IDEAL-GAS THERMODYNAMIC PROPERTIES OF SULFUR HETEROCYCLIC-COMPOUNDS

The available structural parameters, fundamental frequencies and entha lpies of formation for thiirane, thiirene, thietane, 2H-thiete, 1,2-di thiete, tetrahydrothiophene, 2,3-dihydrothiophene, 2,5-dihydrothiophen e, thiophene, 1,2-dithiolane, 1,3-dithiolane, 1,2,4-trithiolane, tetra hydro-2H-thiopyran, 5,6-dihydro-2H-thiopyran, 1,3-dithiane, 1,4-dithia ne, 1,4-dithiin, 1,3,5-trithiane, thiepane and 1,3,5,7-tetrathiocane w ere critically evaluated and recommended values were selected. Molecul ar constants and enthalpies of formation for some of the molecules wer e estimated, as experimental values for these compounds are not availa ble. Using the rigid-rotor harmonic-oscillator approximation, this inf ormation was used to calculate the chemical thermodynamic functions, C -p(o), S-o, -(G(o)-H-0(o))/T, H-o - H-0(o), and the properties of form ation, Delta(f)H(o), Delta(f)G(o), log K-f(o), to 1500 K in the ideal gas state at a pressure of 1 bar. The contributions to the thermodynam ic properties of compounds having inversion motion (thietane, 2,3- and 2,5-dihydrothiophene) or pseudo-rotation (tetrahydrothiophene) have b een computed by employing a partition function formed by the summation of the inversional or pseudo-rotational energy levels. These energy l evels have been calculated by solving the wave equation using appropri ate potential functions. The calculated values of the thermodynamic fu nctions are compared with those reported in other works. Comparison wi th experimental data, where such are available, is also presented. The thermodynamic properties for twelve of the compounds are reported for the first time. (C) 1995 American Institute of Physics and American C hemical Society.