Ultrasonic Investigation of Acetic Acid Hydrogen Bond Formation. I. Acetic Acid–Acetone Solutions

Ultrasonic absorption has been measured in acetic acid–acetone mixtures in the concentration range $\text{5.47M}$ acetic acid to $\text{17.38M}$ (glacial). The frequency range covered was 0.5–30 MHz, and all the systems fit a single relaxation mechanism. It is demonstrated that the chemical process responsible for the relaxation is an equilibrium of the form $$\mathrm{D\hspace{0.17em}\rightleftarrows }{\displaystyle {lim}_{k_r}^{k_f}}\mathrm{\hspace{0.17em}C,}$$ where $D$ and $C$ are believed to be the “closed” (two H bond) and “open” (one H bond) forms of the acetic acid dimers. This scheme gives a quantitative fit of the ultrasonic data and complete thermodynamic and kinetic parameters if the rate constants are assumed to be viscosity dependent.