An Acidity Scale of
Triazolium-Based NHC Precursors in DMSO
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Abstract
An acidity scale of triazolium-based
N-heterocyclic carbene precursors was established by measuring 25
compounds’ (<b>10a</b>–<b>15b</b>) equilibrium
acidities in dimethyl sulfoxide (DMSO) solution using overlapping
indicator method. The p<i>K</i><sub>a</sub> values ranged
from 12.08 to 15.5, responding not only to the <i>N</i>-aryl
motif, but also to the core structure. Excellent correlation was observed
between the p<i>K</i><sub>a</sub> values and the Hammett
substituent constants (σ<sub>p</sub>)
