High performance liquid chromatography analysis of electrolysis solutions : a study of the reduction of carbon disulfide

Addition of methyl iodide to a sample of the electrolysis solution converted ionic multisulfur species to molecular species which were retained by an octadecylsilane (ODS) column operated in the reverse phase mode. A solution of 50:50 methanol and water was employed as the mobile phase. A spectrophotometric detector set at 330 or 412 nm was used.

The chromatograms of the reduction solution show evidence of six products. Two of the products were identified as 4,5-bis(methylthio)- l,3-dithiolen-2-thione, the major product of this reduction, and dimethyl trithiocarbonate. A third product is thought to be 4,5—bis(methylthio)— l»2>4-thithiolen-3-thione. These have all been reported in the literature. One major and two minor products were observed which are not yet identified and have not been reported in the literature. It is speculated that the major unidentified product, which is shown by chromatograms to decompose with time to give the trithiocarbonate as one of the decomposition products, is demethyl orthothiooxalate or a compound of similar structure. The HPLC analysis showed that there were only minor variations in the relative amounts of the major products as the carbon disulfide electrolysis proceeded.

The zinc(II) complex of the dianion of 4,5-dimercapto-l,3-dithiolen-2-thione (C₃S₅^2-)was prepared. It was used in the synthesis of gram quantities of ethylene-4,5-dimercapto-l,3-dithiolen-2-thione by the addition of 1,2-dibromoethane to a refluxing acetone solution of the complex. HPLC analysis was employed to monitor the alkylation step and the ether extraction step used in purifying the thione.

The electrochemical reduction and the alkaline hydrolysis of ethylene-4,5-dimercapto-l,3-dithiolen-2-thione was studied in hopes of preparing a zinc(II) complex of the dianion, 1,4-dithia-2-cyclohexene2,3-dithiolate. It was found that the dianion was not formed in the electrochemical reduction, at least not at synthetically useful con centrations.