Naslov
Protonation and homoconjugation equilibria in aprotic organic solvents

Autori
Bregović, Nikola ; Barišić, Dajana ; Tomišić, Vladislav

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
13th International Congress of Young Chemists : Book of Abstracts / - Varšava : Chemical Scientific Society, 2015, 53-53

ISBN
978-83-61037-28-6

Skup
International Congress of Young Chemists

Mjesto i datum
Kraków, Poljska, 07.10.2015. - 11.10.2015

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Nije recenziran

Ključne riječi
protonation ; homoconjugation ; aprotic solvents ; UV-Vis ; NMR ; calorimetry

Sažetak
The acid-base equilibria in aprotic organic solvents, like acetonitrile (MeCN) and dimethyl sulfoxide (DMSO) often include several equilibria, i.e. protonation, homoconjugation, and dimerization of the anion. Although extensive studies of acid-base behaviour in MeCN and DMSO were reported in literature, problems in the quantitative thermodynamic characterisation of the corresponding equilibria remained unresolved, especially in the case of acids prone to dimerization and homoconjugation. Therefore, reliable data, essential for accurate interpretation of results regarding more complex supramolecular systems containing such anions and their protonated forms, can be rarely found. In this work the protonation and homoconjugation of several anions ubiquitous in chemical science, AcO–, H2PO4–, and F–, were investigated in MeCN and DMSO by several physico-chemical methods, including UV-Vis, ITC, conductometric, and 31P NMR titrations. Spectrophotometric titrations of bromthymol with the TBA salts of the investigated anions enabled reliable determination of equilibrium constants for both protonation and homoconjugation. Conductometric and microcalorimetric titrations of the salt solutions with the corresponding acid were used to study the homoconjugation constant independently of protonation. The determined constants were in good agreement with those obtained by spectrophotometry. Furthermore, microcalorimetric titrations enabled the determination of the thermodynamic functions of homoconjugation reactions, i.e. ΔrH and ΔrS, which was, to our knowledge, first attempt to measure these values. The results obtained for the acetonitrile solutions of TBAH2PO4 and H3PO4 indicated that a more complex equilibrium system was established. The species formed in these solutions were identified by the use of 31P NMR spectroscopy and their stability was again determined by several methods. The experimental approach used in the research will be presented in detail, along with the possibilities, as well as the limitations of each method used. The gathered data will be discussed from the thermodynamic and structural point of view and compared with literature data. Acknowledgements: The work was funded by Croatian science foundation (SupraCAR: IP-2014-09-7309)

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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