Deuterium isotope differences in 2-propanone, (CH3)2CO/(CD3)2CO: a high-pressure sound-speed, density, and heat capacities study

A new high-pressure, non-intrusive ultrasonic microcell [J. Chem. Thermodyn. 36 (2004) 211-222] was used to carry out sound-speed measurements in deuteriated 2-propanone (acetone-d6) in broad ranges of temperature (288 < T/K < 338) and pressure (0.1 < p/MPa < 160). To the best of our knowledge, there are no data regarding speed of sound of acetone-d6. (p, ρ, T) data for acetone-d6 were also determined but in a narrower T, p range (298 to 333 K; 0.1 to 60 MPa). In this interval, several thermodynamic properties were thus determined, such as: isentropic (κs) and isothermal (κT) compressibility, isobaric thermal expansivity (αp), isobaric (cp) and isochoric (cv) specific heat capacity, and the thermal pressure coefficient (γv). Comparisons with our data for acetone-h6 enabled us to establish the magnitude and sign of deuterium isotope effects for identical properties. These effects are a consequence of distinct vibrational mode frequencies in an isotope-invariant force constants' field. Molar heat capacities and their isotope effects were theoretically determined by employing an Einstein-like model for the vibrational frequencies of acetone-h6 and acetone-d6.