Structural effects on the thermochemical properties of sulfur compounds:: I.: Enthalpy of combustion, vapour pressures, enthalpy of sublimation, and standard molar enthalpy of formation in the gaseous phase of 1,3-dithiane

A rotating-bomb combustion calorimeter specifically designed for the study of sulfur-containing compounds has been assembled and calibrated. Thianthrene has been used as a secondary standard in order to verify the chemistry of the combustion process and the accuracy of the energy corrections involved in the analysis of the results. With this calorimeter, the energy of combustion of 1,3-dithiane has been determined. The vapour pressure of 1,3-dithiane has been measured over a temperature range of about 15 K by the Knudsen effusion technique. From the experimental results, the following quantities for 1,3-dithiane at T = 298.15 K have been derived: Delta(f)H(m)(0)(cr) = -(65.6 +/- 2.2) kJ.mol(-1) Delta(sub)H(m)(0) - (62.9 +/- 0.7) kJ.mol(-1),and Delta(f)H(m)(0)(g) = -(2.7 +/- 2.3) kJ.mol(-1) A comparison of these results with data for 1,3-dioxane and other reference molecules was carried out. (C) 1999 Academic Press.