On Friday, Aug 29, 2014 the defence of PhD thesis Acidity and basicity in non-aqueous media: importance of solvent properties and purity prepared by Karl Kaupmees took place.

Karl’s thesis is focused on solvent characteristics, that influence the pKa measurements
in non-aqueous media and is divided into two major sections. In the first part, pKa
measurements for two sets of compounds – pKa of chiral strongly acidic catalysts (e.g. the BINOL, NTPA and JINGLE families) and pKa of fluoro- and chloro-substituted phosphanes are carried out revealing the importance of knowledge of solvent properties in order to achieve accurate and reliable results. In collaboration with our partner research groups it was also discovered that the acidities of the involved compounds have strong impact on the respective catalytic processes.

In the second part of the thesis, the influence of water, at low concentration, below 1% (w/w), is systematically studied on the relative acidities and basicities. It is quantitatively shown, that acids are much more influenced by the increase of water content in solvent, compared to bases. Higher impacts are observed in case of acids and bases with localized charges in corresponding ions.

In order to quantify the charge delocalization in ions, for the first time, two computational parameters WAPS (charge delocalization parameter for anions) and WANS (charge delocalization parameter for cations) are proposed. The strength of the acids as well as the nature of acidity center are shown to affect the changes in relative acidity upon increase of water content. Recently it has also been discovered that there is a good correlation between the WAPS charge delocalization parameter and the electrospray (ESI) ionization efficiency of the compounds.

The defence was very successful and it is expected that the results will be of interest to a wide community of chemists and technologists.



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