Hydrogen bonding and chain conformational isomerization of alcohols probedby ultrasonic absorption and shear impedance spectrometry

The acoustical absorption spectra between 300 kHz and 3 GHz and the complex shear viscosity spectra between 6 and 120 MHz for some monohydric alcohols are reported. The acoustical spectra exhibit two relaxation regions, one l ocated at frequencies around some hundred MHz and the other one around some GHz. The shear viscosity spectra reveal a relaxation process in conformity with the low-frequency acoustical relaxation. This relaxation is assigned to fluctuations in the structure of hydrogen bonded alcohol clusters. The h igh-frequency acoustical relaxation is discussed in terms of a damped torsi onal oscillator model of allkyl chain isomerization, corresponding with the rotational isomerization of n-alkanes. The high frequency (>5 GHz) shear v iscosity of the alcohols is estimated and found in the same order (1 mPa s) as that for n-alkanes.