Quantum Chemical Prediction of Equilibrium Acidities of Ureas, Deltamides, Squaramides and Croconamides

Abstract

Robust quantum chemical methods are employed to predict the pKas of several families of dual hydrogen-bonding organocatalyts/anion receptors, including deltamides and croconamides as well as their thio-derivatives. The average accuracy of these predictions is about 1 pH unit, and allow for a comparison of the acidity between classes of receptors and for quantitative studies of substituent effects. These computational insights further explain the relationship between pKa and chloride anion affinity of these receptors that will be important for designing future anion receptors and organocatalysts.