Intermediates in the decomposition of aliphatic diazo-compounds. Part 16. Catalysis of the decomposition of diazodiphenylmethane by copper(I) bromide, iodide, and perchlorate in acetonitrile

Abstract

The kinetics and products of decomposition of diazodiphenylmethane catalysed by copper(I) bromide, iodide, and perchlorate in acetonitrile solution have been investigated. All three salts convert the diazo-compound almost wholly into benzophenone azine, but small quantities of benzophenone are also produced. Copper(I) bromide and perchlorate both give rise to reactions showing the simple kinetic form v=k[Cu^I][Ph₃CN₂], but the rate of decomposition of diazodiphenylmethane in the presence of copper(I) iodide is apparently independent of the concentration of the diazo-compound, although substituents therein alter the rate coefficient. Small amounts of paramagnetic precipitates form in reactions catalysed by the copper(I) halides, and reaction solutions are coloured when decomposition of the diazoalkane is complete. For a given catalyst concentration the order of catalytic efficiencies is Cul > CuBr > CuClO₄.

It is shown that the rate coefficients observed in reactions catalysed by copper(I) bromide can be predicted with reasonable accuracy by an equation previously developed for copper(II) bromide catalysis. The relevance of this and the other findings to previous mechanistic studies is discussed.