Thermodynamic and magnetic studies on the formation of gem-diol in an aldehyde-water mixture

Article abstract of DOI:10.1246/bcsj.72.975

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 x 10^-6 cm³ mol^-1 and -51.5 x 10^-6 cm³ mol^-1 at 287 K, respectively.