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1 Polish Journal of Chemistry

1 1998

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Applications of linear and non-linear polarization to conformational equilibria studies

Małecki J., Nowak J.

Polish Journal of Chemistry

1998

Vol. 72, nr 2

210-229

Applications of linear and non-linear dielectric effects to studies of intramolecular equilibria in liquids are described. The physical principles of the two phenomena being responsible for the magnitude of the observed effect, i.e. the Langevin effect and the chemical effect, are outlined. The later effect consists in shifting the molecular equilibria under an influence of electric field to favour the more polar products of reaction. The experimental set-up and its limitations are shortly described. Applications of Non-linear Dielectric Effect (NDE) to determine the changes in free energy, enthalpy and entropy of fast intermolrcular equilibria are described and illustrated by selected examples. The significance of the solvent polarity and its dependence on temperature in enthalpy and entropy is analyzed. Two opposite approaches to calculate these quantities are presented: directly from experomental data according to the usually applied procedure and under the assumption of a constant polarity. Presented experimental results illustrate the physical meaning of these quantities and the significance of the applied approach to the interpretation of experimental results.