Issue 3, 2009

Basicity of organic bases and superbases in acetonitrile by the polarized continuum model and DFT calculations

Abstract

The basicities of a large number of organic bases and superbases, including nitrogen basic centers in various chemical environments occurring in phosphazenes, amidines, amines, anilines and pyridines, have been studied in acetonitrile by the isodensity polarized continuum model employing two DFT computational schemes differing in the basis sets for final single-point calculations. It turned out that the B3LYP/6-311+G(d,p)//B3LYP/6-31G(d) method serves the purpose giving good agreement for basicities with experiment for both gas phase and acetonitrile solutions treating widely different bonding situations of basic nitrogen atoms on an equal footing. An attempt is made to correlate the experimental pKa(MeCN) values with the proton affinities (PA) in MeCN. The results are less accurate than those achieved by using basicities in acetonitrile. In particular, the PA(MeCN)s frequently failed in reproducing the pKa(MeCN) values in systems possessing multiple intramolecular hydrogen (IMH) bonds formed via corona effects. In such cases the use of basicities is mandatory instead. A useful corollary of these calculations on systems with multiple IMH bonds is that comparison of the theoretical and experimental pKa values can provide an insight into the structure of the most stable conformations in solutions.

Graphical abstract: Basicity of organic bases and superbases in acetonitrile by the polarized continuum model and DFT calculations

Supplementary files

Article information

Article type
Paper
Submitted
26 Aug 2008
Accepted
17 Oct 2008
First published
11 Dec 2008

New J. Chem., 2009,33, 588-597

Basicity of organic bases and superbases in acetonitrile by the polarized continuum model and DFT calculations

Z. Glasovac, M. Eckert-Maksić and Z. B. Maksić, New J. Chem., 2009, 33, 588 DOI: 10.1039/B814812K

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