Molecular equilibria investigations in 3-acetylpyridine using non-linear dielectric effect and dipole moment measurements

The dipole moment and non-linear dielectric effect for diluted solutions of 3-acetylpyridine were studied within the temperature range 288–323 K in six solvents of different polarity. Taking into account the trans-cis equilibrium and dimerization the enthalpy and entropy were calculated directly from the experimental data and under the assumption that the polarity of the environment is independent of temperature. Significant differences in the values of thermodynamical functions were found to be strongly dependent on the method used. The results obtained showed a higher stability of the polar cis conformer in more-polar environments. It was also shown that the relatively stable dimers of 3-acetylpyridine appearing in non-polar solvents when transferred to more-polar environments become unstable and their structure is no longer well defined.