Acidity and basicity in non-aqueous media: importance of solvent properties and purity
Date
2014-07-07
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Abstract
Käesolev töö koosneb kahest peamisest osast. Esimeses uuritakse kahe komplekti katalüütiliselt aktiivsete ainete happelis-aluselisi omadusi, mis toovad ilmekalt välja vajaduse teada täpselt kasutatava keskkonna omadusi. Fosfoonhapetel ja nende estritel põhinevate ainete juures leitakse sellest tulenevalt olulised vead kirjanduses avaldatud väärtustes, nende vigade tekkeallikaid uuritakse ja erinevused seletatakse. Triarüülfosfaanide pKa väärtuste mõõtmine toob välja atsetonitriili kui solvendi piirangud ja viib alternatiivse solvendi, 1,2-dikloroetaani, paralleelse kasutamiseni.
Väitekirja teises osas kvantiseeritakse süstemaatiliste mõõtmiste abil vee, kui kõige levinuma lisandi, mõju hape-alus tasakaaludele madalate kontsentratsioonide piirkonnas atsetonitriilis. Näidatakse, et happed on madalatest veesisaldustest rohkem mõjutatud kui alused. Samuti kvantiseeritakse veesisalduse mõju sõltuvus ainete happelis-aluseliste omaduste tugevusest, happelisuse/aluselisuse tsentrist ja laengu delokalisatsiooni määra ulatusest ioonses vormis.
The thesis consist of two major sections. Firstly, pKa values of two sets of catalytically active compounds are measured. These experiments emphasize the need to know the properties of the solvent. Serious errors are revealed in case of compounds derived from phosphonic acids and their esters. These disparities are further investigated and explained in detail. Measurements with triarylphosphanes bring the need for 1,2-dichloroethane as a second solvent next to acetonitrile, due to the limits of the latter. Secondly, the influence of water, the most common impurity in non-aqueous solvents, is systematically investigated at low concentrations in acetonitrile. It is shown that acids are more influenced by the rising water content compared to bases. The effect is studied by changing the strength of the acid-base properties of the compounds, the nature of the acidity/basicity center as well as the charge delocalization in ionized species.
The thesis consist of two major sections. Firstly, pKa values of two sets of catalytically active compounds are measured. These experiments emphasize the need to know the properties of the solvent. Serious errors are revealed in case of compounds derived from phosphonic acids and their esters. These disparities are further investigated and explained in detail. Measurements with triarylphosphanes bring the need for 1,2-dichloroethane as a second solvent next to acetonitrile, due to the limits of the latter. Secondly, the influence of water, the most common impurity in non-aqueous solvents, is systematically investigated at low concentrations in acetonitrile. It is shown that acids are more influenced by the rising water content compared to bases. The effect is studied by changing the strength of the acid-base properties of the compounds, the nature of the acidity/basicity center as well as the charge delocalization in ionized species.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone.
Keywords
mittevesikeskkonnad, lahustid, happelisus, aluselisus, non-aqueous media, solvents, acidity, alkalinity