April 01, 2025

Challenging HSAB: Reactive Molecules and Nucleophiles

44 minutes

Contributors:

Justus Reitz

Dr. Kevin Hares

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Key takeaways:

Limitations of the HSAB Concept: While the HSAB (Hard and Soft Acids and Bases) concept is a familiar tool in chemistry for predicting reaction outcomes, it falls short as a reliable predictive model.

The Mayr Nucleophilicity Scale: The Mayr scale, a logarithmic measure, provides distinct numerical values to gauge nucleophile strength.

Stabilization of Reactive Intermediates: By employing super strong nucleophiles (like mesoionic olefins), the team was able to synthesize stable diazoalkenes, opening up new possibilities for investigating reaction mechanisms and functional group behavior.

Advancing Fundamental Research in Organic Chemistry: Beyond immediate applications, the episode emphasizes the value of basic research. Exploring the limits of nucleophilicity and reactivity not only refines existing theoretical models but also lays the groundwork for future innovations in

In this episode of Innovate and React, I am talking with Justus Reitz, a chemist from TU Dortmund University, about the limitations of the HSAB (Hard and Soft Acids and Bases) concept in predicting reaction outcomes. We explore an alternative approach using the nucleophilicity scale developed by the Mayr group, which offers a more accurate prediction method. Justus shares insights from his PhD research on stabilizing highly reactive molecules, particularly the synthesis and stabilization of diazoalkenes. We discuss how the Mayr nucleophilicity scale can facilitate understanding and controlling chemical reactions, bridging the gap between theoretical concepts and practical applications.

Further reading:

Mayr, Herbert, et al. ‘Farewell to the HSAB Treatment of Ambident Reactivity’. Angewandte Chemie International Edition, vol. 50, no. 29, July 2011, pp. 6470–505. https://doi.org/10.1002/anie.201007100

Mayr, Herbert, and Matthias Patz. ‘Scales of Nucleophilicity and Electrophilicity: A System for Ordering Polar Organic and Organometallic Reactions’. Angewandte Chemie International Edition in English, vol. 33, no. 9, May 1994, pp. 938–57. https://doi.org/10.1002/anie.199409381

Hansmann, Max M., et al. ‘Stable Mesoionic N‐Heterocyclic Olefins (mNHOs)’. Angewandte Chemie, vol. 132, no. 14, Mar. 2020, pp. 5831–36. https://doi.org/10.1002/ange.201914571

Antoni, P. W., et al. ‘Isolation and Reactivity of an Elusive Diazoalkene’. Nature Chemistry, vol. 13, no. 6, June 2021, pp. 587–93. https://doi.org/10.1038/s41557-021-00675-5

Eitzinger, Andreas, et al. ‘Pushing the Upper Limit of Nucleophilicity Scales by Mesoionic N ‐Heterocyclic Olefins’. Angewandte Chemie International Edition, vol. 62, no. 40, Oct. 2023, p. e202309790. https://doi.org/10.1002/anie.202309790

If you have an interesting topic to talk about in a future episode sen me an email to [email protected] or find me on LinkedIn. Also check out the podcast website https://innovateandreact.com

Many thanks to aloc for provinding the music.

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