Conversion Stiftstr. 34–36 45470 Mülheim/Ruhr Germany