Ultrasonic absorption in relation to hydrogen bonding in solutions of alcohols. 2. Ultrasonic relaxation spectra of solutions of alcohols in cyclohexane

Abstract

The ultrasonic absorption of solutions of ethanol, 1-butanol, 1-octanol, 1-dodecanol, 1-hexadecanol, 3-octanol, 2-methyl-3-heptanol, and 2,4-dimethyl-3-hexanol in cyclohexane at 25 °C has been measured in the frequency range 4-250 MHz. The relaxation spectra of all of the investigated solutions could be fitted to a relaxation equation with a single relaxation frequency. The results have been interpreted on the basis of a reaction mechanism where n alcohol molecules associate to give cyclic and noncyclic n-mers. The absorption is attributed to the perturbation by the sound waves of the association equilibrium leading to noncyclic n-mers. For all primary alcohols no fit to the data could be obtained for = 3 but equally good fits were obtained for = 4 and n-5, except with 1-hexadecanol for which = 5 provides the best fit. The results indicate that (1) the rate of association of alcohol molecules through H bonds is close to its diffusion-controlled limit, even for the most hindered alcohol investigated; (2) the dissociation rate constant of one alcohol molecule from a noncyclic rc-mer is only very slightly dependent on the alcohol chain length for primary alcohols. This rate constant increases with the degree of steric hindrance, reflecting the decreased stability of noncyclic aggregates. For 2methyl-3-heptanol the best fit to the data is obtained for = 3. Likewise, the results for 2,4-dimethyl-3-hexanol appear to indicate that the association of this alcohol is essentially restricted to dimerization. Larger associated species appear to be present only in very small amount. The relation between ultrasonic absorption data and dipole moment data for octanol solutions is examined.

Effect of salinity on the ultrasonic absorption and flow birefringence of microemulsions

“…The upper phase is essentially a solution of butanol in toluene (concentration of about 0.5 M at S > 8 %) with a small amount of dissolved water [15]. The ultrasonic absorption of solutions of alcohols in organic solvents (including butanol in toluene) has been extensively investigated [37][38][39]. The results indicate that concentrated solutions of butanol in toluene (such as the upper phase) would have relaxation frequencies well above 150 MHz, thereby explaining the near constancy of the absorption of the upper phase at f 120 MHz.…”

Relaxation rate and scaling function of the critical system 3-methylpentane-nitroethane-cyclohexane

“…8,11,60 Since it is largely masked by the large critical contributions to the present spectra an assignment of the term to a molecular process is impossible. 8,11,60 Since it is largely masked by the large critical contributions to the present spectra an assignment of the term to a molecular process is impossible.…”

Ultrasonic measurements on the solutions of lanthanum and cerium soaps in non-aqueous medium

“…The study of molecular interactions has been a subject of extensive investigations by IR [1,2], Raman [3], NMR [4,5] and ultrasonic absorption [6,7] measurements. Several workers have used ultrasonic velocity measurements for studying the ion-solvent interaction and solvation of salts in non-aqueous solvents.…”