Thermodynamic and Magnetic Studies on the Formation of gem-Diol in an Aldehyde–Water Mixture

A thermodynamic study on the formation of gem-diol in an aldehyde–water mixture was carried out by NMR measurements. The equilibrium constants for the formation of gem-diol were determined at 280.3—298.4 K. From the relationship between the equilibrium constant and the temperature, ΔH and ΔS were obtained to be −20.4 kJ mol−1 and −101 J K−1 mol−1 in the case of acetaldehyde, and −22.9 kJ mol−1 and −110 J K−1 mol−1 in the case of propionaldehyde, respectively. It is difficult to isolate the gem-diol from an aldehyde–water mixture. The diamagnetic susceptibility of gem-diol was estimated by measuring the susceptibilities of the aldehyde–water mixture at various molar ratios. The diamagnetic susceptibility was determined using Gouy’s method. The diamagnetic susceptibilities of 1,1-ethanediol and 1,1-propanediol were −39.1 × 10−6 cm3 mol−1 and −51.5 × 10−6 cm3 mol−1 at 287 K, respectively.