Physico-chemical studies on acetaldehyde polymerization at high pressure and low temperature : I. Liquid-solid transition and polymerization of acetaldehyde

Acetaldehyde polymer is obtained with no catalyst at low temperature by applying high pressure to acetaldehyde. In order to obtain the acetaldehyde polymer, there is the limiting pressure at each reaction temperature, and the acetaldehyde polymer is not obtained by the pressure lower than this limiting pressure. In the experimental range, plotting the limiting pressure against reaction temperature, the linear relation is obtained. At the pressures above and below this limiting pressure, the volume change of acetaldehyde is measured. Since the discontinuity of the volume change of acetaldehyde is found at the limiting pressure, the temperature and the limiting pressure are identified as the transition temperature and pressure of acetaldehyde. The values of -3.53, -3.84, -4.27 and -4.58ml/mole are obtained as the volume decreases of acetaldehyde of the liquid-solid transition at temperatures -50, -60, -70 and -78℃, respectively. Using the Clausius-Clapeyron equation ΔH_T and ΔS_T are calculated from the ΔV_T as -2.40～-2.11 kcal/mole, and -12.3～-9.47cal/deg. mole, respectively. The ΔH_T and the ΔS_T increase with temperature and pressure. The acetaldehyde polymer formed by this polymerization is found as the atactic polyether type polymer by the infrared spectrum and the solubility in the solvents. The values of -13.2～-12.1ml/mole are obtained as the volume decreases of the polymerization of acetaldehyde at temperature -50～-78℃. The values are in good agreement with the value obtained from the calculation