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. Thianthre ne has been used as a secondary standard in order to verify the chemistry o f the combustion process and the accuracy of the energy corrections involve d in the analysis of the results. With this calorimeter, the energy of comb ustion of 1,3-dithiane has been determined. The vapour pressure of 1,3-dith iane has been measured over a temperature range of about 15 K by the Knudse n effusion technique. From the experimental results, the following quantiti es 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 re sults with data for 1,3-dioxane and other reference molecules was carried o ut. (C) 1999 Academic Press.