Carbon Subsulphide Polymer (C₃S₂) _X Formation by Arcing Carbon disulphide with the Submerged Carbon Arc

Summary

Arcing of liquid carbon disulphide between graphite electrodes at  − 80 °C produces elemental sulphur, carbon subsulphide (C₃S₂) having the structure S=C=C=C=S, and three other molecular species whose structure remains unassigned. The results were obtained by liquid chromatography (HPLC) equipped with a diode array detector. No polyynes were detected by HPLC although they form in other solvents by arcing graphite electrodes. It has been proposed that carbon subsulphide is obtained from the interaction between carbon monosulphide (C=S) formed from the plasmalysis of CS₂ with C₂ vapour released by the graphite electrodes. C₃S₂ has been identified in the arced CS₂ solution from its characteristic FT-IR absorption bands at 2059 and 1019 cm⁻¹. During warm-up from  − 80 °C to room temperature, the red CS₂ solution with C₃S₂ becomes dark brown and a polymeric product, polycarbon subsulphide (C₃S₂) _X , separates. This polymerization reaction was followed spectroscopically for the first time showing that the disappearance of the characteristic C₃S₂ FT-IR bands are accompanied by the appearance of typical carbon subsulphide polymer bands. The FT-IR spectrum of the polymeric product confirms that it is essentially composed by (C₃S₂) _X , although (CS₂) _X polymer is also identified as minor component. The FT-IR spectrum of the polymeric product does not appear significantly different from the spectra of the polymeric products obtained from photolysis, radiolysis, and sonolysis of CS₂. The thermal behaviour of the polymeric product obtained from arcing CS₂ has been studied by differential scanning calorimetry in static air. No melting point and other transitions are detected until 536 K; at 543 K a sharp exothermal transition occurs.