A Supramolecular Model for the Co-Catalytic Role of Nitro Compounds in Brønsted Acid Catalyzed Reactions.
Chemistry
; 26(48): 10976-10980, 2020 Aug 26.
Article
em En
| MEDLINE
| ID: mdl-32365243
ABSTRACT
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. In this work, an atomistic model for the catalytically active form for an alcohol dehydroazidation reaction is presented, which is generated by DFT calculations and 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 predictors for experimental reaction rates. By applying the model to a chemically diverse set of potential promoters, it was 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.
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Base de dados:
MEDLINE
Tipo de estudo:
Prognostic_studies
Idioma:
En
Ano de publicação:
2020
Tipo de documento:
Article