Original scientific paper

https://doi.org/10.5562/cca2472

Basicities of Strong Bases in Water: A Computational Study

Karl Kaupmees ; University of Tartu, Institute of Chemistry, 14a Ravila str, 50411 Tartu, Estonia
Aleksander Trummal ; National Institute of Chemical Physics and Biophysics, 10 Rävala Blvd., Tallinn 10143, Estonia
Ivo Leito ; University of Tartu, Institute of Chemistry, 14a Ravila str, 50411 Tartu, Estonia

Abstract

Aqueous pKa values of strong organic bases – DBU, TBD, MTBD, different phosphazene bases, etc – were computed with CPCM, SMD and COSMO-RS approaches. Explicit solvent molecules were not used. Direct computations and computations with reference pKa values were used. The latter were of two types: (1) reliable experimental aqueous pKa value of a reference base with structure similar to the investigated base or (2) reliable experimental pKa value in acetonitrile of the investigated base itself.
The correlations of experimental and computational values demonstrate that direct computations do not yield pKa predictions with useful accuracy: mean unsigned errors (MUE) of several pKa units were observed. Computations with reference bases lead to MUE below 1 pKa unit and are useful for predictions.
Recommended aqueous pKa values are proposed for all investigated bases taking into account all available information: experimental pKa values in acetonitrile and water (if available), computational pKa values, common chemical knowledge.

Keywords

superbases; quantum chemistry in solution; aqueous basicity; DBU

Hrčak ID:

131540

URI

https://hrcak.srce.hr/131540

Publication date:

22.12.2014.

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