Equilibria between Sulfur Rings in Carbon Disulfide Solution at Elevated Temperatures

Abstract

<jats:title>Abstract</jats:title><jats:p>Cyclooctasulfur, S<jats:sub>8</jats:sub>, dissolved in CS<jats:sub>2</jats:sub> reacts at 130-155 °C in sealed ampoules to give S<jats:sub>6</jats:sub> and S7 whose concentrations have been determined by HPLC. The half-time of the reaction is independent of the initial S<jats:sub>8</jats:sub> concentration and decreases from 232 min at 130 °C to 64 min at 150 °C. After long reaction times equilibrium concentrations are observed which are in agreement with the law of mass action. From the temperature dependence of the equilibrium constants the following reaction enthalpies (at 130-155 °C) have been calculated: </jats:p><jats:p>3/4S<jats:sub>8</jats:sub>⇌S<jats:sub>6 </jats:sub>⊿H°=24kJ/mol</jats:p><jats:p>7/8S<jats:sub>8</jats:sub>⇌S<jats:sub>7 </jats:sub>⊿H°=21kJ/mol</jats:p>

Raman Spectrometric Study of the Composition of Sulfur Vapor at Temperatures up to 700°C

“…Their value of 24.6 kJ mol :' for the standard heat of formation of S7 is in fact not in agreement with two more recent determinations which resulted in 21 kJ mol-1 for S7 dissolved in CS 2 (130-155°C) [61] and 21.2 kJ mol-I for S7 dissolved in liquid sulfur (116-159°C) [60]. These differences between the vapor and solution data are not caused by intermolecular interactions in the latter case since the corresponding enthaipies for the Comparison of the ratios xi/xs obtained through Rau's model [59] (i = 7 full line, i = 6 dotted line), and xi/xs calculated from Raman spectroscopy data (i = 7: -.…”

The Chemistry of Organic Polysulfanes R−Sn−R (n > 2)

“…In the nonpolar solvent carbon disulfide, the equilibrium can be more rapidly established (within hours) by heating to 130-155 °C. 274 Under these conditions up to 7 mol % S 7 and 2 mol % S 6 were observed at a total sulfur concentration of 0.3 mmol g -1 (solution); the reaction was found to be of first order with an Arrhenius activation energy of 95 kJ mol -1 . In highly purified methanol as used for HPLC analysis, the reaction rate is much lower than in commercial solvents even if the producer claims "chromatographic purity".…”

Application of Dicyanohexasulfane for the Synthesis of cyclo-Nonasulfur. Crystal and Molecular Structures of S6(CN)2 and of α-S91

“…c -S 9 is a component of liquid sulfur, which is industrially produced on a very large scale; S 9 is also formed on UV irradiation of S 8 or S 7 in CS 2 solution at 25 °C, on heating of S 8 in CS 2 solution to 130−155 °C, and on thermal depolymerization of industrially produced polymeric sulfur (“μ-sulfur”) in the presence of an organic solvent like cyclohexane or carbon disulfide . Traces of S 9 have also been detected in certain commercial samples of elemental sulfur consisting mainly of S 8 .…”