Reactions of diazoalkanes upon metallic surfaces: Polymer formation and a stereoregulating action of gold

Abstract

AbstractEarlier investigations are reported on the decomposition of diazomethane in ethereal solution, in the presence of gold chloride as a catalyst: these have shown that the catalytic activity in obtaining polymethylene from the diazo compound is due to gold metal.The catalytic action of gold under similar conditions upon diazoethane has brought to the formation of crystalline polyethylidene, obtained by the authors for the first time. The gold surface, then, in the present case, exhibits a stereoregulating activity in the reaction.These results led the authors to investigate more thoroughly the polymerizing action of different metal surfaces, prepared as evaporated films, on the first terms of the diazoalkane series.The main results are reported as obtained by following the reaction with the help of chromatographic analyses of the gases, liberated aside of nitrogen. The present remarks have been made:The following metals, in decreasing order of yield, give amorphous polymers: Cu, Ti, Fe, Mg, W, Ni, Mn, V, Ta, Pt, Co, Zn, Cd, Au, Cr, Al, whilst Mo, Pd, Rh, Zr, Ag, give practically no polymer, although causing the decomposition of the diazo compound. These experiments are related to diazoethane in ethereal solution.It is confirmed that gold only, among the metals tried up to the present, shows a stereospecific action in the formation of polymer from diazoethane.The chromatographic analysis of the gases developed from the decomposition of diazoethane on the following metals: Pd, Ag, Mo, Cu, Au, show that, the surfaces catalyzing polymer formation give out chiefly the butenes‐2, with small quantities of ethylene, whilst the metals not forming polymer develop chiefly ethylene together with small quantities of ethane.For the first time, still by the action of gold metal surfaces, apparently crystalline polymers from diazopropane and diazobutane have been obtained, showing that the stereospecific action of gold, looks not to be limited to the only case of diazoethane, but to be valid also for the higher terms of the series with formation of apparently stereoregular polymers of the type CHRCHRCHR, where R is a chemical group.The crystalline structure of polyethylidene is discussed.The following infrared spectra are reported: (a) of gaseous diazoethane (whose structure is discussed); (b) of amorphous polybutylidene; (c) of the crystalline polymers obtained from the corresponding diazoalkanes, namely polyethyl‐, polypropyl‐, polybutylidene. Some simple schemes for the reaction paths, drawn from the present experimental data, are suggested.