Małgorzata Czaja

Potentiometric investigation of acid dissociation and anionic homoconjugation equilibria of substituted phenols in dimethyl sulfoxide

Abstract Standard acidity constants, K a DMSO (HA), expressed as p K a DMSO (HA) values, and anionic homoconjugation constants, K DMSO AHA − , (in the form of lg K DMSO AHA − values) have been determined for 11 substituted phenol–phenolate systems a polar protophilic aprotic solvent, dimethyl sulfoxide (DMSO) with a potentiometric titration. A linear relationship has been determined between lg K DMSO AHA − and p K a DMSO (HA). The tendency towards anionic homoconjugation in these systems increases with increasing p K a DMSO (HA) that is with declining phenol acidity. The p K a DMSO (HA) are correlated with both p K a W (HA) water and other polar non-aqeous solvents.

A study of energetics of formation of heterocomplexed cations of trimethylamine N-oxide by using ab initio methods

Abstract Ab initio methods at the Restricted Hartree Fock (RHF) and Moller–Plesset (MP2) levels were used to investigate the energetics of heterocomplexed cation formation by trimethylamine N-oxide as the proton donor and substituted pyridine N-oxides of different basicities. For calculation of the energies and Gibbs free energies of cationic heteroconjugation, a 6–31G∗ basis set was used in which, the polarization function was accounted for. The calculated energies, ΔEBHB1+, and Gibbs free energies, ΔGBHB1+, of formation of the heterocomplexes in vacuo have been found to correlate well with the corresponding calculated energies and Gibbs free energies of protonation of the proton acceptor (at fixed proton donor basicity) and slightly less so with experimental cationic heteroconjugation constants, log K BHB 1 + , determined in nitromethane.