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 5.47M acetic acid to 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 D ⇄ lim krkf 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.