Synthesis of polyynes in a submerged electric arc in organic solvents Original Research Article

The products formed by the electric arc between graphite electrodes submerged in organic solvents like acetonitrile, n-hexane and methanol consist of a series of polyynes having the general chemical structure: H(CC)mH (with m an integer 1,2,3,…m). The polyynes were separated through liquid chromatography (HPLC) and identified through their characteristic electronic absorption spectra recorded by a diode-array detector. When acetonitrile was arced at −40 °C, the entire polyynes series to m=9 (chain with 18 carbon atoms) were produced. Instead, at room temperature the entire polyynes series to m=8 (chain with 16 carbon atoms) were obtained. Similar results were obtained by arcing graphite electrodes in n-hexane and in methanol. The purest polyynes mixture is obtained in methanol while in n-hexane and in acetonitrile by-products are formed together with the polyynes series. In particular, in acetonitrile, a series of monocyanopolyynes was detected together with the normal polyynes series.