Dielectric Relaxation of Liquid Alicyclic Alcohols

Abstract

The dielectric spectra of liquid cyclopentanol, cyclohexanol, cycloheptanol and cyclooctanol are reported for frequencies up to 72 GHz and temperature 20 (cyclohexanol solid), 30 and 40 °C. The absorption spectra are peculiar in exhibiting a remarkably developed high frequency shoulder which is attributed to single molecule and internal motion, while the principal absorption is due to association as with other alcohols.Although numerous dielectric relaxation studies on different kinds of liquid alcohols have been reported, alicyclic ones have received only little attention. Cyclohexanol has been examined in nonpolar solvents [1], which work was extended recently to some very high spot frequencies (< 670 GHz) [2], On ther other hand, the solid state dielectric properties have attracted attention. These, for example, have been measured at frequencies covering the solid state absorption region (at < 13 MHz [3, 4]) over a very broad temperature and pressure range. Those studies yielded also some results on the liquid state [5], An investigation of pure liquid cycloalcohols by Shinomiya [6] was restricted to frequencies covering the principal absorption region (< 4.5 GHz). It seems therefore worthwhile to reconsider the dielectric properties of pure cycloalcohols (at normal pressure) and to extend measurements over a broader frequency band in order to gain information also on possible higher frequency relaxation contributions. Here we report dielectric relaxation data of four alicyclic alcohols, cyclopentanol (C 5 ) to cyclooctanol (C 8 ), as measured up to 72 GHz. In relation to the literature quoted, our results complement the hitherto known lower frequency part of the dielectric spectrum of pure cycloalcohols [5,6] and also the solution results for cyclohexanol [2].Substances obtained from Fluka and Merck were used without further purification. Residual water contents < 0.5 percent should, according to experiences with various alcohol-water systems [7], not yet significantly influence the relaxation parameters. The complex permittivity was determined by use of various Reprint requests to Prof. M. Stockhausen,

Study of the nature of glass transitions in the plastic crystalline phases of cyclo-octanol, cycloheptanol, cyanoadamantane and cis-1,2-dimethylcyclohexane

“…46͒. This process was referred to as the third process in their paper 46 ͑and in our Fig. 4 as well͒.…”

Relaxation dynamics in plastic crystals

“…17 There is a large number of investigations of this material using different techniques, 17,53-59 including dielectric spectroscopy. [55][56][57][58][59] For the rather complex phase diagram of cyclo-hexanol the reader is referred, e.g., to Ref. 55.…”

Study of secondary relaxation in disordered plastic crystals of isocyanocyclohexane, cyanocyclohexane, and 1-cyanoadamantane

“…20 the origin of ␤ process is still debated. On one hand, alcohols demonstrate multiple relaxation processes 21 attributable to intramolecular motions such as the -OH group relaxation, while on the other in glassy crystals of hexasubstituted bezenes, no clearly resolvable ␤ process is observed. [22][23][24] In this context, 1-cyanoadamantane ͑CNADM͒ ͑C 10 H 15 CN, T g = 168.4 K͒ and cyanocyclohexane ͑CNCH͒ ͑C 6 H 11 CN, T g = 135.6 K͒ in which the main dipole is situated in the side group -C w N, and isocyanocyclohexane ͑ICNCH͒ ͑C 6 H 11 NC, T g = 131.3 K͒ with the main dipole connected to the cyclohexyl ring as -N w C should prove to be interesting; the corresponding activation energy of the ␤ process should reveal if the process is effected by the type of side group of the molecules.…”