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Acidity Scale of N-Heterocyclic Carbene Precursors: Can We Predict the Stability of NHC–CO₂ Adducts?

Author:
Wang, Zhen, Wang, Fang, Xue, Xiao-Song, Ji, Pengju
Source:
Organic letters 2018 v.20 no.19 pp. 6041-6045
ISSN:
1523-7052
Subject:
acidity, carbenes, carbon dioxide, chemical reactions, chemical structure, dimethyl sulfoxide, energy, heterocyclic nitrogen compounds, models
Abstract:
The acidity scale (∼14 pK units) of more than 90 triazolium, imidazolium, and imidazolinium based NHC precursors in DMSO was established systematically by a well-developed computational model. The substituent effects on the acidities of these NHC precursors were analyzed through acidity comparison and Hammett correlation. The binding energy (ΔG₁) of the reaction between NHC and CO₂ was also calculated and linearly correlates with the basicity of the corresponding NHC, which implies that the stability of the NHC–CO₂ adduct is essentially dictated by the basicity of NHC.
Agid:
6151966