Chemistry Eur. J. [IFM]

Summary :

Nitro compounds are known to change reaction rates and kinetic concentration dependence of Brønsted‐acid‐catalyzed reactions. Yet, no mechanistic model exists to account for these observations. Herein we present an atomistic model for the catalytically active form for an alcohol dehydroazidation reaction, generated by DFT calculations. which consists of an H‐bonded aggregate of two molecules of Brønsted acid and two molecules of nitro compound. The computed O‐H stretching frequencies for the aggregate indicate they are stronger acids than the individual acid molecules and serve as excellent predictors for experimental reaction rates. Applying the model to a chemically diverse set of potential promoters, we predicted and verified experimentally that sulfate esters induce a similar co‐catalytic effect. The important implication is that Brønsted‐acid catalysis must be viewed from a supramolecular perspective that accounts for not only the pKa of the acid and the bulk properties of a solvent, but also the weak interactions between all molecules in solution.

Graphical Abstract :

 

Reference :

Joel J. Montalvo-Acosta, Marian Dryzhakov, Edward Richmond, Marco Cecchini, and Joseph Moran

A Supramolecular Model for the Co‐Catalytic Role of Nitro Compounds in Brønsted Acid Catalyzed Reactions

Chemistry. A European Journal, First published: 04 May 2020, DOI :https://doi.org/10.1002/chem.202000368

Contact chercheur :

Marco Cecchini, équipe IFM (https://ifm.chimie.unistra.fr/), Institut de Chimie (UMR 7177).