Dielectric Relaxation and Intermolecular Association of Alicyclic Alcohols in Liquid and Solid States

The dielectric constants and losses of cyclopentanol (CPEN), cyclohexanol (CHEX), cycloheptanol (CHEP), and cyclooctanol (COCT) have been measured at frequencies from 1.35 to 4500 MHz over a temperature range of 10–35°C. The absorption could be resolved into three Debye-like dispersion regions in liquid and solid states. The relaxation time of the first, low-frequency, dispersion region and viscosity for CHEX are slightly larger than those for CHEP. This observation can be connected with differences of the molecular geometry between a chair and a twisted chair form and an interconversion between an equatorial and an axial form. Upon solidification, the magnitude of the first dispersion region decreases from 12.67 in the liquid state to 10.25 in the solid state for CHEX and increases from 8.77 to 9.35 for COCT. A transformation from a linear chain polymer into a nonpolar cyclic polymer for CHEX and from a linear chain polymer into a chain dimer and trimer for COCT, occurs mainly upon solidification. The free energies of activation in the solid state are 26 kJ mol−1 for the first region, 23 kJ mol−1 for the second region, and 17 kJ mol−1 for the third region and are larger than those in the liquid state, respectively.