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A Supramolecular Model for the Co‐Catalytic Role of Nitro Compounds in Brønsted Acid Catalyzed Reactions
Author(s) -
MontalvoAcosta Joel J.,
Dryzhakov Marian,
Richmond Edward,
Cecchini Marco,
Moran Joseph
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202000368
Subject(s) - catalysis , supramolecular chemistry , chemistry , brønsted–lowry acid–base theory , molecule , nitro , alcohol , solvent , acid catalysis , reaction mechanism , computational chemistry , combinatorial chemistry , organic chemistry , alkyl
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 p K a of the acid and the bulk properties of a solvent, but also the weak interactions between all molecules in solution.