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Solvation and proton transfer phenomena in phenol derivative-tertiary amine-aprotic solvent systems

Ilczyszyn M.

Bulletin of the Polish Academy of Sciences. Chemistry

2000

Vol. 48, No. 1

91-100

Proton transfer (PT) equilibria inside hydrogen-bonded complexes of phe-nols (AH) with triethylamine and JV-methylpiperidine (B), A-H...B A - o -H-B+, dissolved in cooled (up to 113 K) aprotic solvents are analysed using H NMR results. Two categories of situations, depending on the acid and base initial concentrations, are considered: slower and faster PT for the Cg : CAg w 2 and Cg : CAu > 2 solutions, re-spectively. They are characterised by enthalpy and entropy of PT and interpreted as a result of relations between the proton transfer and solvation phenomena. In strongly cooled CB : CAH Ť 2 solutions the intra-complex proton motion is probably coupled to the motion of the solvating base molecule. This phenomenon is qualitatively described by the density function of the energy attraction between the bridging AHB proton and the solvating amine molecule. In the CB : CAH > 2 solutions this mechanism does not work probably and the hydrogen bonded ion-pairs are strongly solvated by the neighbour amine molecules.