Dielectric Relaxation in Isomeric Octyl Alcohols

Abstract

The dielectric constant and loss of eight isomeric octanols has been measured over a wide range of temperature and frequency. Two distinctly different types of dispersion loci are found: For those alcohols whose –OH group is so sterically hindered that association into linear chains is unfavorable, a very small, very broad dispersion, characterized by relatively short relaxation times, is found. For less hindered species, the low‐frequency, relatively slow, dispersion is Debye‐like, and two high‐frequency dispersion regions have been resolved in two compounds. The molar activation energies for all three dispersion regions are closely similar and ${\tau }_1{\mathrm{:\tau }}_2{\mathrm{:\tau }}_3\text{\hspace{0.17em}∼\hspace{0.17em}100:10:1}$ . The activation energy for the principal (Debye‐like) dispersion is strongly dependent on the steric hindrance of the –OH group. Activation energies vary from about 8 to 20 kcal so that rupture of a hydrogen bond is an unlikely rate‐determining step.