Preprint Article Version 1 This version is not peer-reviewed

Quantification of σ–Holes and Their Use as a Descriptor for the Theoretical Calculation of pKa Values for Carboxylic Acids

Version 1 : Received: 16 October 2018 / Approved: 19 October 2018 / Online: 19 October 2018 (05:29:19 CEST)

How to cite: Caballero-García, G.; Mondragón-Solórzano, G.; Torres-Cadena, R.; Díaz-García, M.; Sandoval-Lira, J.; Barroso-Flores, J. Quantification of σ–Holes and Their Use as a Descriptor for the Theoretical Calculation of pKa Values for Carboxylic Acids. Preprints 2018, 2018100434 (doi: 10.20944/preprints201810.0434.v1). Caballero-García, G.; Mondragón-Solórzano, G.; Torres-Cadena, R.; Díaz-García, M.; Sandoval-Lira, J.; Barroso-Flores, J. Quantification of σ–Holes and Their Use as a Descriptor for the Theoretical Calculation of pKa Values for Carboxylic Acids. Preprints 2018, 2018100434 (doi: 10.20944/preprints201810.0434.v1).

Abstract

Theoretical approaches to calculate pKa values for Brønsted acids is a challenging task that, most of the time, involves sophisticated and time-consuming methods. Therefore, heuristic approaches are efficient and appealing methodologies to approximate these values. Herein, by considering the electrostatic potential on acidic hydrogen atoms in a similar fashion that a σ–hole is defined, we calculated the maximum surface potential, VS,max, and used it as a descriptor to correlate it with experimental acidity constants. These values were calculated using the CPCM implicit solvent model (water) with six different methods: five density functionals and the Møller–Plesset second order perturbation theory. Six different basis sets were combined with each method in order to benchmark a total of thirty-six levels of theory. Overall, 1080 calculations were performed and found to correlate with experimental data. The ωB97X-D/6-31+G(d,p) level of theory stands as the best one for consistently reproduce the reported pKa values.

Subject Areas

pKa; hydrogen bond; σ–hole

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