Acoustic Relaxations in Toluene and Alcohols in the Frequency Range of 10 to 300 kHz Measured by the Resonance Reverberation Method

The acoustic absorption in toluene at frequencies 10 to 300 kHz is measured by the improved resonance reverberation method. The relaxation is found around 100 kHz (20°C). The relaxation strength increases and the relaxation frequency shifts toward high with increasing temperature. The relaxation is assigned to the coupling of translational motion of molecules with intramolecular vibration of C-H stretching in the methyl group. A good agreement between experiment and theory is obtained in the relaxation strength over covered temperatures. The absorption coefficient of acoustic waves in n-BuOH, i-BuOH and t-BuOH is measured by the same technique as in toluene. The relaxation is observed around 30 kHz (n-BuOH), 20 kHz (i-BuOH), and below 10 kHz (t-BuOH) at 30°C. The activation energy is 8.7 and 9.4 kcal/mole for n-BuOH and i-BuOH, respectively. The relaxation strength decreases with increasing temperature. The relaxation is interpreted in terms of the reaction between associated complexes, cyclic polymer and cyclic dimers.