The surface chemistry of diethyl disulfide on copper

The surface chemistry of diethyl disulfide (DEDS) is studied on polished copper foils and a Cu(111) single crystal, using temperature-programmed desorption, reflection absorption infrared spectroscopy and X-ray photoelectron spectroscopy. A portion of the DEDS reacts to form ethyl thiolate species even at ~ 80 K, where reaction is complete on heating to ~ 200 K. The resulting thiolate species decompose to form either ethylene or ethane at ~ 380 to ~ 400 K. The selectivity to ethane increases relative to ethylene formation at higher coverages, due to surface crowding that inhibits β-hydride elimination reactions thereby lowering the ethylene yield. Such a change in orientation is confirmed by changes in relative intensities of the ethyl group vibrational modes with coverage.