Equilibrium vapour pressures of tetraorganostannanes

Abstract

Equilibrium vapour pressures (40° to 120°C) of tetraorganostannes have been measured by a capillary gas chromatography method. By extrapolation, values at 20°C have also been determined. Tetramethylstannane was chosen as the reference compound. Under the experimental conditions employed, tetra-n-butylstannane was the largest compound whose vapour pressure could be determined. Current vapour pressure estimation methods for hydrocarbons proved satisfactory for tetraalkylstannanes, but less successful for tetraalkenylstannanes. The logarithms of measured organostannane vapour pressures together with literature values for hydrocarbons and organoplumbanes form three parallel but distinct relationships with molecular weight. In contrast, for vapour pressures of organostannanes and hydrocarbons, a single unique relationship is found with intrinsic molar volume. Enthalpies of vaporization, and where appropriate boiling point information was available, entropies of vaporization for the tetraorganostannanes were also derived. For enthalpy of vaporization a similar situation to vapour pressure exists. Two roughly parallel but distinct relationships were observed for hydrocarbons and organostannanes when plotted against molecular weight, but only one with intrinsic molar volume.