Electroreduction of but-2-yne on a platinum electrode in sulphuric acid solution

Abstract

The electroreduction of but-2-yne on platinized Pt electrode in 1 mol dm^–3 H₂SO₄ or D₂SO₄ solution has been studied. Selectivities, reaction rates and deuterium distributions in products have been observed by gas chromatography and mass spectrometry. The main products are butane, cis- and trans but-2-enes with a current efficiency of ca. 100% in total. Their selectivities depend sharply on potential in good agreement with their behaviour in the Tafel plot. The distributions of the deutero-species in cis-but-2-ene and butane show that but-2-yne is reduced to cis-but-2-ene by the simple addition of hydrogen atoms, whereas the route to butane is different. In the latter route, there exist two paths which consist of an extremely fast and a moderate exchange reaction of the isotope. The distributions are simulated satisfactorily by this dual-path model.